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Thu, 30 Nov 2023 00:00:00 -0500

With a quantum “squeeze,” clocks could keep even more precise time, MIT researchers propose
Posted on Thursday November 30, 2023

Category : Light

Author : Jennifer Chu | MIT News

More stable clocks could measure quantum phenomena, including the presence of dark matter.

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The practice of keeping time hinges on stable oscillations. In a grandfather clock, the length of a second is marked by a single swing of the pendulum. In a digital watch, the vibrations of a quartz crystal mark much smaller fractions of time. And in atomic clocks, the world’s state-of-the-art timekeepers, the oscillations of a laser beam stimulate atoms to vibrate at 9.2 billion times per second. These smallest, most stable divisions of time set the timing for today’s satellite communications, GPS systems, and financial markets.

A clock’s stability depends on the noise in its environment. A slight wind can throw a pendulum’s swing out of sync. And heat can disrupt the oscillations of atoms in an atomic clock. Eliminating such environmental effects can improve a clock’s precision. But only by so much.

A new MIT study finds that even if all noise from the outside world is eliminated, the stability of clocks, laser beams, and other oscillators would still be vulnerable to quantum mechanical effects. The precision of oscillators would ultimately be limited by quantum noise.

But in theory, there’s a way to push past this quantum limit. In their study, the researchers also show that by manipulating, or “squeezing,” the states that contribute to quantum noise, the stability of an oscillator could be improved, even past its quantum limit.

“What we’ve shown is, there’s actually a limit to how stable oscillators like lasers and clocks can be, that’s set not just by their environment, but by the fact that quantum mechanics forces them to shake around a little bit,” says Vivishek Sudhir, assistant professor of mechanical engineering at MIT. “Then, we’ve shown that there are ways you can even get around this quantum mechanical shaking. But you have to be more clever than just isolating the thing from its environment. You have to play with the quantum states themselves.”

The team is working on an experimental test of their theory. If they can demonstrate that they can manipulate the quantum states in an oscillating system, the researchers envision that clocks, lasers, and other oscillators could be tuned to super-quantum precision. These systems could then be used to track infinitesimally small differences in time, such as the fluctuations of a single qubit in a quantum computer or the presence of a dark matter particle flitting between detectors.

“We plan to demonstrate several instances of lasers with quantum-enhanced timekeeping ability over the next several years,” says Hudson Loughlin, a graduate student in MIT’s Department of Physics. “We hope that our recent theoretical developments and upcoming experiments will advance our fundamental ability to keep time accurately, and enable new revolutionary technologies.”

Loughlin and Sudhir detail their work in an open-access paper published in the journal Nature Communications.

Laser precision

In studying the stability of oscillators, the researchers looked first to the laser — an optical oscillator that produces a wave-like beam of highly synchronized photons. The invention of the laser is largely credited to physicists Arthur Schawlow and Charles Townes, who coined the name from its descriptive acronym: light amplification by stimulated emission of radiation.

A laser’s design centers on a “lasing medium” — a collection of atoms, usually embedded in glass or crystals. In the earliest lasers, a flash tube surrounding the lasing medium would stimulate electrons in the atoms to jump up in energy. When the electrons relax back to lower energy, they give off some radiation in the form of a photon. Two mirrors, on either end of the lasing medium, reflect the emitted photon back into the atoms to stimulate more electrons, and produce more photons. One mirror, together with the lasing medium, acts as an “amplifier” to boost the production of photons, while the second mirror is partially transmissive and acts as a “coupler” to extract some photons out as a concentrated beam of laser light.

Since the invention of the laser, Schawlow and Townes put forth a hypothesis that a laser’s stability should be limited by quantum noise. Others have since tested their hypothesis by modeling the microscopic features of a laser. Through very specific calculations, they showed that indeed, imperceptible, quantum interactions among the laser’s photons and atoms could limit the stability of their oscillations.

“But this work had to do with extremely detailed, delicate calculations, such that the limit was understood, but only for a specific kind of laser,” Sudhir notes. “We wanted to enormously simplify this, to understand lasers and a wide range of oscillators."

Putting the “squeeze” on

Rather than focus on a laser’s physical intricacies, the team looked to simplify the problem.

“When an electrical engineer thinks of making an oscillator, they take an amplifier, and they feed the output of the amplifier into its own input,” Sudhir explains. “It’s like a snake eating its own tail. It’s an extremely liberating way of thinking. You don’t need to know the nitty gritty of a laser. Instead, you have an abstract picture, not just of a laser, but of all oscillators.”

In their study, the team drew up a simplified representation of a laser-like oscillator. Their model consists of an amplifier (such as a laser’s atoms), a delay line (for instance, the time it takes light to travel between a laser’s mirrors), and a coupler (such as a partially reflective mirror).

The team then wrote down the equations of physics that describe the system’s behavior, and carried out calculations to see where in the system quantum noise would arise.

“By abstracting this problem to a simple oscillator, we can pinpoint where quantum fluctuations come into the system, and they come in in two places: the amplifier and the coupler that allows us to get a signal out of the oscillator,” Loughlin says. “If we know those two things, we know what the quantum limit on that oscillator’s stability is.”

Sudhir says scientists can use the equations they lay out in their study to calculate the quantum limit in their own oscillators.

What’s more, the team showed that this quantum limit might be overcome, if quantum noise in one of the two sources could be “squeezed.” Quantum squeezing is the idea of minimizing quantum fluctuations in one aspect of a system at the expense of proportionally increasing fluctuations in another aspect. The effect is similar to squeezing air from one part of a balloon into another.

In the case of a laser, the team found that if quantum fluctuations in the coupler were squeezed, it could improve the precision, or the timing of oscillations, in the outgoing laser beam, even as noise in the laser’s power would increase as a result.

“When you find some quantum mechanical limit, there’s always some question of how malleable is that limit?” Sudhir says. “Is it really a hard stop, or is there still some juice you can extract by manipulating some quantum mechanics? In this case, we find that there is, which is a result that is applicable to a huge class of oscillators.”

This research is supported, in part, by the National Science Foundation.


Wed, 29 Nov 2023 11:00:00 -0500

Everything, everywhere all at once
Posted on Wednesday November 29, 2023

Category : School of Humanities Arts and Social Sciences

Author : Sophie Hartley | School of Science

Cosmologist and MLK Scholar Morgane König uses gravitational waves to study the universe’s origins, inflation, and present trajectory.

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The way Morgane König sees it, questioning how we came to be in the universe is one of the most fundamental parts of being human.

When she was 12 years old, König decided the place to find answers was in physics. A family friend was a physicist, and she attributed her interest in the field to him. But it wasn't until a trip back to her mother's home country of Côte d'Ivoire that König learned her penchant for the subject had started much younger. No one in Côte d'Ivoire was surprised she was pursuing physics — they told her she'd been peering upward at the stars since she was a small child, wondering how they all had come together. ­

That wonder never left her. “Everyone looks at the stars. Everyone looks at the moon. Everybody wonders about the universe,” says König. “I’m trying to understand it with math.”

König’s observations have led her to MIT, where in 2021 she continued studying theoretical cosmology as a postdoc with physicist and cosmologist Alan Guth and physicist and historian of science David Kaiser. Now, she is a member of MIT’s 2023-24 Martin Luther King (MLK) Visiting Professors and Scholars Program cohort, alongside 11 others. This year, members of the MLK Scholars are researching and teaching diverse subjects including documentary filmmaking, behavioral economics, and writing children’s books.

Once she was set on physics, König finished her undergraduate studies in 2012, double-majoring in mathematics and physics at Pierre and Marie Curie University in Paris.

Still compelled by questions about the universe, König narrowed in on cosmology, and graduated with her master’s degree from Pierre and Marie Curie in 2014. The way König describes it, cosmology is like archaeology, just up in space. While astronomers study galaxy formations and mutations — all of the stuff in the universe — cosmologists study everything about the universe, all at once.

“It’s a different scale, a different system,” says König. “Of course, you need to understand stars, galaxies, and how they work, but cosmologists study the universe and its origin and contents as a whole.”

From practice to theory

Throughout her studies, König said, she was often the only woman in the room. She wanted to pursue the theories behind cosmology but wasn’t encouraged to try. “You have to understand that being a woman in this field is super, incredibly difficult,” says König. “I told everyone I wanted to do theory, and they didn't believe in me. So many people told me not to do it.”

When König had the opportunity to pursue a PhD in observational cosmology in Marseille and Paris, she almost accepted. But she was more drawn to theory. When she was offered a spot with a little more freedom to study cosmology at the University of California at Davis, she took it. Alongside Professor Nemanja Kaloper, König dove into inflation theory, looking all the way back to the universe's beginning.

It is well-known that the universe is always expanding. Think about inflation as the precursor to that expansion — a quick and dramatic beginning, where the universe grew exponentially fast.

“Inflation is the moment in history that happened right after the beginning of the universe,” says König. “We're not talking about 1 second, not even a millisecond. We are talking 10 to the negative 32nd seconds.” In other words, it took 0.000,000,000,000,000,000,000,000,000,000,01 seconds for the universe to go from something minuscule to, well, everything. And today, the universe is only getting bigger.

Only a sliver of the universe’s composition is understandable using current technology — less than 5 percent of the universe is composed of matter we can see. Everything else is dark matter and dark energy.

For decades, cosmologists have been trying to excavate the universe’s mysterious past using photons, the tiny, particle form of light. Since light travels at a fixed speed, light emitted further back in the universe’s history, from objects that are now farther away from us due to the expansion of the universe, takes longer to reach Earth. “If you look at the sun — don’t do it! — but if you did, you’d actually be seeing it eight minutes in the past,” says König. As they carve their way through the universe, photons give cosmologists historical information, acting as messengers across time. But photons can only account for the luminous 4.9 percent of the universe. Everything else is dark.

Since dark matter doesn’t emit or reflect photons like luminous matter, researchers can’t see it. König likens dark matter to an invisible person wearing a tuxedo. She knows something is there because the tuxedo is dancing, swinging its arms and legs around. But she can’t see or study the person inside the suit using the technology at hand. Dark matter has stirred up countless theories, and König is interested in the methods behind those theories. She is asking: How do you study something dark when light particles are necessary for gathering historical information?

According to König and her MIT collaborators — Guth, the forerunner of inflation theory, and Kaiser, the Germeshausen Professor of the History of Science — the answer might lie in gravitational waves. König is using her time at MIT to see if she can sidestep light particles entirely by using the ripples in spacetime called gravitational waves. These waves are caused by the collision of massive, dense stellar objects such as neutron stars. Gravitational waves also transmit information across the universe, in essence giving us a new sense, like hearing is to seeing. With data from instruments such as the Laser Interferometer Gravitational Wave Observatory (LIGO) and NANOGrav, “not only can we look at it, now we can hear the cosmos, too,” she says.

Black in physics

Last year, König worked on two all-Black research teams with physicists Marcell Howard and Tatsuya Daniel. “We did great work together,” König says, but she points out how their small group was one of the largest all-Black theoretical physics research teams — ever. She emphasizes how they cultivated creativity and mentorship while doing highly technical science, producing two published papers (Elastic Scattering of Cosmological Gravitational Wave Backgrounds and An SZ-Like Effect on Cosmological Gravitational Wave Backgrounds).

Out of the 69,238 people who have earned doctorates in physics and astronomy since 1981, only 122 of them were Black women, according to the National Center for Science and Engineering Statistics. When König finished her PhD in 2021, she became the first Black student at UC Davis to receive a PhD in physics and the ninth Black woman to ever complete a doctorate in theoretical physics in the United States.

This past October, in a presentation at MIT, König ended with an animated slide depicting a young Black girl sitting in a dark meadow, surrounded by warm lights and rustling grass. The girl was looking up at the stars, her eyes full of wonder. “I had to make this with AI,” says König. “I couldn't find an image online of a young Black girl looking up at the stars. So, I made one.”

In 2017, König went to Côte d'Ivoire, spending time teaching school children about physics and cosmology. “The room was full,” she says. Adults and students alike came to listen to her. Everyone wanted to learn, and everyone echoed the same questions about the universe as König did when she was younger. But, she says, “the difference between them and me is that I was given a chance to study this. I had access to people explaining how incredible and exciting physics is.”

König sees a stark disconnect between physics in Africa and physics everywhere else. She wants universities around the world to make connections with African universities, building efforts to encourage students of all backgrounds to pursue the field of physics.

König explains that ushering in more Black and African physicists means starting at the beginning and encouraging more undergraduates and young students to enter the field. “There is an enormous amount of talent and brilliance there,” König says. She sees an opportunity to connect with students across Africa, building the bridges needed to help everyone pursue the questions that keep them looking up at the stars.

While König loves her research, she knows theoretical cosmology has far to come to as a discipline. “There is so much room to grow in the field. It’s not all figured out.”


Mon, 27 Nov 2023 15:15:00 -0500

Celebrating five years of MIT.nano
Posted on Monday November 27, 2023

Category : Special events and guest speakers

Author : Amanda Stoll DiCristofaro | MIT.nano

The Nano Summit highlights nanoscale research across multiple disciplines at MIT.

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There is vast opportunity for nanoscale innovation to transform the world in positive ways — expressed MIT.nano Director Vladimir Bulović as he posed two questions to attendees at the start of the inaugural Nano Summit: “Where are we heading? And what is the next big thing we can develop?”

“The answer to that puts into perspective our main purpose — and that is to change the world,” Bulović, the Fariborz Maseeh Professor of Emerging Technologies, told an audience of more than 325 in-person and 150 virtual participants gathered for an exploration of nano-related research at MIT and a celebration of MIT.nano’s fifth anniversary.

Over a decade ago, MIT embarked on a massive project for the ultra-small — building an advanced facility to support research at the nanoscale. Construction of MIT.nano in the heart of MIT’s campus, a process compared to assembling a ship in a bottle, began in 2015, and the facility launched in October 2018.

Fast forward five years: MIT.nano now contains nearly 170 tools and instruments serving more than 1,200 trained researchers. These individuals come from over 300 principal investigator labs, representing more than 50 MIT departments, labs, and centers. The facility also serves external users from industry, other academic institutions, and over 130 startup and multinational companies.

A cross section of these faculty and researchers joined industry partners and MIT community members to kick off the first Nano Summit, which is expected to become an annual flagship event for MIT.nano and its industry consortium. Held on Oct. 24, the inaugural conference was co-hosted by the MIT Industrial Liaison Program.

Six topical sessions highlighted recent developments in quantum science and engineering, materials, advanced electronics, energy, biology, and immersive data technology. The Nano Summit also featured startup ventures and an art exhibition.

Watch the videos here.

Seeing and manipulating at the nanoscale — and beyond

“We need to develop new ways of building the next generation of materials,” said Frances Ross, the TDK Professor in Materials Science and Engineering (DMSE). “We need to use electron microscopy to help us understand not only what the structure is after it’s built, but how it came to be. I think the next few years in this piece of the nano realm are going to be really amazing.”

Speakers in the session “The Next Materials Revolution,” chaired by MIT.nano co-director for Characterization.nano and associate professor in DMSE James LeBeau, highlighted areas in which cutting-edge microscopy provides insights into the behavior of functional materials at the nanoscale, from anti-ferroelectrics to thin-film photovoltaics and 2D materials. They shared images and videos collected using the instruments in MIT.nano’s characterization suites, which were specifically designed and constructed to minimize mechanical-vibrational and electro-magnetic interference.

Later, in the “Biology and Human Health” session chaired by Boris Magasanik Professor of Biology Thomas Schwartz, biologists echoed the materials scientists, stressing the importance of the ultra-quiet, low-vibration environment in Characterization.nano to obtain high-resolution images of biological structures.

“Why is MIT.nano important for us?” asked Schwartz. “An important element of biology is to understand the structure of biology macromolecules. We want to get to an atomic resolution of these structures. CryoEM (cryo-electron microscopy) is an excellent method for this. In order to enable the resolution revolution, we had to get these instruments to MIT. For that, MIT.nano was fantastic.”

Seychelle Vos, the Robert A. Swanson (1969) Career Development Professor of Life Sciences, shared CryoEM images from her lab’s work, followed by biology Associate Professor Joey Davis who spoke about image processing. When asked about the next stage for CryoEM, Davis said he’s most excited about in-situ tomography, noting that there are new instruments being designed that will improve the current labor-intensive process.

To chart the future of energy, chemistry associate professor Yogi Surendranath is also using MIT.nano to see what is happening at the nanoscale in his research to use renewable electricity to change carbon dioxide into fuel.

“MIT.nano has played an immense role, not only in facilitating our ability to make nanostructures, but also to understand nanostructures through advanced imaging capabilities,” said Surendranath. “I see a lot of the future of MIT.nano around the question of how nanostructures evolve and change under the conditions that are relevant to their function. The tools at MIT.nano can help us sort that out.”

Tech transfer and quantum computing

The “Advanced Electronics” session chaired by Jesús del Alamo, the Donner Professor of Science in the Department of Electrical Engineering and Computer Science (EECS), brought together industry partners and MIT faculty for a panel discussion on the future of semiconductors and microelectronics. “Excellence in innovation is not enough, we also need to be excellent in transferring these to the marketplace,” said del Alamo. On this point, panelists spoke about strengthening the industry-university connection, as well as the importance of collaborative research environments and of access to advanced facilities, such as MIT.nano, for these environments to thrive.

The session came on the heels of a startup exhibit in which eleven START.nano companies presented their technologies in health, energy, climate, and virtual reality, among other topics. START.nano, MIT.nano’s hard-tech accelerator, provides participants use of MIT.nano’s facilities at a discounted rate and access to MIT’s startup ecosystem. The program aims to ease hard-tech startups’ transition from the lab to the marketplace, surviving common “valleys of death” as they move from idea to prototype to scaling up.

When asked about the state of quantum computing in the “Quantum Science and Engineering” session, physics professor Aram Harrow related his response to these startup challenges. “There are quite a few valleys to cross — there are the technical valleys, and then also the commercial valleys.” He spoke about scaling superconducting qubits and qubits made of suspended trapped ions, and the need for more scalable architectures, which we have the ingredients for, he said, but putting everything together is quite challenging.

Throughout the session, William Oliver, professor of physics and the Henry Ellis Warren (1894) Professor of Electrical Engineering and Computer Science, asked the panelists how MIT.nano can address challenges in assembly and scalability in quantum science.

“To harness the power of students to innovate, you really need to allow them to get their hands dirty, try new things, try all their crazy ideas, before this goes into a foundry-level process,” responded Kevin O’Brien, associate professor in EECS. “That’s what my group has been working on at MIT.nano, building these superconducting quantum processors using the state-of-the art fabrication techniques in MIT.nano.”

Connecting the digital to the physical

In his reflections on the semiconductor industry, Douglas Carlson, senior vice president for technology at MACOM, stressed connecting the digital world to real-world application. Later, in the “Immersive Data Technology” session, MIT.nano associate director Brian Anthony explained how, at the MIT.nano Immersion Lab, researchers are doing just that.

“We think about and facilitate work that has the human immersed between hardware, data, and experience,” said Anthony, principal research scientist in mechanical engineering. He spoke about using the capabilities of the Immersion Lab to apply immersive technologies to different areas — health, sports, performance, manufacturing, and education, among others. Speakers in this session gave specific examples in hardware, pediatric health, and opera.

Anthony connected this third pillar of MIT.nano to the fab and characterization facilities, highlighting how the Immersion Lab supports work conducted in other parts of the building. The Immersion Lab’s strength, he said, is taking novel work being developed inside MIT.nano and bringing it up to the human scale to think about applications and uses.

Artworks that are scientifically inspired

The Nano Summit closed with a reception at MIT.nano where guests could explore the facility and gaze through the cleanroom windows, where users were actively conducting research. Attendees were encouraged to visit an exhibition on MIT.nano’s first- and second-floor galleries featuring work by students from the MIT Program in Art, Culture, and Technology (ACT) who were invited to utilize MIT.nano’s tool sets and environments as inspiration for art.

In his closing remarks, Bulović reflected on the community of people who keep MIT.nano running and who are using the tools to advance their research. “Today we are celebrating the facility and all the work that has been done over the last five years to bring it to where it is today. It is there to function not just as a space, but as an essential part of MIT’s mission in research, innovation, and education. I hope that all of us here today take away a deep appreciation and admiration for those who are leading the journey into the nano age.”


Mon, 27 Nov 2023 11:45:00 -0500

Richard Fletcher named a 2023 Packard Fellow
Posted on Monday November 27, 2023

Category : Awards, honors and fellowships

Author : Sandi Miller | Department of Physics

Atomic physicist recognized for working to create and study exciting types of quantum matter; two MIT alumni also named.

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The David and Lucile Packard Foundation has announced that atomic physicist Richard Fletcher, assistant professor of physics and a researcher at MIT-Harvard Center for Ultracold Atoms (CUA) and the MIT Research Laboratory of Electronics (RLE), has been named a 2023 Packard Fellow for Science and Engineering. The Packard Foundation Fellowships are one of the most prestigious and well-funded nongovernmental awards for early-career scientists.

Fletcher is one of 20 innovative early-career scientists and engineers named to the 2023 class of Packard Fellows for Science and Engineering. Two MIT alumni were also named: Ritchie Chen SM ’13, PhD ’16 and Yang Yang PhD ’16, both now at the University of California at San Francisco. Each fellow receives $875,000 over five years to pursue their research.

“It’s a tremendous honor to be awarded a Packard Fellowship, and I’m very grateful to the foundation for their support of our work,” says Fletcher. “It’s quite inspiring to look down the list of alumni, and I hope that we will live up to the same high standards.” 

Fletcher and his lab use precisely controlled gases of atoms at ultracold temperatures to create and study exciting types of quantum matter. He uses atomic vapors, which are a million times thinner than air and a million times colder than interstellar space, which in turn are manipulated by laser beams and magnetic fields, he says.

“In many systems in nature, the behavior of many particles is qualitatively different to the underlying single-particle physics,” he explains. “For example, superconductivity is the frictionless flow of electrical current, which occurs in many low-temperature materials, but you can’t understand it from the physics of a single electron. In turns out that in general, describing the emergence of macroscopic phenomena from microscopic ingredients is really hard once the rule book is quantum mechanical.

“We approach this problem by building little tailor-made quantum worlds, formed by very cold gases of atoms, a million times colder than deep space, controlled and manipulated by laser beams and magnetic fields. In particular, since these platforms are free from many of the constraints imposed by real materials, we can use them to create states of matter that nature has simply never allowed to exist before. And honestly, some of the time we just use these exquisite tools we’ve developed to simply play around and have fun in the lab, and see what surprises experiments throw our way. That’s what I love most about experimental science!”

A native of Chester, U.K., he earned his undergraduate degree in 2010 and his PhD in 2015 from Cambridge University, and in between those degrees he was a Frank Knox Fellow at Harvard University. His thesis focused on the interplay of superfluidity and Bose-Einstein condensation in two dimensions. In 2016, he arrived at MIT as a Pappalardo Fellow, working with Martin Zwierlein on quantum fluids in artificial magnetic fields, and joined the MIT faculty in 2020. In 2022 he was awarded the AFOSR Young Investigator Award.

Past Packard fellows have gone on to receive such honors as the Nobel Prize in chemistry and physics, the Fields Medal, Alan T. Waterman Awards, Breakthrough Prizes, Kavli Prizes, and elections to the national academies of Science, Engineering, and Medicine.

Each year, the foundation invites 50 universities to nominate two faculty members for consideration. The Packard Fellowships Advisory Panel, a group of 12 internationally recognized scientists and engineers, evaluates the nominations and recommends fellows for approval by the Packard Foundation Board of Trustees. The Packard Foundation also continues to support fellows as they undertake a variety of self-directed initiatives to support diversity, equity, and inclusion in STEM through additional targeted grants.


Mon, 20 Nov 2023 13:40:00 -0500

Three MIT affiliates receive Schmidt awards
Posted on Monday November 20, 2023

Category : Awards, honors and fellowships

Author : Sandi Miller | Department of Mathematics

Jörn Dunkel and Surya Ganguli ’98, MNG ’98 receive Science Polymath awards; Josh Tenenbaum is named AI2050 Senior Fellow.

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Two MIT faculty were recently honored by Schmidt Futures, a philanthropic initiative of Eric and Wendy Schmidt. MathWorks Professor Jörn Dunkel received the 2023 Schmidt Science Polymath award, and professor of computational cognitive science Josh Tenenbaum was named a Schmidt Futures AI2050 Senior Fellow.

Also winning a Schmidt Science Polymath award was Surya Ganguli ’98, MNG ’98, who is an associate professor at Stanford University.

Science Polymaths

Dunkel is part of a select group of nine distinguished scientists who this year join the existing network of Schmidt Science Polymaths, awarded to recently tenured professors with remarkable track records doing interdisciplinary research.

The Schmidt Futures Initiative awards $500,000 per year for up to five years to support innovative, highly interdisciplinary research by recently tenured professors with remarkable track records, promising futures, and a desire to explore interdisciplinary research.

Dunkel’s current research studies self-organization processes in complex biological and physical systems across a wide range of scales, from bacterial biofilms and embryonic tissues to brain dynamics and global trade networks. In collaboration with their experimental partner labs at MIT, his group is developing and investigating mathematical models that describe and predict the emergent dynamical behaviors of multicellular and multi-organismal communities. By analyzing the structure of the underlying model equations, Dunkel seeks ways to bridge seemingly disparate systems through the “common language” of math.

“I would like to express my profound thanks to the Schmidt Futures Initiative for this generous award, which gives us the freedom to explore new research directions,” says Dunkel. “I am particularly grateful for the encouragement to pursue interdisciplinary projects that aim to challenge prevalent paradigms by integrating state-of-the-art data acquisition with new mathematical approaches. And a big thank you to my PhD students and postdocs and our collaborators whose exceptional work is recognized through this award.”

Surya Ganguli was a triple undergraduate MIT major in electrical engineering and computer science, physics, and mathematics. Now as an associate professor of applied physics at Stanford, he leads the Neural Dynamics and Computation Lab and has been a visiting researcher at both Google and Meta AI. His research spans the fields of neuroscience, machine learning, and physics, focusing on understanding and improving how both biological and artificial neural networks learn striking emergent computations.

AI2050 Senior Fellow

Josh Tenenbaum, a professor in the Department of Brain and Cognitive Sciences who pursues research in computational cognitive science, was selected as a 2023 Schmidt Futures AI2050 Senior Fellow. He holds appointments in the Computer Science and Artificial Intelligence Laboratory (CSAIL) and the Center for Brains, Minds, and Machines (CBMM), and serves as Director of Science for the MIT Quest for Intelligence.

Tenenbaum will pursue interdisciplinary research in artificial intelligence to help chart the development of AI for societal benefit. As a senior fellow, Tenenbaum’s long-term goal is to reverse-engineer intelligence in the human mind and brain, and use these insights to engineer more human-like machine intelligence.

AI2050 has allocated up to $7 million to support the new Senior Fellows’ research to address “hard problems” in AI in their respective fields including computer science, chemistry, cognitive science, the arts, and philosophy.

Tenenbaum is best known for theories of cognition as Bayesian inference, with a focus on explaining how humans can learn so much so quickly, from so little data. In AI, he has developed influential approaches to dimensionality reduction, unsupervised learning and structure discovery, and probabilistic programming.

His current research focuses on probabilistic program models of common sense in humans and machines, grounding language and perception in these representations, and learning based on program synthesis.


Thu, 16 Nov 2023 14:00:00 -0500

How cell identity is preserved when cells divide
Posted on Thursday November 16, 2023

Category : Research

Author : Anne Trafton | MIT News

MIT study suggests 3D folding of the genome is key to cells’ ability to store and pass on “memories” of which genes they should express.

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Every cell in the human body contains the same genetic instructions, encoded in its DNA. However, out of about 30,000 genes, each cell expresses only those genes that it needs to become a nerve cell, immune cell, or any of the other hundreds of cell types in the body.

Each cell’s fate is largely determined by chemical modifications to the proteins that decorate its DNA; these modification in turn control which genes get turned on or off. When cells copy their DNA to divide, however, they lose half of these modifications, leaving the question: How do cells maintain the memory of what kind of cell they are supposed to be?

A new MIT study proposes a theoretical model that helps explain how these memories are passed from generation to generation when cells divide. The research team suggests that within each cell’s nucleus, the 3D folding of its genome determines which parts of the genome will be marked by these chemical modifications. After a cell copies its DNA, the marks are partially lost, but the 3D folding allows the cell to easily restore the chemical marks needed to maintain its identity. And each time a cell divides, chemical marks allow a cell to restore its 3D folding of its genome. This way, by juggling the memory between 3D folding and the marks, the memory can be preserved over hundreds of cell divisions.

“A key aspect of how cell types differ is that different genes are turned on or off. It's very difficult to transform one cell type to another because these states are very committed,” says Jeremy Owen PhD ’22, the lead author of the study. “What we have done in this work is develop a simple model that highlights qualitative features of the chemical systems inside cells and how they need to work in order to make memories of gene expression stable.”

Leonid Mirny, a professor in MIT’s Institute for Medical Engineering and Science and the Department of Physics, is the senior author of the paper, which appears today in Science. Dino Osmanović, a former postdoctoral fellow at MIT’s Center for the Physics of Living Systems, is also an author of the study.

Maintaining memory

Within the cell nucleus, DNA is wrapped around proteins called histones, forming a densely packed structure known as chromatin. Histones can display a variety of modifications that help control which genes are expressed in a given cell. These modifications generate “epigenetic memory,” which helps a cell to maintain its cell type. However, how this memory is passed on to daughter cells is somewhat of a mystery.

Previous work by Mirny’s lab has shown that the 3D structure of chromosomes is, to a great extent, determined by these epigenetic modifications, or marks. In particular, they found that certain chromatin regions, with marks telling cells not to read a particular segment of DNA, attract each other and form dense clumps called heterochromatin, which are difficult for the cell to access.

In their new study, Mirny and his colleagues wanted to answer the question of how those epigenetic marks are maintained from generation to generation. They developed a computational model of a polymer with a few marked regions, and saw that these marked regions collapse into each other, forming a dense clump. Then they studied how these marks are lost and gained.

When a cell copies its DNA to divide it between two daughter cells, each copy gets about half of the epigenetic marks. The cell then needs to restore the lost marks before the DNA is passed to the daughter cells, and the way chromosomes were folded serves as a blueprint for where these remaining marks should go.

These modifications are added by specialized enzymes known as “reader-writer” enzymes. Each of these enzymes is specific for a certain mark, and once they “read” existing marks, they “write” additional marks at nearby locations. If the chromatin is already folded into a 3D shape, marks will accumulate in regions that already had modifications inherited from the parent cell.

“There are several lines of evidence that suggest that the spreading can happen in 3D, meaning if there are two parts that are near each other in space, even if they're not adjacent along the DNA, then spreading can happen from one to another,” Owen says. “That is how the 3D structure can influence the spreading of these marks.”

This process is analogous to the spread of infectious disease, as the more contacts that a chromatin region has with other regions, the more likely it is to be modified, just as an individual is more likely to become infected as their number of contacts increases. In this analogy, dense regions of marked chromatin are like cities where people have many social interactions, while the rest of the genome is comparable to sparsely populated rural areas.

“That essentially means that the marks will be spreading in the dense region and will be very sparse anywhere outside it,” Mirny says.

The new model also suggests possible parallels between epigenetic memories stored in a folded polymer and memories stored in a neural network, he adds. Folding of marked regions can be thought of as analogous to the strong connections formed between neurons that fire together in a neural network.

“Broadly this suggests that akin to the way neural networks are able to do very complex information processing, the epigenetic memory mechanism we described may be able to process information, not only store it,” he says.

“One beautiful aspect of the work is how it offers and explores connections with ideas from the seemingly very distant corners of science, including spreading of infections (to describe formation of new chemical marks in the 3D vicinity of the existing one), associative memory in model neural networks, and protein folding,” says Alexander Grosberg, a professor of physics at New York University, who was not involved in the research.

Epigenetic erosion

While this model appeared to offer a good explanation for how epigenetic memory can be maintained, the researchers found that eventually, reader-writer enzyme activity would lead to the entire genome being covered in epigenetic modifications. When they altered the model to make the enzyme weaker, it didn’t cover enough of the genome and memories were lost in a few cell generations.

To get the model to more accurately account for the preservation of epigenetic marks, the researchers added another element: limiting the amount of reader-writer enzyme available. They found that if the amount of enzyme was kept between 0.1 and 1 percent of the number of histones (a percentage based on estimates of the actual abundance of these enzymes), their model cells could accurately maintain their epigenetic memory for up to hundreds of generations, depending on the complexity of the epigenetic pattern.

It is already known that cells begin to lose their epigenetic memory as they age, and the researchers now plan to study whether the process they described in this paper might play a role in epigenetic erosion and loss of cell identity. They also plan to model a disease called progeria, in which cells have a genetic mutation that leads to loss of heterochromatin. People with this disease experience accelerated aging.

“The mechanistic link between these mutations and the epigenetic changes that eventually happen is not well understood,” Owen says. “It would be great to use a model like ours where there are dynamic marks, together with polymer dynamics, to try and explain that.”

The researchers also hope to work with collaborators to experimentally test some of the predictions of their model, which could be done, for example, by altering the level of reader-writer enzymes in living cells and measuring the effect on epigenetic memory.

The research was funded by the National Human Genome Research Institute, the National Institute of General Medical Sciences, and the National Science Foundation.


Thu, 16 Nov 2023 12:15:00 -0500

Five MIT affiliates receive awards from the American Physical Society
Posted on Thursday November 16, 2023

Category : Awards, honors and fellowships

Author : Sandi Miller | Department of Physics

Professor Wit Busza, Instructor Karol Bacik, postdocs Cari Cesarotti and Chao Li, and Pablo Gaston Debenedetti SM ’81, PhD ’85 honored for contributions to physics.

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The American Physical Society (APS) recently honored five MIT community members for their contributions to physics: Professor Wit Busza, Instructor Karol Bacik, postdocs Cari Cesarotti and Chao Li, and Pablo Gaston Debenedetti SM ’81, PhD ’85.

Tom W. Bonner Prize in Nuclear Physics

Wit Busza, the Francis L. Friedman Professor of Physics Emeritus, and a researcher in the Laboratory for Nuclear Science, was awarded the Tom W. Bonner Prize in Nuclear Physics “for pioneering work on multi-particle production in proton-nucleus and nucleus-nucleus collisions, including the discovery of participant scaling, and for the conception and leadership of the PHOBOS experiment.”

The prize recognizes outstanding experimental research in nuclear physics, including the development of a method, technique, or device that significantly contributes to nuclear physics research.

When two protons or nuclei traveling at close to the speed of light collide, a vast number of particles are created. It is a distinct example of energy converting to mass. As an example, when lead nuclei collide in the highest-energy colliders, one often sees over 10,000 protons, neutrons, antiprotons, pi-mesons, etc. streaming out from the tiny volume where the collision took place.

“It's amazing if you consider that this volume is no larger than that of a mere 100 or so of such particles,” Busza says. “The question arises: What exactly is this extremely hot (more than a billion times higher temperature than the surface of the sun) and super dense stuff, which was produced in the collision, before it evolved into the observed large number of created particles? It is a particularly interesting question since we think it is the same stuff, named the quark-gluon plasma, out of which most of our universe was made at about 10 microseconds after the Big Bang.”

Busza is best known for influential pA experiments at Fermilab, in which he discovered participant scaling and obtained, together with Alfred Goldhaber, the first data-based estimate of the energy density that will be produced in the future Relativistic Heavy Ion Collider (RHIC). He’s also known for originating and leading the PHOBOS experiment, which together with the other RHIC experiments discovered a strongly interacting quantum chromodynamics liquid (at the time named “strongly interacting Quark-Gluon Plasma”).

Andreas Acrivos Dissertation Award in Fluid Dynamics

Instructor of applied mathematics Karol Bacik received the American Physical Society’s 2023 Andreas Acrivos Dissertation Award in Fluid Dynamics “for an elegant study of dune-dune repulsion and dune-obstacle interaction using laboratory experiments, data analysis, and mathematical modeling, elucidating the intricate feedback between sediment dynamics and fluid mechanics.”

His groundbreaking experimental and theoretical work on the dynamics of underwater sand dunes was done at the University of Cambridge, where he received his PhD in 2021. From 2021-23 Bacik was a research associate at the University of Bath, where he investigated a range of problems in active flows and mathematical biology. 

Bacik’s award lecture will be at the 76th Annual Meeting of the APS Division of Fluid Dynamics on Nov. 21.

J.J. and Noriko Sakurai Dissertation Award in Theoretical Particle Physics

Cari Cesarotti, a postdoc at the Center for Theoretical Physics, received the 2023 J.J. and Noriko Sakurai Dissertation Award in Theoretical Particle Physics “for exploration of collider signals of physics beyond the Standard Model, including the development and assessment of a novel collider event-shape observable tailored for distinguishing strongly coupled hidden sectors from background, and studies of physics at future muon accelerators and colliders.”

Cesarotti’s research program works toward discovering physics beyond the Standard Model in robust ways. This includes developing novel observables, model-building new physics scenarios, and advancing the physics case for future experiments. She is also an active member of the muon collider community. Cesarotti completed her BA in physics at Cornell University in 2017, and completed her dissertation in high-energy particle theory under Professor Matthew Reece at Harvard University in 2022.

Outstanding Doctoral Thesis Research in Beam Physics Award

Research Laboratory of Electronics (RLE) postdoc Chao Li received the 2023 Outstanding Doctoral Thesis Research in Beam Physics Award “for seminal and highly creative contributions to the development of microfabricated, miniature atomic beam technology and the invention of new chip-scale techniques that enable precise and targeted delivery of neutral atoms.”

With MIT RLE’s Quantum Photonics and AI Group, Li is exploring the use of large-scale photonic integrated circuits for the fast and coherent control of various types of qubits, such as color centers in diamonds, trapped neutral atoms, and ions. Li earned his bachelor’s degree from Jilin University in 2016, and his PhD from Georgia Tech in 2022, both in physics.

Aneesur Rahman Prize for Computational Physics

Pablo Gaston Debenedetti SM ’81, PhD ’85, an alumnus of the MIT Department of Chemical Engineering who is currently the Princeton University dean for research, received the 2023 Aneesur Rahman Prize for Computational Physics “for seminal contributions to the science of supercooled liquids and glasses, water, and aqueous solutions, through ground-breaking simulations.”

Debenedetti’s research interests include supercooled water, glasses, protein thermodynamics, nucleation, metastability, the origin of biological homochirality, and hydrophobicity. His most important results, obtained with students and collaborators, include providing rigorous computational proof of the existence of a liquid-liquid transition in several water models, and demonstrating the relationship between structural order and water’s anomalies.


Tue, 14 Nov 2023 15:10:00 -0500

MIT physicists turn pencil lead into “gold”
Posted on Tuesday November 14, 2023

Category : Research

Author : Elizabeth A. Thomson | Materials Research Laboratory

Thin flakes of graphite can be tuned to exhibit three important properties.

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MIT physicists have metaphorically turned graphite, or pencil lead, into gold by isolating five ultrathin flakes stacked in a specific order. The resulting material can then be tuned to exhibit three important properties never before seen in natural graphite.

“It is kind of like one-stop shopping,” says Long Ju, an assistant professor in the Department of Physics and leader of the work, which is reported in the Oct. 5 issue of Nature Nanotechnology. “Nature has plenty of surprises. In this case, we never realized that all of these interesting things are embedded in graphite.”

Further, he says, “It is very rare material to find materials that can host this many properties.”

Graphite is composed of graphene, which is a single layer of carbon atoms arranged in hexagons resembling a honeycomb structure. Graphene, in turn, has been the focus of intense research since it was first isolated about 20 years ago. More recently, about five years ago, researchers including a team at MIT discovered that stacking individual sheets of graphene, and twisting them at a slight angle to each other, can impart new properties to the material, from superconductivity to magnetism. The field of “twistronics” was born.

In the current work, “we discovered interesting properties with no twisting at all,” says Ju, who is also affiliated with the Materials Research Laboratory.

He and colleagues discovered that five layers of graphene arranged in a certain order allow the electrons moving around inside the material to talk with each other. That phenomenon, known as electron correlation, “is the magic that makes all of these new properties possible,” Ju says.

Bulk graphite — and even single sheets of graphene — are good electrical conductors, but that’s it. The material Ju and colleagues isolated, which they call pentalayer rhombohedral stacked graphene, becomes much more than the sum of its parts.

Novel microscope

Key to isolating the material was a novel microscope Ju built at MIT in 2021 that can quickly and relatively inexpensively determine a variety of important characteristics of a material at the nanoscale. Pentalayer rhombohedral stacked graphene is only a few billionths of a meter thick.

Scientists including Ju were looking for multilayer graphene that was stacked in a very precise order, known as rhombohedral stacking. Says Ju, “there are more than 10 possible stacking orders when you go to five layers. Rhombohedral is just one of them.” The microscope Ju built, known as Scattering-type Scanning Nearfield Optical Microscopy, or s-SNOM, allowed the scientists to identify and isolate only the pentalayers in the rhombohedral stacking order they were interested in.

Three in one

From there, the team attached electrodes to a tiny sandwich composed of boron nitride “bread” that protects the delicate “meat” of pentalayer rhombohedral stacked graphene. The electrodes allowed them to tune the system with different voltages, or amounts of electricity. The result: They discovered the emergence of three different phenomena depending on the number of electrons flooding the system.

“We found that the material could be insulating, magnetic, or topological,” Ju says. The latter is somewhat related to both conductors and insulators. Essentially, Ju explains, a topological material allows the unimpeded movement of electrons around the edges of a material, but not through the middle. The electrons are traveling in one direction along a “highway” at the edge of the material separated by a median that makes up the center of the material. So the edge of a topological material is a perfect conductor, while the center is an insulator.

“Our work establishes rhombohedral stacked multilayer graphene as a highly tunable platform to study these new possibilities of strongly correlated and topological physics,” Ju and his coauthors conclude in Nature Nanotechnology.

In addition to Ju, authors of the paper are Tonghang Han and Zhengguang Lu. Han is a graduate student in the Department of Physics; Lu is a postdoc in the Materials Research Laboratory. The two are co-first authors of the paper.

Other authors are Giovanni Scuri, Jiho Sung, Jue Wang and Hongkun Park of Harvard University; Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan; and Tianyi Han of the MIT Department of Physics.

This work was supported by a Sloan Fellowship; the U.S. National Science Foundation; the U.S. Office of the Under Secretary of Defense for Research and Engineering; the Japan Society for the Promotion of Science KAKENHI;  the World Premier International Research Initiative of Japan; and the U.S. Air Force Office of Scientific Research.


Wed, 08 Nov 2023 11:00:00 -0500

Physicists trap electrons in a 3D crystal for the first time
Posted on Wednesday November 08, 2023

Category : Electronics

Author : Jennifer Chu | MIT News

The results open the door to exploring superconductivity and other exotic electronic states in three-dimensional materials.

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Electrons move through a conducting material like commuters at the height of Manhattan rush hour. The charged particles may jostle and bump against each other, but for the most part they’re unconcerned with other electrons as they hurtle forward, each with their own energy.

But when a material’s electrons are trapped together, they can settle into the exact same energy state and start to behave as one. This collective, zombie-like state is what’s known in physics as an electronic “flat band,” and scientists predict that when electrons are in this state they can start to feel the quantum effects of other electrons and act in coordinated, quantum ways. Then, exotic behavior such as superconductivity and unique forms of magnetism may emerge.

Now, physicists at MIT have successfully trapped electrons in a pure crystal. It is the first time that scientists have achieved an electronic flat band in a three-dimensional material. With some chemical manipulation, the researchers also showed they could transform the crystal into a superconductor — a material that conducts electricity with zero resistance.

The electrons’ trapped state is possible thanks to the crystal’s atomic geometry. The crystal, which the physicists synthesized, has an arrangement of atoms that resembles the woven patterns in “kagome,” the Japanese art of basket-weaving. In this specific geometry, the researchers found that rather than jumping between atoms, electrons were “caged,” and settled into the same band of energy.

Animation of spinning 3D crystal structure that looks like a star made up of latticed cubes and pyramids.

The researchers say that this flat-band state can be realized with virtually any combination of atoms — as long as they are arranged in this kagome-inspired 3D geometry. The results, appearing today in Nature, provide a new way for scientists to explore rare electronic states in three-dimensional materials. These materials might someday be optimized to enable ultraefficient power lines, supercomputing quantum bits, and faster, smarter electronic devices.

“Now that we know we can make a flat band from this geometry, we have a big motivation to study other structures that might have other new physics that could be a platform for new technologies,” says study author Joseph Checkelsky, associate professor of physics.

Checkelsky’s MIT co-authors include graduate students Joshua Wakefield, Mingu Kang, and Paul Neves, and postdoc Dongjin Oh, who are co-lead authors; graduate students Tej Lamichhane and Alan Chen; postdocs Shiang Fang and Frank Zhao; undergraduate Ryan Tigue; associate professor of nuclear science and engineering Mingda Li; and associate professor of physics Riccardo Comin, who collaborated with Checkelsky to direct the study; along with collaborators at multiple other laboratories and institutions.

Setting a 3D trap

In recent years, physicists have successfully trapped electrons and confirmed their electronic flat-band state in two-dimensional materials. But scientists have found that electrons that are trapped in two dimensions can easily escape out the third, making flat-band states difficult to maintain in 2D.

In their new study, Checkelsky, Comin, and their colleagues looked to realize flat bands in 3D materials, such that electrons would be trapped in all three dimensions and any exotic electronic states could be more stably maintained. They had an idea that kagome patterns might play a role.

In previous work, the team observed trapped electrons in a two-dimensional lattice of atoms that resembled some kagome designs. When the atoms were arranged in a pattern of interconnected, corner-sharing triangles, electrons were confined within the hexagonal space between triangles, rather than hopping across the lattice. But, like others, the researchers found that the electrons could escape up and out of the lattice, through the third dimension.

The team wondered: Could a 3D configuration of similar lattices work to box in the electrons? They looked for an answer in databases of material structures and came across a certain geometric configuration of atoms, classified generally as a pyrochlore — a type of mineral with a highly symmetric atomic geometry. The pychlore’s 3D structure of atoms formed a repeating pattern of cubes, the face of each cube resembling a kagome-like lattice. They found that, in theory, this geometry could effectively trap electrons within each cube.

Rocky landings

To test this hypothesis, the researchers synthesized a pyrochlore crystal in the lab.

“It’s not dissimilar to how nature makes crystals,” Checkelsky explains. “We put certain elements together — in this case, calcium and nickel — melt them at very high temperatures, cool them down, and the atoms on their own will arrange into this crystalline, kagome-like configuration.”

They then looked to measure the energy of individual electrons in the crystal, to see if they indeed fell into the same flat band of energy. To do so, researchers typically carry out photoemission experiments, in which they shine a single photon of light onto a sample, that in turn kicks out a single electron. A detector can then precisely measure the energy of that individual electron.

Scientists have used photoemission to confirm flat-band states in various 2D materials. Because of their physically flat, two-dimensional nature, these materials are relatively straightforward to measure using standard laser light. But for 3D materials, the task is more challenging.

“For this experiment, you typically require a very flat surface,” Comin explains. “But if you look at the surface of these 3D materials, they are like the Rocky Mountains, with a very corrugated landscape. Experiments on these materials are very challenging, and that is part of the reason no one has demonstrated that they host trapped electrons.”

The team cleared this hurdle with angle-resolved photoemission spectroscopy (ARPES), an ultrafocused beam of light that is able to target specific locations across an uneven 3D surface and measure the individual electron energies at those locations.

“It’s like landing a helicopter on very small pads, all across this rocky landscape,” Comin says.

With ARPES, the team measured the energies of thousands of electrons across a synthesized crystal sample in about half an hour. They found that, overwhelmingly, the electrons in the crystal exhibited the exact same energy, confirming the 3D material’s flat-band state.

To see whether they could manipulate the coordinated electrons into some exotic electronic state, the researchers synthesized the same crystal geometry, this time with atoms of rhodium and ruthenium instead of nickel. On paper, the researchers calculated that this chemical swap should shift the electrons’ flat band to zero energy — a state that automatically leads to superconductivity.

And indeed, they found that when they synthesized a new crystal, with a slightly different combination of elements, in the same kagome-like 3D geometry, the crystal’s electrons exhibited a flat band, this time at superconducting states.

“This presents a new paradigm to think about how to find new and interesting quantum materials,” Comin says. “We showed that, with this special ingredient of this atomic arrangement that can trap electrons, we always find these flat bands. It’s not just a lucky strike. From this point on, the challenge is to optimize to achieve the promise of flat-band materials, potentially to sustain superconductivity at higher temperatures.”


Tue, 07 Nov 2023 13:20:00 -0500

Three from MIT named American Physical Society Fellows for 2023
Posted on Tuesday November 07, 2023

Category : Awards, honors and fellowships

Author : School of Engineering

APS honors Paola Cappellaro, Maria Gatu Johnson, and Bradley Olsen for research, applications, teaching, and leadership; 10 additional MIT alumni also honored.

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Three MIT researchers have been elected fellows of the American Physical Society (APS) for 2023. The APS Fellowship Program was created in 1921 for those in the physics community to recognize peers who have contributed to advances in physics through original research, innovative applications, teaching, and leadership. According to the APS, each year no more than one-half of 1 percent of the APS membership, excluding student members, are recognized by their peers for election to the status of fellow.

The following members of the MIT community were elected APS Fellows in 2023:

Paola Cappellaro, the Ford Professor of Engineering in the Department of Nuclear Science and Engineering, professor of physics, and member of the Research Laboratory of Electronics, is an expert in magnetic resonance, coherent control, and quantum information science. Cappellaro’s area of inquiry focuses on spin-based quantum information processing and precision measurements. With collaborators, she developed the concept and first demonstrations of NV-diamond magnetometers. Cappellaro’s major contributions have been in developing control techniques for nuclear and electronic spin qubits. Her work not only provides a deeper understanding of quantum many-body systems and their environment, but also applies this knowledge to the development of practical quantum nano-devices, such as sensors and simulators. The APS Division of Atomic, Molecular and Optical Physics elected Cappellaro for groundbreaking contributions to quantum control and quantum sensing with spin systems.

Maria Gatu Johnson, principal research scientist at the Plasma Science and Fusion Center, studies thermonuclear fusion generated by a process called inertial confinement, where lasers are used to implode a spherical capsule containing the fuel to high densities and temperatures. Gatu Johnson is particularly interested in understanding the conditions that influence the amount of energy generated by the thermonuclear fusion process, and she has developed unique diagnostic tools that allow for very precise analysis of the fusion experiments. The APS Division of Plasma Physics elected Gatu Johnson for pioneering efforts in the cross-cut field of plasma-nuclear science and for groundbreaking studies of macroscopic plasma flows in inertial confinement fusion implosions.

Bradley Olsen, the Alexander and I. Michael Kasser (1960) Professor in the Department of Chemical Engineering, is the faculty director of the MIT-Brazil and MIT-Amazonia programs in MIT’s Center for International Studies and a member of the Program in Polymers and Soft Matter. His research within the physics community specializes in polymer physics, touching on areas including the physics of biomolecules, self-assembly, network physics, and polymer informatics. He is particularly interested in how biosynthesis can be used as a natural green chemistry for the preparation of designer polymeric materials, how controlled polymerization through biology can give us unique materials that provide insight into polymer physics, and the unique physics of self-assembly in complex protein nanostructures for biotechnology and energy applications. He was awarded the APS Dillon Medal for Polymer Physics in 2016. The APS Division of Polymer Physics elected Olsen for developing new theories of polymer gel mechanics that account for network topology, and for generating applied theory and experiments to advance our understanding of polymer self-assembly and dynamics using proteins and hybrid protein macromolecules as model polymer systems.

Ten additional alumni were also elected to the APS this year. They are: Reba M. Bandyopadhyay ’93; David L. Hu ’01, PhD ’06; Kerwyn Casey Huang PhD ’04; H. Pirouz Kavehpour PhD ’03; Boris Kozinsky ’00, PhD ’07; Manyalibo J. Matthews PhD ’98; Felix I. Parra SM ’07, PhD ’09; Dmitry A. Pushin PhD ’07; Caterina Riconda PhD ’97; and Sarah Veatch ’98.


Wed, 01 Nov 2023 17:00:00 -0400

The power of representation and connectivity in STEM education
Posted on Wednesday November 01, 2023

Category : Special events and guest speakers

Author : Laboratory for Nuclear Science

Bridging Talents and Opportunities event serves as an outreach initiative for the Latin community.

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On Oct. 13 and 14 at the Wong Auditorium at MIT, an event called Bridging Talents and Opportunities took place. It was part of an initiative led by MIT Latinx professors and students aimed at providing talented Latinx high school students from the greater Boston area and various Latin American countries a unique chance to explore the world of science and innovation within MIT's campus.

The primary goal of the effort is to inspire and empower talented, low-income high school scholars, particularly those from first-generation and low-income backgrounds. These students are driven by the inspiring life stories of Latinx scientists who have overcome similar circumstances to make remarkable contributions to the field and who are now affiliated with some of the world's top universities.

The two-day gathering commenced with a roster of esteemed speakers who were scientists, academics, philanthropists, and trailblazing entrepreneurs, most of Hispanic and Latin American origin. They shared stories of success and their affiliation with prestigious institutions globally, and underscored the achievements and the heights to which one can rise with determination and support.

As part of the event, students, parents, and teachers had the opportunity to visit some science labs at MIT such the Laboratory for Nuclear Science (LNS)’s Laboratory of Exotics Molecules and Atoms, Laboratory for Atomic and Quantum Physics, and the Robotic Lab. With the support of the Harvard Colombian Student Society the group was also able to take a tour to the Harvard University campus.

Diana Grass, an organizer of Bridging Talents and Opportunities, is a second-year PhD student in medical engineering and medical physics in the Harvard-MIT Health Sciences and Technology program. She also serves as the co-founder and co-president of the Graduate First Generation Low-Income student group at MIT (GFLI@MIT).

"In countries like Colombia, it takes an astounding 11 generations, according to the OECD [Organization for Economic Co-operation and Development], to escape poverty," Grass emphasized. "Education is the most powerful tool to break this chain. As a first-generation student and a Latina, I have firsthand experience of the socioeconomic obstacles that hinder educational pursuits and degree attainment. Bold actions are needed if we are to address diversity, the gender gap, and equity within the realm of science. It's immensely gratifying that we can drive these actions forward from top universities like MIT.”

Grass added, “Latino students — especially women — have historically been underrepresented in STEM careers, underscoring the urgency of instilling early motivation in the educational journey. Creating opportunities for first-generation low-income students is an essential step in this direction. This initiative recognizes that addressing educational disparities requires proactive measures.”

The event also hosted Jeison Aristizabal, recognized as the 2016 CNN Hero of the Year and the founder of the first Latin American University for people with disabilities. Overcoming his own cerebral palsy, Aristizabal is now a social communicator and lawyer, redefining the concept of disability and serving as an inspiration to countless students with disabilities. Grass states, “His journey highlights the extraordinary achievements that can be realized through perseverance and determination.”

Edwin Pedrozo-Peñafiel, another event organizer, is a research scientist in the Research Laboratory of Electronics and MIT-Harvard Center for Ultracold Atoms. He stated that “Seeing such a dynamic group of accomplished individuals from similar cultural backgrounds made a compelling statement. It's essential that the younger generations see successful figures they can identify with. Representation in any field, but particularly in STEAM [science, technology, engineering, arts, and mathematics], is not just about checking a box. It's a potent source of inspiration. When young students can look up and see someone who looks like them, speaks like them, and shares a similar cultural narrative achieving greatness, it tells them one vital thing: ‘I can do it, too.’”

He continued, “Beyond individual success stories, the event spotlighted the importance of collective effort. By connecting diverse stakeholders around the shared goal of education, we can amplify the message of the value and transformative power of STEAM careers. Students should recognize that these fields aren't just viable career paths; they're avenues to impact their families, communities, and even the world positively.”

Boleslaw Wyslouch, professor of physics and director of the Laboratory for Nuclear Science and the Bates Research and Engineering Center, provided introductory comments in a welcome at the beginning of the Friday session. He said, “I was delighted that MIT and the Laboratory for Nuclear Science were able to help welcome Latino students from the Boston area, from around the country, and from abroad to the workshop. The combination of inspirational speakers, practical information, and visits to world-class MIT laboratories organized by Professor Ronald Garcia Ruiz was an excellent way to showcase the opportunities in science and engineering. I am very grateful to many outside organizations for sponsoring the students and their families to attend the event.”

Professor Garcia Ruiz, who is a researcher in LNS and one of the organizers, emphasized, “Disadvantaged youths, especially those from underserved communities, are disproportionately affected by the world's major challenges, including climate change, inequality, water scarcity, and food security, to name a few. However, these firsthand experiences also provide them with a unique perspective and motivation. When equipped with the right resources and education, these individuals do not merely thrive — they lead.

“By creating bonds between these talented young individuals, their families, committed educational foundations, global leaders from various fields, and visionary entrepreneurs and institutions, the event aimed to secure opportunities to empower them to become the innovators and transformative leaders of tomorrow. However, a stark reality persists. Often, even in the face of available opportunities, many of these young individuals do not take them — either due to lack of awareness, the pressure of their communities, or fear of venturing into the unknown. We are hopeful that our initiative will help bridge this gap.

“The wave of support from LNS, the MIT community, and from outside has been deeply heartening. The gratitude expressed by participants, especially by the students and their families, serves as our strongest motivation to continue with this mission.”


Mon, 23 Oct 2023 11:00:00 -0400

LIGO surpasses the quantum limit
Posted on Monday October 23, 2023

Category : Physics

Author : Whitney Clavin | MIT News

Researchers achieve a landmark in quantum squeezing.

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The following article is adapted from a press release issued by the Laser Interferometer Gravitational-wave Observatory (LIGO) Laboratory. LIGO is funded by the National Science Foundation and operated by Caltech and MIT, which conceived and built the project.

In 2015, the Laser Interferometer Gravitational-Wave Observatory, or LIGO, made history when it made the first direct detection of gravitational waves, or ripples in space and time, produced by a pair of colliding black holes. Since then, the U.S. National Science Foundation (NSF)-funded LIGO and its sister detector in Europe, Virgo, have detected gravitational waves from dozens of mergers between black holes as well as from collisions between a related class of stellar remnants called neutron stars. At the heart of LIGO’s success is its ability to measure the stretching and squeezing of the fabric of space-time on scales 10 thousand trillion times smaller than a human hair.

As incomprehensibly small as these measurements are, LIGO’s precision has continued to be limited by the laws of quantum physics. At very tiny, subatomic scales, empty space is filled with a faint crackling of quantum noise, which interferes with LIGO's measurements and restricts how sensitive the observatory can be. Now, writing in the journal Physical Review X, LIGO researchers report a significant advance in a quantum technology called “squeezing” that allows them to skirt around this limit and measure undulations in space-time across the entire range of gravitational frequencies detected by LIGO.

This new “frequency-dependent squeezing” technology, in operation at LIGO since it turned back on in May of this year, means that the detectors can now probe a larger volume of the universe and are expected to detect about 60 percent more mergers than before. This greatly boosts LIGO’s ability to study the exotic events that shake space and time.

“We can’t control nature, but we can control our detectors,” says Lisa Barsotti, a senior research scientist at MIT who oversaw the development of the new LIGO technology, a project that originally involved research experiments at MIT led by Matt Evans, professor of physics, and Nergis Mavalvala, the Curtis and Kathleen Marble Professor of Astrophysics and the dean of the School of Science. The effort now includes dozens of scientists and engineers based at MIT, Caltech, and the twin LIGO observatories in Hanford, Washington, and Livingston, Louisiana.

“A project of this scale requires multiple people, from facilities to engineering and optics — basically the full extent of the LIGO Lab with important contributions from the LIGO Scientific Collaboration. It was a grand effort made even more challenging by the pandemic,” Barsotti says.

“Now that we have surpassed this quantum limit, we can do a lot more astronomy,” explains Lee McCuller, assistant professor of physics at Caltech and one of the leaders of the new study. “LIGO uses lasers and large mirrors to make its observations, but we are working at a level of sensitivity that means the device is affected by the quantum realm.”

The results also have ramifications for future quantum technologies such as quantum computers and other microelectronics as well as for fundamental physics experiments. “We can take what we have learned from LIGO and apply it to problems that require measuring subatomic-scale distances with incredible accuracy,” McCuller says.

“When NSF first invested in building the twin LIGO detectors in the late 1990s, we were enthusiastic about the potential to observe gravitational waves,” says NSF Director Sethuraman Panchanathan. “Not only did these detectors make possible groundbreaking discoveries, they also unleashed the design and development of novel technologies. This is truly exemplar of the DNA of NSF — curiosity-driven explorations coupled with use-inspired innovations. Through decades of continuing investments and expansion of international partnerships, LIGO is further poised to advance rich discoveries and technological progress."

The laws of quantum physics dictate that particles, including photons, will randomly pop in and out of empty space, creating a background hiss of quantum noise that brings a level of uncertainty to LIGO's laser-based measurements. Quantum squeezing, which has roots in the late 1970s, is a method for hushing quantum noise or, more specifically, for pushing the noise from one place to another with the goal of making more precise measurements.

The term squeezing refers to the fact that light can be manipulated like a balloon animal. To make a dog or giraffe, one might pinch one section of a long balloon into a small precisely located joint. But then the other side of the balloon will swell out to a larger, less precise size. Light can similarly be squeezed to be more precise in one trait, such as its frequency, but the result is that it becomes more uncertain in another trait, such as its power. This limitation is based on a fundamental law of quantum mechanics called the uncertainty principle, which states that you cannot know both the position and momentum of objects (or the frequency and power of light) at the same time.

Since 2019, LIGO’s twin detectors have been squeezing light in such a way as to improve their sensitivity to the upper frequency range of gravitational waves they detect. But, in the same way that squeezing one side of a balloon results in the expansion of the other side, squeezing light has a price. By making LIGO’s measurements more precise at the high frequencies, the measurements became less precise at the lower frequencies.

“At some point, if you do more squeezing, you aren’t going to gain much. We needed to prepare for what was to come next in our ability to detect gravitational waves,” Barsotti explains.

Now, LIGO’s new frequency-dependent optical cavities — long tubes about the length of three football fields — allow the team to squeeze light in different ways depending on the frequency of gravitational waves of interest, thereby reducing noise across the whole LIGO frequency range.

“Before, we had to choose where we wanted LIGO to be more precise,” says LIGO team member Rana Adhikari, a professor of physics at Caltech. “Now we can eat our cake and have it too. We’ve known for a while how to write down the equations to make this work, but it was not clear that we could actually make it work until now. It’s like science fiction.”

Uncertainty in the quantum realm

Each LIGO facility is made up of two 4-kilometer-long arms connected to form an “L” shape. Laser beams travel down each arm, hit giant suspended mirrors, and then travel back to where they started. As gravitational waves sweep by Earth, they cause LIGO’s arms to stretch and squeeze, pushing the laser beams out of sync. This causes the light in the two beams to interfere with each other in a specific way, revealing the presence of gravitational waves.

However, the quantum noise that lurks inside the vacuum tubes that encase LIGO’s laser beams can alter the timing of the photons in the beams by minutely small amounts. McCuller likens this uncertainty in the laser light to a can of BBs. “Imagine dumping out a can full of BBs. They all hit the ground and click and clack independently. The BBs are randomly hitting the ground, and that creates a noise. The light photons are like the BBs and hit LIGO's mirrors at irregular times,” he said in a Caltech interview.

The squeezing technologies that have been in place since 2019 make “the photons arrive more regularly, as if the photons are holding hands rather than traveling independently,” McCuller said. The idea is to make the frequency, or timing, of the light more certain and the amplitude, or power, less certain as a way to tamp down the BB-like effects of the photons. This is accomplished with the help of specialized crystals that essentially turn one photon into a pair of two entangled, or connected, photons with lower energy. The crystals don’t directly squeeze light in LIGO’s laser beams; rather, they squeeze stray light in the vacuum of the LIGO tubes, and this light interacts with the laser beams to indirectly squeeze the laser light.

“The quantum nature of the light creates the problem, but quantum physics also gives us the solution,” Barsotti says.

An idea that began decades ago

The concept for squeezing itself dates back to the late 1970s, beginning with theoretical studies by the late Russian physicist Vladimir Braginsky; Kip Thorne, the Richard P. Feynman Professor of Theoretical Physics, Emeritus at Caltech; and Carlton Caves, professor emeritus at the University of New Mexico. The researchers had been thinking about the limits of quantum-based measurements and communications, and this work inspired one of the first experimental demonstrations of squeezing in 1986 by H. Jeff Kimble, the William L. Valentine Professor of Physics, Emeritus at Caltech. Kimble compared squeezed light to a cucumber; the certainty of the light measurements are pushed into only one direction, or feature, turning “quantum cabbages into quantum cucumbers,” he wrote in an article in Caltech’s Engineering & Science magazine in 1993.

In 2002, researchers began thinking about how to squeeze light in the LIGO detectors, and, in 2008, the first experimental demonstration of the technique was achieved at the 40-meter test facility at Caltech. In 2010, MIT researchers developed a preliminary design for a LIGO squeezer, which they tested at LIGO’s Hanford site. Parallel work done at the GEO600 detector in Germany also convinced researchers that squeezing would work. Nine years later, in 2019, after many trials and careful teamwork, LIGO began squeezing light for the first time.

“We went through a lot of troubleshooting,” says Sheila Dwyer, who has been working on the project since 2008, first as a graduate student at MIT and then as a scientist at the LIGO Hanford Observatory beginning in 2013. “Squeezing was first thought of in the late 1970s, but it took decades to get it right.”

Too much of a good thing

However, as noted earlier, there is a tradeoff that comes with squeezing. By moving the quantum noise out of the timing, or frequency, of the laser light, the researchers put the noise into the amplitude, or power, of the laser light. The more powerful laser beams then push LIGO’s heavy mirrors around causing a rumbling of unwanted noise corresponding to lower frequencies of gravitational waves. These rumbles mask the detectors’ ability to sense low-frequency gravitational waves.

“Even though we are using squeezing to put order into our system, reducing the chaos, it doesn't mean we are winning everywhere,” says Dhruva Ganapathy, a graduate student at MIT and one of four co-lead authors of the new study. “We are still bound by the laws of physics.” The other three lead authors of the study are MIT graduate student Wenxuan Jia, LIGO Livingston postdoc Masayuki Nakano, and MIT postdoc Victoria Xu.

Unfortunately, this troublesome rumbling becomes even more of a problem when the LIGO team turns up the power on its lasers. “Both squeezing and the act of turning up the power improve our quantum-sensing precision to the point where we are impacted by quantum uncertainty,” McCuller says. “Both cause more pushing of photons, which leads to the rumbling of the mirrors. Laser power simply adds more photons, while squeezing makes them more clumpy and thus rumbly.”

A win-win

The solution is to squeeze light in one way for high frequencies of gravitational waves and another way for low frequencies. It’s like going back and forth between squeezing a balloon from the top and bottom and from the sides.

This is accomplished by LIGO’s new frequency-dependent squeezing cavity, which controls the relative phases of the light waves in such a way that the researchers can selectively move the quantum noise into different features of light (phase or amplitude) depending on the frequency range of gravitational waves.

“It is true that we are doing this really cool quantum thing, but the real reason for this is that it's the simplest way to improve LIGO’s sensitivity,” Ganapathy says. “Otherwise, we would have to turn up the laser, which has its own problems, or we would have to greatly increase the sizes of the mirrors, which would be expensive.”

LIGO’s partner observatory, Virgo, will likely also use frequency-dependent squeezing technology within the current run, which will continue until roughly the end of 2024. Next-generation larger gravitational-wave detectors, such as the planned ground-based Cosmic Explorer, will also reap the benefits of squeezed light.

With its new frequency-dependent squeezing cavity, LIGO can now detect even more black hole and neutron star collisions. Ganapathy says he’s most excited about catching more neutron star smashups. “With more detections, we can watch the neutron stars rip each other apart and learn more about what’s inside.”

“We are finally taking advantage of our gravitational universe,” Barsotti says. “In the future, we can improve our sensitivity even more. I would like to see how far we can push it.”

The Physical Review X study is titled “Broadband quantum enhancement of the LIGO detectors with frequency-dependent squeezing.” Many additional researchers contributed to the development of the squeezing and frequency-dependent squeezing work, including Mike Zucker of MIT and GariLynn Billingsley of Caltech, the leads of the “Advanced LIGO Plus” upgrades that includes the frequency-dependent squeezing cavity; Daniel Sigg of LIGO Hanford Observatory; Adam Mullavey of LIGO Livingston Laboratory; and David McClelland’s group from the Australian National University.

The LIGO–Virgo–KAGRA Collaboration operates a network of gravitational-wave detectors in the United States, Italy, and Japan. LIGO Laboratory is operated by Caltech and MIT, and is funded by the NSF with contributions to the Advanced LIGO detectors from Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council), and Australia (Australian Research Council). Virgo is managed by the European Gravitational Observatory (EGO) and is funded by the Centre National de la Recherche Scientifique (CNRS) in France, the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and the National Institute for Subatomic Physics (Nikhef) in the Netherlands. KAGRA is hosted by the Institute for Cosmic Ray Research (ICRR) at the University of Tokyo and co-hosted by the National Astronomical Observatory of Japan (NAOJ) and the High Energy Accelerator Research Organization (KEK).


Wed, 18 Oct 2023 15:10:00 -0400

MIT receives major National Science Foundation grant for quantum science
Posted on Wednesday October 18, 2023

Category : Grants

Author : Sandi Miller | Department of Physics

Center for Ultracold Atoms gets funding boost to “punch through tough scientific barriers and see what's on the other side.”

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The U.S. National Science Foundation’s Physics Frontiers Centers program renewed a grant to the MIT-Harvard Center for Ultracold Atoms (CUA) to fund exploring, understanding, and harnessing mysterious phenomena at the frontiers of physics.

The CUA, which works to enable greater control and programmability of quantum-entangled systems of low-temperature atoms and molecules, will conduct experiments involving quantum gases of atoms and molecules; arrays of exotic atoms in Rydberg states containing a single, highly excited electron; atom-like impurities in semiconductors; and an “unusual” linking of light and matter known as "strong coupling" with the potential for new applications in measurement, sensing and networking.

“At MIT and Harvard, we are all excited to have continued funding for the Center for Ultracold Atoms, which has made a big difference for our community of researchers,” says Professor Wolfgang Ketterle, who added that it is critical to provide adequate funding for new projects and for junior individuals who have joined the CUA.

“CUA is one of the centerpieces of MIT’s strength in quantum science and measurement, and the renewal of the CUA grant is fantastic news,” says physics department head Deepto Chakrabarty.

Ketterle is a member of the CUA group receiving the funding, along with Vladan Vuletic, Martin W. Zwierlein, Paola Cappellaro, Isaac Chuang, Soonwon Choi, Richard Fletcher, and Dirk Englund.
The CUA is one of four U.S. research centers to be backed by a total of $76 million; the three other recipients are the University of Chicago, Caltech, and the University of Colorado at Boulder.

The NSF Physics Frontiers Centers program brings together large teams of researchers for projects that will require years of concentrated effort, a range of scientific and technical expertise, and new types of equipment. NSF now actively supports eight physics centers. 

The centers offer extensive training and mentorship programs for undergraduate and graduate students, as well as postdocs, to nurture future leaders in the field of physics and to strengthen the scientific workforce in the United States. Additionally, the centers also seek to boost middle and high school students’ interest in STEM careers via educational games, videos, workshops, summer schools, and outreach activities.

“Research teams at NSF Physics Frontiers Centers have made breakthrough after breakthrough, such as creating remarkable new states of matter and revealing the first evidence for the gravitational wave background of the universe,” says NSF Director Sethuraman Panchanathan. “While different in their respective areas of focus, NSF's newly funded centers are all bold team efforts to punch through to exciting new vistas of scientific exploration. Achieving transformative opportunities requires us to reach those vistas through new technologies and other advances and have a look around.”


Wed, 18 Oct 2023 11:00:00 -0400

From a five-layer graphene sandwich, a rare electronic state emerges
Posted on Wednesday October 18, 2023

Category : Electronics

Author : Jennifer Chu | MIT News

A newly discovered type of electronic behavior could help with packing more data into magnetic memory devices.

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Ordinary pencil lead holds extraordinary properties when shaved down to layers as thin as an atom. A single, atom-thin sheet of graphite, known as graphene, is just a tiny fraction of the width of a human hair. Under a microscope, the material resembles a chicken-wire of carbon atoms linked in a hexagonal lattice.

Despite its waif-like proportions, scientists have found over the years that graphene is exceptionally strong. And when the material is stacked and twisted in specific contortions, it can take on surprising electronic behavior.

Now, MIT physicists have discovered another surprising property in graphene: When stacked in five layers, in a rhombohedral pattern, graphene takes on a very rare, “multiferroic” state, in which the material exhibits both unconventional magnetism and an exotic type of electronic behavior, which the team has coined ferro-valleytricity.

“Graphene is a fascinating material,” says team leader Long Ju, assistant professor of physics at MIT. “Every layer you add gives you essentially a new material. And now this is the first time we see ferro-valleytricity, and unconventional magnetism, in five layers of graphene. But we don’t see this property in one, two, three, or four layers.”

The discovery could help engineers design ultra-low-power, high-capacity data storage devices for classical and quantum computers.

“Having multiferroic properties in one material means that, if it could save energy and time to write a magnetic hard drive, you could also store double the amount of information compared to conventional devices,” Ju says.

His team reports their discovery today in Nature. MIT co-authors include lead author Tonghang Han, plus Zhengguang Lu, Tianyi Han, and Liang Fu; along with Harvard University collaborators Giovanni Scuri, Jiho Sung, Jue Wang, and Hongkun Park; and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan.

A preference for order

A ferroic material is one that displays some coordinated behavior in its electric, magnetic, or structural properties. A magnet is a common example of a ferroic material: Its electrons can coordinate to spin in the same direction without an external magnetic field. As a result, the magnet points to a preferred direction in space, spontaneously.

Other materials can be ferroic through different means. But only a handful have been found to be multiferroic — a rare state in which multiple properties can coordinate to exhibit multiple preferred states. In conventional multiferroics, it would be as if, in addition to the magnet pointing toward one direction, the electric charge also shifts in a direction that is independent from the magnetic direction.  

Multiferroic materials are of interest for electronics because they could potentially increase the speed and lower the energy cost of hard drives. Magnetic hard drives store data in the form of magnetic domains — essentially, microscopic magnets that are read as either a 1 or a 0, depending on their magnetic orientation. The magnets are switched by an electric current, which consumes a lot of energy and cannot operate quickly. If a storage device could be made with multiferroic materials, the domains could be switched by a faster, much lower-power electric field. Ju and his colleagues were curious about whether multiferroic behavior would emerge in graphene. The material’s extremely thin structure is a unique environment in which researchers have discovered otherwise hidden, quantum interactions. In particular, Ju wondered whether graphene would display multiferroic, coordinated behavior among its electrons when arranged under certain conditions and configurations.

“We are looking for environments where electrons are slowed down — where their interactions with the surrounding lattice of atoms is small, so that their interactions with other electrons can come through,” Ju explains. “That’s when we have some chance of seeing interesting collective behaviors of electrons.”

The team carried out some simple calculations and found that some coordinated behavior among electrons should emerge in a structure of five graphene layers stacked together in a rhombohedral pattern. (Think of five chicken-wire fences, stacked and slightly shifted such that, viewed from the top, the structure would resemble a pattern of diamonds.)

“In five layers, electrons happen to be in a lattice environment where they move very slowly, so they can interact with other electrons effectively,” Ju says. “That’s when electron correlation effects start to dominate, and they can start to coordinate into certain preferred, ferroic orders.”

Magic flakes

The researchers then went into the lab to see whether they could actually observe multiferroic behavior in five-layer graphene. In their experiments, they started with a small block of graphite, from which they carefully exfoliated individual flakes. They used optical techniques to examine each flake, looking specifically for five-layer flakes, arranged naturally in a rhombohedral pattern.

“To some extent, nature does the magic,” said lead author and graduate student Han. “And we can look at all these flakes and tell which has five layers, in this rhombohedral stacking, which is what should give you this slowing-down effect in electrons.”

The team isolated several five-layer flakes and studied them at temperatures just above absolute zero. In such ultracold conditions, all other effects, such as thermally induced disorders within graphene, should be dampened, allowing interactions between electrons, to emerge. The researchers measured electrons’ response to an electric field and a magnetic field, and found that indeed, two ferroic orders, or sets of coordinated behaviors, emerged.

The first ferroic property was an unconventional magnetism: The electrons coordinated their orbital motion, like planets circling in the same direction. (In conventional magnets, electrons coordinate their “spin” — rotating in the same direction, while staying relatively fixed in space.)

The second ferroic property had to do with graphene’s electronic “valley.” In every conductive material, there are certain energy levels that electrons can occupy. A valley represents the lowest energy state that an electron can naturally settle. As it turns out, there are two possible valleys in graphene. Normally, electrons have no preference for either valley and settle equally into both.

But in five-layer graphene, the team found that the electrons began to coordinate, and preferred to settle in one valley over the other. This second coordinated behavior indicated a ferroic property that, combined with the electrons’ unconventional magnetism, gave the structure a rare, multiferroic state.

“We knew something interesting would happen in this structure, but we didn’t know exactly what, until we tested it,” says co-first author Lu, a postdoc in Ju’s group. “It’s the first time we’ve seen a ferro-valleytronics, and also the first time we’ve seen a coexistence of ferro-valleytronics with unconventional ferro-magnet.”

The team showed they could control both ferroic properties using an electric field. They envision that, if engineers can incorporate five-layer graphene or similar multiferroic materials into a memory chip, they could, in principle, use the same, low-power electric field to manipulate the material’s electrons in two ways rather than one, and effectively double the data that could be stored on a chip compared to conventional multiferroics. While that vision is far from practical realization, the team’s results break new ground in the search for better, more efficient electronic, magnetic and valleytronic devices.

This research was done, in part, using the electron-beam lithography facility run by MIT.nano, and is funded, in part, by the National Science Foundation and the Sloan Foundation.


Wed, 11 Oct 2023 17:15:00 -0400

Physicists coax superconductivity and more from quasicrystals
Posted on Wednesday October 11, 2023

Category : Research

Author : Elizabeth A. Thomson | Materials Research Laboratory

Flexible platform could produce enigmatic materials, lead to new studies of exotic phenomena.

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In research that could jump-start interest into an enigmatic class of materials known as quasicrystals, MIT scientists and colleagues have discovered a relatively simple, flexible way to create new atomically thin versions that can be tuned for important phenomena. In work reported in a recent issue of Nature, they describe doing just that to make the materials exhibit superconductivity and more.

The research introduces a new platform for not only learning more about quasicrystals, but also exploring exotic phenomena that can be hard to study but could lead to important applications and new physics. For example, a better understanding of superconductivity, in which electrons pass through a material with no resistance, could allow much more efficient electronic devices.

The work brings together two previously unconnected fields: quasicrystals and twistronics. The latter is the specialty of Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT and corresponding author of the new Nature paper, whose “magic-angle” graphene breakthrough in 2018 jump-started the field.

“It's really extraordinary that the field of twistronics keeps making unexpected connections to other areas of physics and chemistry, in this case the beautiful and exotic world of quasiperiodic crystals," says Jarillo-Herrero, who is also affiliated with MIT’s Materials Research Laboratory and the MIT Research Laboratory of Electronics.

Do the twist

Twistronics involves atomically thin layers of materials placed on top of one another. Rotating, or twisting, one or more of the layers at a slight angle creates a unique pattern called a moiré superlattice. And a moiré pattern, in turn, has an impact on the behavior of electrons. “It changes the spectrum of energy levels available to the electrons and can provide the conditions for interesting phenomena to arise,” says Sergio C. de la Barrera, one of four co-first authors of the recent paper. De la Barrera, who conducted the work while a postdoc at MIT, is now an assistant professor at the University of Toronto.

A moiré system can also be tailored for different behaviors by changing the number of electrons added to the system. As a result, the field of twistronics has exploded over the last five years as researchers around the world have applied it to creating new atomically thin quantum materials. Examples from MIT alone include:

  • Turning a moiré material known as magic-angle twisted bilayer graphene into three different — and useful — electronic devices. (The scientists involved in that work, reported in 2021, included Daniel Rodan-Legrain, a co-first author of the current work and an MIT postdoc in physics. They were led by Jarillo-Herrero.)
  • Engineering a new property, ferroelectricity, into a well-known family of semiconductors. (The scientists involved in that work, reported in 2021, were led by Jarillo-Herrero.)
  • Predicting exotic new magnetic phenomena, complete with a “recipe” for realizing them. (The scientists involved in that work, reported in 2023, included MIT professor of physics Liang Fu and Nisarga Paul, an MIT graduate student in physics. Both Fu and Paul are co-authors of the current paper.)

Toward new quasicrystals

In the current work, the researchers were tinkering with a moiré system made of three sheets of graphene. Graphene is composed of a single layer of carbon atoms arranged in hexagons resembling a honeycomb structure. In this case, the team layered three sheets of graphene on top of one another, but twisted two of the sheets at slightly different angles.

To their surprise, the system created a quasicrystal, an unusual class of material discovered in the 1980s. As the name implies, quasicrystals are somewhere between a crystal, such as a diamond, that has a regular repeating structure, and an amorphous material, like glass, “where the atoms are all jumbled, or randomly arranged,” says de la Barrera. In a nutshell, quasicrystals “have really strange patterns,” de la Barrera says (see some examples here).

Compared to crystals and amorphous materials, however, relatively little is known about quasicrystals. That’s in part because they’re hard to make. “That doesn’t mean they’re not interesting; it just means that we haven’t paid as much attention to them, particularly to their electronic properties,” says de la Barrera. The new platform, which is relatively simple, could change that.

Learning more

Because the original researchers weren’t experts in quasicrystals, they reached out to someone who is: Professor Ron Lifshitz of Tel Aviv University. Aviram Uri, one of the co-first authors of the paper and an MIT Pappalardo and VATAT Postdoctoral Fellow, was a student of Lifshitz’s during his undergraduate studies at Tel Aviv and knew about his work on quasicrystals. Lifshitz, who is also an author of the Nature paper, helped the team to better understand what they were looking at, which they call a moiré quasicrystal.

The physicists then tuned a moiré quasicrystal to make it superconducting, or transmit current with no resistance at all below a certain low temperature. That’s important because superconducting devices could transfer current through electronic devices much more efficiently than is possible today, but the phenomenon is still not fully understood in all cases. The new moiré quasicrystal system brings a new way to study it.

The team also found evidence of symmetry breaking, another phenomenon that “tells us that the electrons are interacting with one another very strongly. And as physicists and quantum material scientists, we want our electrons interacting with each other because that’s where the exotic physics happens,” de la Barrera says.

In the end, “through discussions across continents we were able to decipher this thing, and now we believe we have a good handle on what’s going on,” says Uri, although he notes that “we don’t yet fully understand the system. There are still quite a few mysteries.”

The best part of the research was “solving the puzzle of what it was we had actually created,” de la Barrera says. “We were expecting [something else], so it was a very pleasant surprise when we realized we were actually looking at something very new and different.”

“It’s the same answer for me,” says Uri.

Additional authors of the Nature paper are MIT professor of physics Raymond C. Ashoori; Mallika T. Randeria, a researcher at MIT Lincoln Laboratory who conducted the work as a Pappalardo Fellow at MIT and is another co-first author of the paper; Trithep Devakul, an assistant professor at Stanford University who conducted the work as a postdoc at MIT; Philip J. D. Crowley, a postdoc at Harvard University; and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan.

This work was funded by the U.S. Army Research Office, the U.S. National Science Foundation, the Gordon and Betty Moore Foundation, a MIT Pappalardo Fellowship, a VATAT Outstanding Postdoctoral Fellowship in Quantum Science and Technology, the JSPS KAKENHI, and the Israel Science Foundation.


Mon, 09 Oct 2023 15:00:00 -0400

Boom, crackle, pop: Sounds of Earth’s crust
Posted on Monday October 09, 2023

Category : Research

Author : Jennifer Chu | MIT News

MIT scientists find the sounds beneath our feet are fingerprints of rock stability.

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If you could sink through the Earth’s crust, you might hear, with a carefully tuned ear, a cacophany of booms and crackles along the way. The fissures, pores, and defects running through rocks are like strings that resonate when pressed and stressed. And as a team of MIT geologists has found, the rhythm and pace of these sounds can tell you something about the depth and strength of the rocks around you.

“If you were listening to the rocks, they would be singing at higher and higher pitches, the deeper you go,” says MIT geologist Matěj Peč.

Peč and his colleagues are listening to rocks, to see whether any acoustic patterns, or “fingerprints” emerge when subjected to various pressures. In lab studies, they have now shown that samples of marble, when subjected to low pressures, emit low-pitched “booms,” while at higher pressures, the rocks generate an ‘avalanche’ of higher-pitched crackles.

Peč says these acoustic patterns in rocks can help scientists estimate the types of cracks, fissures, and other defects that the Earth’s crust experiences with depth, which they can then use to identify unstable regions below the surface, where there is potential for earthquakes or eruptions. The team’s results, published today in the Proceedings of the National Academy of Sciences, could also help inform surveyors’ efforts to drill for renewable, geothermal energy.

“If we want to tap these very hot geothermal sources, we will have to learn how to drill into rocks that are in this mixed-mode condition, where they are not purely brittle, but also flow a bit,” says Peč, who is an assistant professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “But overall, this is fundamental science that can help us understand where the lithosphere is strongest.”

Peč’s collaborators at MIT are lead author and research scientist Hoagy O. Ghaffari, technical associate Ulrich Mok, graduate student Hilary Chang, and professor emeritus of geophysics Brian Evans. Tushar Mittal, co-author and former EAPS postdoc, is now an assistant professor at Penn State University.

Fracture and flow

The Earth’s crust is often compared to the skin of an apple. At its thickest, the crust can be 70 kilometers deep — a tiny fraction of the globe’s total, 12,700-kilometer diameter. And yet, the rocks that make up the planet’s thin peel vary greatly in their strength and stability. Geologists infer that rocks near the surface are brittle and fracture easily, compared to rocks at greater depths, where immense pressures, and heat from the core, can make rocks flow.

The fact that rocks are brittle at the surface and more ductile at depth implies there must be an in-between — a phase in which rocks transition from one to the other, and may have properties of both, able to fracture like granite, and flow like honey. This “brittle-to-ductile transition” is not well understood, though geologists believe it may be where rocks are at their strongest within the crust.

“This transition state of partly flowing, partly fracturing, is really important, because that’s where we think the peak of the lithosphere’s strength is and where the largest earthquakes nucleate,” Peč says. “But we don’t have a good handle on this type of mixed-mode behavior.”

He and his colleagues are studying how the strength and stability of rocks — whether brittle, ductile, or somewhere in between — varies, based on a rock’s microscopic defects. The size, density, and distribution of defects such as microscopic cracks, fissures, and pores can shape how brittle or ductile a rock can be.

But measuring the microscopic defects in rocks, under conditions that simulate the Earth’s various pressures and depths, is no trivial task. There is, for instance, no visual-imaging technique that allows scientists to see inside rocks to map their microscopic imperfections. So the team turned to ultrasound, and the idea that, any sound wave traveling through a rock should bounce, vibrate, and reflect off any microscopic cracks and crevices, in specific ways that should reveal something about the pattern of those defects.

All these defects will also generate their own sounds when they move under stress and therefore both actively sounding through the rock as well as listening to it should give them a great deal of information. They found that the idea should work with ultrasound waves, at megahertz frequencies.

This kind of ultrasound method is analogous to what seismologists do in nature, but at much higher frequencies,” Peč explains. “This helps us to understand the physics that occur at microscopic scales, during the deformation of these rocks.”

A rock in a hard place

In their experiments, the team tested cylinders of Carrara marble.

“It’s the same material as what Michaelangelo’s David is made from,” Peč notes. “It’s a very well-characterized material, and we know exactly what it should be doing.”

The team placed each marble cylinder in a a vice-like apparatus made from pistons of aluminum, zirconium, and steel, which together can generate extreme stresses. They placed the vice in a pressurized chamber, then subjected each cylinder to pressures similar to what rocks experience throughout the Earth’s crust. 

As they slowly crushed each rock, the team sent pulses of ultrasound through the top of the sample, and recorded the acoustic pattern that exited through the bottom. When the sensors were not pulsing, they were listening to any naturally occurring acoustic emissions.

They found that at the lower end of the pressure range, where rocks are brittle, the marble indeed formed sudden fractures in response, and the sound waves resembled large, low-frequency booms. At the highest pressures, where rocks are more ductile, the acoustic waves resembled a higher-pitched crackling. The team believes this crackling was produced by microscopic defects called dislocations that then spread and flow like an avalanche.

“For the first time, we have recorded the ‘noises’ that rocks make when they are deformed across this brittle-to-ductile transition, and we link these noises to the individual microscopic defects that cause them,” Peč says. “We found that these defects massively change their size and propagation velocity as they cross this transition. It’s more complicated than people had thought.”

The team’s characterizations of rocks and their defects at various pressures can help scientists estimate how the Earth’s crust will behave at various depths, such as how rocks might fracture in an earthquake, or flow in an eruption.    

“When rocks are partly fracturing and partly flowing, how does that feed back into the earthquake cycle? And how does that affect the movement of magma through a network of rocks?” Peč says. “Those are larger scale questions that can be tackled with research like this.”

This research was supported, in part, by the National Science Foundation.


Wed, 27 Sep 2023 16:00:00 -0400

MIT welcomes nine MLK Visiting Professors and Scholars for 2023-24
Posted on Wednesday September 27, 2023

Category : MLK visiting scholars

Author : Beatriz Cantada | Institute Community and Equity Office

Martin Luther King Jr. Visiting Professors and Scholars will enhance and enrich the MIT community through engagement with students and faculty.

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Established in 1990, the MLK Visiting Professors and Scholars Program at MIT welcomes outstanding scholars to the Institute for visiting appointments. MIT aspires to attract candidates who are, in the words of Martin Luther King Jr., “trailblazers in human, academic, scientific and religious freedom.” The program honors King’s life and legacy by expanding and extending the reach of our community. 

The MLK Scholars Program has welcomed more than 140 professors, practitioners, and professionals at the forefront of their respective fields to MIT. They contribute to the growth and enrichment of the community through their interactions with students, staff, and faculty. They pay tribute to Martin Luther King Jr.’s life and legacy of service and social justice, and they embody MIT’s values: excellence and curiosity, openness and respect, and belonging and community.  

Each new cohort of scholars actively participates in community engagement and supports MIT’s mission of “advancing knowledge and educating students in science, technology, and other areas of scholarship that will best serve the nation and the world in the 21st century." 

The 2023-2024 MLK Scholars:

Tawanna Dillahunt is an associate professor at the University of Michigan’s School of Information with a joint appointment in their electrical engineering and computer science department. She is joining MIT at the end of a one-year visiting appointment as a Harvard Radcliffe Fellow. Her faculty hosts at the Institute are Catherine D’Ignazio in the Department of Urban Studies and Planning and Fotini Christia in the Institute for Data, Systems, and Society (IDSS). Dillahunt’s research focuses on equitable and inclusive computing. During her appointment, she will host a podcast to explore ethical and socially responsible ways to engage with communities, with a special emphasis on technology. 

Kwabena Donkor is an assistant professor of marketing at Stanford Graduate School of Business; he is hosted by Dean Eckles, an associate professor of marketing at MIT Sloan School of Management. Donkor’s work bridges economics, psychology, and marketing. His scholarship combines insights from behavioral economics with data and field experiments to study social norms, identity, and how these constructs interact with policy in the marketplace.

Denise Frazier joins MIT from Tulane University, where she is an assistant director in the New Orleans Center for the Gulf South. She is a researcher and performer and brings a unique interdisciplinary approach to her work at the intersection of cultural studies, environmental justice, and music. Frazier is hosted by Christine Ortiz, the Morris Cohen Professor in the Department of Materials Science and Engineering. 

Wasalu Jaco, an accomplished performer and artist, is renewing his appointment at MIT for a second year; he is hosted jointly by Nick Montfort, a professor of digital media in the Comparative Media Studies Program/Writing, and Mary Fuller, a professor in the Literature Section and the current chair of the MIT faculty. In his second year, Jaco will work on Cyber/Cypher Rapper, a research project to develop a computational system that participates in responsive and improvisational rap.

Morgane Konig first joined the Center for Theoretical Physics at MIT in December 2021 as a postdoc. Now a member of the 2023–24 MLK Visiting Scholars Program cohort, she will deepen her ties with scholars and research groups working in cosmology, primarily on early-universe inflation and late-universe signatures that could enable the scientific community to learn more about the mysterious nature of dark matter and dark energy. Her faculty hosts are David Kaiser, the Germeshausen Professor of the History of Science and professor of physics, and Alan Guth, the Victor F. Weisskopf Professor of Physics, both from the Department of Physics.

The former minister of culture for Colombia and a transformational leader dedicated to environmental protection, Angelica Mayolo-Obregon joins MIT from Buenaventura, Colombia. During her time at MIT, she will serve as an advisor and guest speaker, and help MIT facilitate gatherings of environmental leaders committed to addressing climate action and conserving biodiversity across the Americas, with a special emphasis on Afro-descendant communities. Mayolo-Obregon is hosted by John Fernandez, a professor of building technology in the Department of Architecture and director of MIT's Environmental Solutions Initiative, and by J. Phillip Thompson, an associate professor in the Department of Urban Studies and Planning (and a former MLK Scholar).

Jean-Luc Pierite is a member of the Tunica-Biloxi Tribe of Louisiana and the president of the board of directors of North American Indian Center of Boston. While at MIT, Pierite will build connections between MIT and the local Indigenous communities. His research focuses on enhancing climate resilience planning by infusing Indigenous knowledge and ecological practices into scientific and other disciplines. His faculty host is Janelle Knox-Hayes, the Lister Brothers Professor of Economic Geography and Planning in the Department of Urban Studies and Planning.

Christine Taylor-Butler ’81 is a children’s book author who has written over 90 books; she is hosted by Graham Jones, an associate professor of anthropology. An advocate for literacy and STEAM education in underserved urban and rural schools, Taylor-Butler will partner with community organizations in the Boston area. She is also completing the fourth installment of her middle-grade series, "The Lost Tribe." These books follow a team of five kids as they use science and technology to crack codes and solve mysteries.

Angelino Viceisza, a professor of economics at Spelman College, joins MIT Sloan as an MLK Visiting Professor and the Phyllis Wallace Visiting Professor; he is hosted by Robert Gibbons, Sloan Distinguished Professor of Management, and Ray Reagans, Alfred P. Sloan Professor of Management, professor of organization studies, and associate dean for diversity, equity, and inclusion at MIT Sloan. Viceisza has strong, ongoing connections with MIT. His research focuses on remittances, retirement, and household finance in low-income countries and is relevant to public finance and financial economics, as well as the development and organizational economics communities at MIT. 

Javit Drake, Moriba Jah, and Louis Massiah, members of last year’s cohort of MLK Scholars, will remain at MIT through the end of 2023.

There are multiple opportunities throughout the year to meet our MLK Visiting Scholars and learn more about their research projects and their social impact. 

For more information about the MLK Visiting Professors and Scholars Program and upcoming events, visit the website.


Wed, 27 Sep 2023 09:15:00 -0400

From physics to generative AI: An AI model for advanced pattern generation
Posted on Wednesday September 27, 2023

Category : Research

Author : Rachel Gordon | MIT CSAIL

Inspired by physics, a new generative model PFGM++ outperforms diffusion models in image generation.

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Generative AI, which is currently riding a crest of popular discourse, promises a world where the simple transforms into the complex — where a simple distribution evolves into intricate patterns of images, sounds, or text, rendering the artificial startlingly real. 

The realms of imagination no longer remain as mere abstractions, as researchers from MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) have brought an innovative AI model to life. Their new technology integrates two seemingly unrelated physical laws that underpin the best-performing generative models to date: diffusion, which typically illustrates the random motion of elements, like heat permeating a room or a gas expanding into space, and Poisson Flow, which draws on the principles governing the activity of electric charges.

This harmonious blend has resulted in superior performance in generating new images, outpacing existing state-of-the-art models. Since its inception, the “Poisson Flow Generative Model ++” (PFGM++) has found potential applications in various fields, from antibody and RNA sequence generation to audio production and graph generation.

The model can generate complex patterns, like creating realistic images or mimicking real-world processes. PFGM++ builds off of PFGM, the team’s work from the prior year. PFGM takes inspiration from the means behind the mathematical equation known as the “Poisson” equation, and then applies it to the data the model tries to learn from. To do this, the team used a clever trick: They added an extra dimension to their model's “space,” kind of like going from a 2D sketch to a 3D model. This extra dimension gives more room for maneuvering, places the data in a larger context, and helps one approach the data from all directions when generating new samples. 

“PFGM++ is an example of the kinds of AI advances that can be driven through interdisciplinary collaborations between physicists and computer scientists,” says Jesse Thaler, theoretical particle physicist in MIT’s Laboratory for Nuclear Science's Center for Theoretical Physics and director of the National Science Foundation's AI Institute for Artificial Intelligence and Fundamental Interactions (NSF AI IAIFI), who was not involved in the work. “In recent years, AI-based generative models have yielded numerous eye-popping results, from photorealistic images to lucid streams of text. Remarkably, some of the most powerful generative models are grounded in time-tested concepts from physics, such as symmetries and thermodynamics. PFGM++ takes a century-old idea from fundamental physics — that there might be extra dimensions of space-time — and turns it into a powerful and robust tool to generate synthetic but realistic datasets. I'm thrilled to see the myriad of ways ‘physics intelligence’ is transforming the field of artificial intelligence.”

The underlying mechanism of PFGM isn't as complex as it might sound. The researchers compared the data points to tiny electric charges placed on a flat plane in a dimensionally expanded world. These charges produce an “electric field,” with the charges looking to move upwards along the field lines into an extra dimension and consequently forming a uniform distribution on a vast imaginary hemisphere. The generation process is like rewinding a videotape: starting with a uniformly distributed set of charges on the hemisphere and tracking their journey back to the flat plane along the electric lines, they align to match the original data distribution. This intriguing process allows the neural model to learn the electric field, and generate new data that mirrors the original. 

The PFGM++ model extends the electric field in PFGM to an intricate, higher-dimensional framework. When you keep expanding these dimensions, something unexpected happens — the model starts resembling another important class of models, the diffusion models. This work is all about finding the right balance. The PFGM and diffusion models sit at opposite ends of a spectrum: one is robust but complex to handle, the other simpler but less sturdy. The PFGM++ model offers a sweet spot, striking a balance between robustness and ease of use. This innovation paves the way for more efficient image and pattern generation, marking a significant step forward in technology. Along with adjustable dimensions, the researchers proposed a new training method that enables more efficient learning of the electric field. 

To bring this theory to life, the team resolved a pair of differential equations detailing these charges’ motion within the electric field. They evaluated the performance using the Frechet Inception Distance (FID) score, a widely accepted metric that assesses the quality of images generated by the model in comparison to the real ones. PFGM++ further showcases a higher resistance to errors and robustness toward the step size in the differential equations.

Looking ahead, they aim to refine certain aspects of the model, particularly in systematic ways to identify the “sweet spot” value of D tailored for specific data, architectures, and tasks by analyzing the behavior of estimation errors of neural networks. They also plan to apply the PFGM++ to the modern large-scale text-to-image/text-to-video generation.

“Diffusion models have become a critical driving force behind the revolution in generative AI,” says Yang Song, research scientist at OpenAI. “PFGM++ presents a powerful generalization of diffusion models, allowing users to generate higher-quality images by improving the robustness of image generation against perturbations and learning errors. Furthermore, PFGM++ uncovers a surprising connection between electrostatics and diffusion models, providing new theoretical insights into diffusion model research.”

“Poisson Flow Generative Models do not only rely on an elegant physics-inspired formulation based on electrostatics, but they also offer state-of-the-art generative modeling performance in practice,” says NVIDIA Senior Research Scientist Karsten Kreis, who was not involved in the work. “They even outperform the popular diffusion models, which currently dominate the literature. This makes them a very powerful generative modeling tool, and I envision their application in diverse areas, ranging from digital content creation to generative drug discovery. More generally, I believe that the exploration of further physics-inspired generative modeling frameworks holds great promise for the future and that Poisson Flow Generative Models are only the beginning.”

Authors on a paper about this work include three MIT graduate students: Yilun Xu of the Department of Electrical Engineering and Computer Science (EECS) and CSAIL, Ziming Liu of the Department of Physics and the NSF AI IAIFI, and Shangyuan Tong of EECS and CSAIL, as well as Google Senior Research Scientist Yonglong Tian PhD '23. MIT professors Max Tegmark and Tommi Jaakkola advised the research.

The team was supported by the MIT-DSTA Singapore collaboration, the MIT-IBM Watson AI Lab, National Science Foundation grants, The Casey and Family Foundation, the Foundational Questions Institute, the Rothberg Family Fund for Cognitive Science, and the ML for Pharmaceutical Discovery and Synthesis Consortium. Their work was presented at the International Conference on Machine Learning this summer.


Tue, 26 Sep 2023 16:50:00 -0400

Five MIT faculty members named 2023 Simons Investigators
Posted on Tuesday September 26, 2023

Category : Faculty

Author : Sandi Miller | Jane Halpern | Department of Mathematics | Department of Physics | Department of Electrical Engineering and Computer Science

The program supports “outstanding theoretical scientists.”

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Five MIT professors have been selected to receive the 2023 Simons Investigators awards from the Simons Foundation. Virginia Vassilevska Williams and Vinod Vaikuntanathan are both professors in MIT’s Department of Electrical Engineering and Computer Science (EECS) and principal investigators in MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL). Aram Harrow and Leonid Mirny are professors in the Department of Physics, and Davesh Maulik is a professor in the Department of Mathematics.

The Simons Investigator program supports “outstanding theoretical scientists who receive a stable base of research support from the foundation, enabling them to undertake the long-term study of fundamental questions.”

Aram Harrow '01, PhD '05, professor of physics, studies theoretical quantum information science in order to understand the capabilities of quantum computers and quantum communication devices. Harrow has developed quantum algorithms for solving large systems of linear equations and hybrid classical-quantum algorithms for machine learning, and has also contributed to the intersection of quantum information and many-body physics, with work on thermalization, random quantum dynamics, and the “monogamy” property of quantum entanglement. He was a lecturer at the University of Bristol and a research assistant professor at the University of Washington until joining MIT in 2013. His awards include the NSF CAREER award, several best paper awards, an APS Outstanding Referee Award, and the APS Rolf Landauer and Charles H Bennett Award in Quantum Computing.

Davesh Maulik joined the Department of Mathematics at MIT in 2015. He works in algebraic geometry, with an emphasis on the geometry of moduli spaces. In many cases, this involves using ideas from neighboring fields such as representation theory, symplectic geometry, and number theory. His most recent work has focused on moduli spaces of Higgs bundles and various conjectures regarding their structure. In the past, he has received a Clay Mathematics Research Fellowship and the Compositio Mathematica Prize with coauthors for an outstanding research publication.

Leonid Mirny, the Richard J. Cohen (1976) Professor in Medicine and Biomedical Physics, is a core faculty member at the Institute for Medical Engineering and Science (IMES), and is faculty at the Department of Physics. His work combines biophysical modeling with analysis of large genomics data to address fundamental problems in biology. Mirny aims to understand how exceedingly long molecules of DNA are folded in 3D, and how this 3D folding of the genome influences gene expression and execution of genetic programs in health and disease. His prediction that the genome is folded by a new class of motors that act by “loop extrusion” was experimentally confirmed, leading a paradigm shift in chromosome biology. Broadly, Mirny is interested in unraveling physical mechanisms that underlie reading, writing, and transmission of genetic and epigenetic information. He was awarded the 2019 Blaise Pascal International Chair of Excellence and was named a Fellow of the American Physical Society. He received his MS in chemistry from the Weizmann Institute of Science, and his PhD in biophysics from Harvard University, where he also served as a junior fellow at Harvard Society of Fellows.

Vinod Vaikuntanathan is a professor of computer science at MIT. The co-inventor of modern fully homomorphic encryption systems and many other lattice-based (and post-quantum secure) cryptographic primitives, Vaikuntanathan’s work has been recognized with a George M. Sprowls PhD thesis award, an IBM Josef Raviv Fellowship, a Sloan Faculty Fellowship, a Microsoft Faculty Fellowship, an NSF CAREER Award, a DARPA Young Faculty Award, a Harold E. Edgerton Faculty Award, Test of Time awards from IEEE FOCS and CRYPTO conferences, and a Gödel prize. Vaikuntanathan earned his SM and PhD degrees from MIT, and a BTech degree from the Indian Institute of Technology Madras.

Virginia Vassilevska Williams is a professor of computer science at MIT EECS. Williams’s research focuses on algorithm design and analysis of fundamental problems involving graphs, matrices and more, seeking to determine the precise (asymptotic) time complexity of these problems. She has designed the fastest algorithm for matrix multiplication and is widely regarded as the leading expert on fine-grained complexity. Among her many awards, she has received an NSF CAREER award; a Sloan Research Fellowship; a Google Faculty Research Award, a Thornton Family Faculty Research Innovation Fellowship (FRIF), and was an invited speaker at the International Congress of Mathematicians in 2018. Williams earned her MS and PhD degrees at Carnegie Mellon University, and her BS degree at Caltech.


Mon, 25 Sep 2023 15:55:00 -0400

School of Science welcomes new faculty in 2023
Posted on Monday September 25, 2023

Category : Faculty

Author : School of Science

Sixteen professors join the departments of Biology; Chemistry; Earth, Atmospheric and Planetary Sciences; Mathematics; and Physics.

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Last spring, the School of Science welcomed seven new faculty members.

Erin Chen PhD ’11 studies the communication between microbes that reside on the surface of the human body and the immune system. She focuses on the largest organ: the skin. Chen will dissect the molecular signals of diverse skin microbes and their effects on host tissues, with the goal of harnessing microbe-host interactions to engineer new therapeutics for human disease.

Chen earned her bachelor’s in biology from the University of Chicago, her PhD from MIT, and her MD from Harvard Medical School, and she completed her medical residency at the University of California at San Francisco. Chen was also a Howard Hughes Medical Institute Hanna Gray Fellow at Stanford University and an attending dermatologist at UCSF and at the San Francisco VA Medical Center. Chen returns to MIT as an assistant professor in the Department of Biology, a core member of the Broad Institute of MIT and Harvard, and an attending dermatologist at Massachusetts General Hospital.

Robert Gilliard’s research is multidisciplinary and combines various aspects of organic, inorganic, main-group, and materials chemistry. The Gilliard group specializes in the chemical synthesis of new molecules that impact the development of new catalysts and reagents, including the discovery of unknown transformations of environmentally relevant small-molecules [e.g., carbon dioxide, carbon monoxide, and dihydrogen (H2)]. In addition, he investigates the design, characterization, and reactivity of boron-based luminescent and redox-active heterocycles for use in optoelectronic applications (e.g., stimuli-responsive materials, thermochromic materials, chemical sensors).

Gilliard earned his bachelor’s degree from Clemson University and his PhD from the University of Georgia. He completed joint postdoctoral studies at the Swiss Federal Institute of Technology (ETH Zürich) and Case Western Reserve University. He served on the faculty at the University of Virginia from 2017-22. Gilliard spent time in the MIT Department of Chemistry as a 2021-22 Dr. Martin Luther King Visiting Professor. He returns as the Novartis Associate Professor of Chemistry with tenure.

Sally Kornbluth is president of MIT and a professor of biology. Before she closed her lab to focus on administration, her research focused on the biological signals that tell a cell to start dividing or to self-destruct — processes that are key to understanding cancer as well as various degenerative disorders. She has published extensively on cell proliferation and programmed cell death, studying both phenomena in a variety of organisms. Her research has helped to show how cancer cells evade this programmed death, or apoptosis, and how metabolism regulates the cell death process; her work has also clarified the role of apoptosis in regulating the duration of female fertility in vertebrates.

Kornbluth holds bachelor’s degrees in political science from Williams College and in genetics from Cambridge University. She earned her PhD in molecular oncology from Rockefeller University in 1989 and completed postdoctoral training at the University of California at San Diego. In 1994, she joined the faculty of Duke University and served in the administration as vice dean for basic science at the Duke School of Medicine (2006-2014) and later as the university's provost (2014-2022). She is a member of the National Academy of Medicine, the National Academy of Inventors, and the American Academy of Arts and Sciences.

Daniel Lew uses fungal model systems to ask how cells orient their activities in space, including oriented growth, cell wall remodeling, and organelle segregation. Different cells take on an astonishing variety of shapes, which are often critical to be able to perform specialized cell functions like absorbing nutrients or contracting muscles. Lew studies how different cell shapes arise and how cells control the spatial distribution of their internal constituents, taking advantage of the tractability of fungal model systems, and addressing these questions using approaches from cell biology, genetics, and computational biology to understand molecular mechanisms.

Lew received a bachelor’s degree in genetics from Cambridge University followed by a PhD in molecular biology from Rockefeller University. After postdoctoral training at the Scripps Research Institute, he joined the Duke University faculty in 1994. Lew joins MIT as a professor of biology with tenure.

Eluned Smith uses rare beauty decays measured with the LHCb detector at CERN to search for new fundamental particles at mass scales above the collision energy of the Large Hadron Collider (LHC). Her group leverages data to elucidate the physics of beauty quarks, whose behavior cannot be explained by the Standard Model of particle physics. In doing so, her work aims to resolve whether the anomalies are misunderstood quantum chromodynamics or the first sign of beyond-the-Standard-Model-physics at the LHC.

Smith joins MIT as an assistant professor in the Department of Physics and the Laboratory for Nuclear Science. She earned her undergraduate and doctoral degrees at Imperial College London, which she completed in 2017. She did her first postdoc at RWTH Aachen before winning an Ambizione Fellowship from the Swiss National Science Foundation at the University of Zürich.

Gaia Stucky de Quay explores topographic signals and landscape evolution, in order to both de-convolve and quantify primary driving forces such as tectonics, climate, and local geological processes. She integrates fieldwork, lab work, modeling, and remote sensing to improve our quantitative understanding of such processes at compelling geological sites such as Martian valleys and lakes, the surfaces of icy moons, and volcanic islands in the Atlantic Ocean.

Stucky de Quay joins the Department of Earth, Atmospheric and Planetary Sciences as an assistant professor. Most recently, she was a Daly Postdoctoral Fellow at Harvard University. Previously, she was a postdoc at the University of Texas at Austin and a visiting student at the University of Chicago. Stucky de Quay earned her MS from the University College of London and a PhD from Imperial College London.

Brandon "Brady" Weissbourd uses the jellyfish, Clytia hemisphaerica, to study nervous system evolution, development, regeneration, and function. With a foundation is in systems neuroscience, his lab uses genetic and optical techniques to examine how behavior arises from the activity of networks of neurons; they investigate how the Clytia nervous system is so robust; and they use Clytia’s evolutionary position to make inferences about the ultimate origins of nervous systems.

Weissbourd received a BA in human evolutionary biology from Harvard University in 2009 and a PhD from Stanford University in 2016. He then completed postdoctoral research at Caltech and The Howard Hughes Medical Institute. He joins MIT as an assistant professor in the Department of Biology and an investigator in The Picower Institute for Learning and Memory.

This fall, the School of Science welcomes nine new faculty members.

Facundo Batista studies the fundamental biology of the immune system to develop the next generation of vaccines and therapeutics. B lymphocytes are the fulcrum of immunological memory, the source of antibodies, and the focus of vaccine development. His lab has investigated how, where, and when B cell responses take shape. In recent years, the Batista group has expanded into preclinical vaccinology, targeting viruses including HIV, malaria, influenza, and SARS-CoV-2.

Batista is an MIT professor of biology with tenure as well as the associate director and scientific director of the Ragon Institute of MGH, MIT, and Harvard. He received his PhD from the International School of Advanced Studies in Trieste, Italy, and his undergraduate degree from the University of Buenos Aires, Argentina. Prior to MIT, Batista was a tenured member of the Francis Crick Institute, a professor at Imperial College London, and a professor of microbiology and immunology at Harvard Medical School.

Anna-Christina Eilers is an observational astrophysicist. Her research focuses on the formation of the first galaxies, quasars, and supermassive black holes in the early universe, during an era known as the Cosmic Dawn. In particular, Eilers is interested in the growth of the first supermassive black holes which reside in the center of luminous, distant galaxies known as quasars, to understand how black holes evolve from small stellar remnants to billion-solar-mass black holes within very short amounts of cosmic time.

Previously, Eilers received a bachelor’s degree in physics from the University of Goettingen, a master’s degree in astrophysics from the University of Heidelberg, and a PhD in astrophysics from the Max Planck Institute for Astronomy in Heidelberg. In 2019, she was awarded a NASA Hubble Fellowship and the Pappalardo Fellowship to continue her research at MIT. Eilers remains at MIT as an assistant professor in the Department of Physics and the MIT Kavli Institute for Astrophysics and Space Research.

Masha Elkin combines catalyst development, natural products synthesis, and machine learning to tackle important chemical challenges. Her group develops new transition metal catalysts that enable efficient bond disconnections and access to value-added compounds, leveraging these transformations for the synthesis of bioactive natural products that address outstanding needs in human health, and uses computational tools to explore all possible molecules and accelerate reaction discovery.

Elkin joins MIT as the D. Reid (1941) and Barbara J. Weedon Career Development Assistant Professor of Chemistry. She earned her bachelor’s degree in chemistry from Washington University in St. Louis in 2014, and her PhD from Yale University in 2019, then began as a postdoc at the University of California at Berkeley.

Mikhail Ivanov’s research has developed at the interface of theoretical physics and data analysis, bridging state-of-the-art theoretical ideas with observational data. The overarching aim of his research is to use Effective Field Theory in combination with astrophysical data in order to resolve fundamental challenges of modern physics, such as the nature of dark matter, dark energy, inflation, and gravity.

Ivanov joins MIT as an assistant professor in the Department of Physics and the Center for Theoretical Physics in the Laboratory for Nuclear Science. He obtained his PhD from the École Polytechnique Fédérale de Lausanne in 2019. During his PhD studies, he spent a year at the Institute for Advanced Study in Princeton, New Jersey, as a fellow of the Swiss National Science Foundation. Subsequently, he was a postdoc at New York University and a NASA Einstein Fellow at the Institute for Advanced Study.

Oleta Johnson joins the Department of Chemistry as an assistant professor. Efforts to target pathogenic proteins with drugs or chemical probes can often be analogized to a lock and key, where the protein target is the “lock” and the molecule is the “key.” However, what happens when the target is flexible or lacks a defined structure? In all living things, molecular chaperone proteins have evolved to support proper folding of these moving targets. Yet, protein misfolding and aggregation is a hallmark of many myopathies and neurodegenerative diseases. Johnson uses chemical and biophysical tools to understand and tune the activity of molecular chaperone proteins in protein misfolding diseases. Thus, her research group will reveal the molecular underpinnings of molecular chaperone dysfunction in a broad array of disorders including Huntington’s disease and Parkinson’s disease. These tools and finding will be further developed to develop novel treatments for patients of these diseases.

Johnson earned her bachelor’s degree in biochemistry from Florida Agricultural and Mechanical University in 2013, and her PhD from the University of Michigan in 2018. Prior to MIT, Johnson completed postdoctoral research at the University of California at San Francisco.

Nicole Xike Nie is an isotope geo/cosmochemist using the chemical and isotopic compositions of extraterrestrial materials to understand the formation of our solar system. Her research is driven by fundamental questions about the origin and evolution of the early solar system. Leveraging geochemical methods, she wants to understand questions such as why all planetary bodies are depleted of volatile elements when their building block materials aren’t, and why the Earth’s chemical signatures are distinct from other planetary bodies.

Nie joins MIT as an assistant professor in the Department of Earth, Atmospheric and Planetary Sciences. Nie received a BS in geology from China University of Geosciences in 2010, an MS in geochemistry from Chinese Academy of Sciences in 2013, and a PhD in geo/cosmochemistry from the University of Chicago in 2019. After graduating she was a Carnegie Postdoc Fellow at Carnegie Institution for Science and a postdoc researcher at Caltech.

Tristan Ozuch works in the field of geometric analysis and focuses on Einstein manifolds and Ricci flows. His work has shed light on the moduli space of Einstein metrics in four dimensions, addressing questions that have lingered since the 1980s. These questions originated from the systematic study of Einstein's equations and their degenerations since the 1970s, in both physics and mathematics.

After receiving a bachelor's degree, master's degree, and PhD from École Normale Supérieure, Tristan Ozuch joined MIT as a C.L.E. Moore Instructor of Mathematics. He continues in the Department of Mathematics as an assistant professor.

Climate scientist Talia Tamarin-Brodsky’s research is driven by questions on the interface between weather and climate. In her work, Tamarin-Brodsky combines theory, computational methods, and observational data to study Earth’s climate and weather and how they respond to climate change. Her interests include atmospheric dynamics, temperature variability, weather and climate extremes, and subseasonal-to-seasonal predictability. For example, she studies how nonlinear wave breaking events in the upper atmosphere influence surface weather and extremes, and the mechanisms shaping the spatial distribution of Earth’s near-surface temperature.

Tamarin-Brodsky received a bachelor’s degree in mathematics and geophysics as well as a master’s in physics from Tel Aviv University, Israel, before earning her PhD from the Weizmann Institute. She completed a postdoctoral project at the University of Reading, U.K., and a postdoctoral fellowship at Tel Aviv University. She joins the Department of Earth, Atmospheric and Planetary Studies as an assistant professor.

John Urschel PhD ’21 is a mathematician focused on matrix analysis and computations, with an emphasis on theoretical results and provable guarantees for practical problems. His research interests include numerical linear algebra, spectral graph theory, and topics in theoretical machine learning.

Urschel earned bachelor’s and master’s degrees in mathematics from Pennsylvania State University, then completed a PhD in mathematics at MIT in 2021. He was a member of the Institute for Advanced Study and a junior fellow at Harvard University before returning to MIT as an assistant professor of mathematics this fall.


Mon, 25 Sep 2023 11:00:00 -0400

New qubit circuit enables quantum operations with higher accuracy
Posted on Monday September 25, 2023

Category : Research

Author : Adam Zewe | MIT News

The advance brings quantum error correction a step closer to reality.

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In the future, quantum computers may be able to solve problems that are far too complex for today’s most powerful supercomputers. To realize this promise, quantum versions of error correction codes must be able to account for computational errors faster than they occur.

However, today’s quantum computers are not yet robust enough to realize such error correction at commercially relevant scales.

On the way to overcoming this roadblock, MIT researchers demonstrated a novel superconducting qubit architecture that can perform operations between qubits — the building blocks of a quantum computer — with much greater accuracy than scientists have previously been able to achieve.

They utilize a relatively new type of superconducting qubit, known as fluxonium, which can have a lifespan that is much longer than more commonly used superconducting qubits.

Their architecture involves a special coupling element between two fluxonium qubits that enables them to perform logical operations, known as gates, in a highly accurate manner. It suppresses a type of unwanted background interaction that can introduce errors into quantum operations.

This approach enabled two-qubit gates that exceeded 99.9 percent accuracy and single-qubit gates with 99.99 percent accuracy. In addition, the researchers implemented this architecture on a chip using an extensible fabrication process.  

“Building a large-scale quantum computer starts with robust qubits and gates. We showed a highly promising two-qubit system and laid out its many advantages for scaling. Our next step is to increase the number of qubits,” says Leon Ding PhD ’23, who was a physics graduate student in the Engineering Quantum Systems (EQuS) group and is the lead author of a paper on this architecture.

Ding wrote the paper with Max Hays, an EQuS postdoc; Youngkyu Sung PhD ’22; Bharath Kannan PhD ’22, who is now CEO of Atlantic Quantum; Kyle Serniak, a staff scientist and team lead at MIT Lincoln Laboratory; and senior author William D. Oliver, the Henry Ellis Warren professor of electrical engineering and computer science and of physics, director of the Center for Quantum Engineering, leader of EQuS, and associate director of the Research Laboratory of Electronics; as well as others at MIT and MIT Lincoln Laboratory. The research appears today in Physical Review X.

A new take on the fluxonium qubit

In a classical computer, gates are logical operations performed on bits (a series of 1s and 0s) that enable computation. Gates in quantum computing can be thought of in the same way: A single qubit gate is a logical operation on one qubit, while a two-qubit gate is an operation that depends on the states of two connected qubits.

Fidelity measures the accuracy of quantum operations performed on these gates. Gates with the highest possible fidelities are essential because quantum errors accumulate exponentially. With billions of quantum operations occurring in a large-scale system, a seemingly small amount of error can quickly cause the entire system to fail.

In practice, one would use error-correcting codes to achieve such low error rates. However, there is a “fidelity threshold” the operations must surpass to implement these codes. Furthermore, pushing the fidelities far beyond this threshold reduces the overhead needed to implement error correcting codes.

For more than a decade, researchers have primarily used transmon qubits in their efforts to build quantum computers. Another type of superconducting qubit, known as a fluxonium qubit, originated more recently. Fluxonium qubits have been shown to have longer lifespans, or coherence times, than transmon qubits.

Coherence time is a measure of how long a qubit can perform operations or run algorithms before all the information in the qubit is lost.

“The longer a qubit lives, the higher fidelity the operations it tends to promote. These two numbers are tied together. But it has been unclear, even when fluxonium qubits themselves perform quite well, if you can perform good gates on them,” Ding says.

For the first time, Ding and his collaborators found a way to use these longer-lived qubits in an architecture that can support extremely robust, high-fidelity gates. In their architecture, the fluxonium qubits were able to achieve coherence times of more than a millisecond, about 10 times longer than traditional transmon qubits.

“Over the last couple of years, there have been several demonstrations of fluxonium outperforming transmons on the single-qubit level,” says Hays. “Our work shows that this performance boost can be extended to interactions between qubits as well.”

The fluxonium qubits were developed in a close collaboration with MIT Lincoln Laboratory, (MIT-LL), which has expertise in the design and fabrication of extensible superconducting qubit technologies.

“This experiment was exemplary of what we call the ‘one-team model’: the close collaboration between the EQuS group and the superconducting qubit team at MIT-LL,” says Serniak. “It’s worth highlighting here specifically the contribution of fabrication team at MIT-LL — they developed the capability to construct dense arrays of more than 100 Josephson junctions specifically for fluxoniums and other new qubit circuits.”

A stronger connection

Their novel architecture involves a circuit that has two fluxonium qubits on either end, with a tunable transmon coupler in the middle to join them together. This fluxonium-transmon-fluxonium (FTF) architecture enables a stronger coupling than methods that directly connect two fluxonium qubits.

FTF also minimizes unwanted interactions that occur in the background during quantum operations. Typically, stronger couplings between qubits can lead to more of this persistent background noise, known as static ZZ interactions. But the FTF architecture remedies this problem.

The ability to suppress these unwanted interactions and the longer coherence times of fluxonium qubits are two factors that enabled the researchers to demonstrate single-qubit gate fidelity of 99.99 percent and two-qubit gate fidelity of 99.9 percent.

These gate fidelities are well above the threshold needed for certain common error correcting codes, and should enable error detection in larger-scale systems.

“Quantum error correction builds system resilience through redundancy. By adding more qubits, we can improve overall system performance, provided the qubits are individually ‘good enough.’ Think of trying to perform a task with a room full of kindergartners. That’s a lot of chaos, and adding more kindergartners won’t make it better,” Oliver explains. “However, several mature graduate students working together leads to performance that exceeds any one of the individuals — that’s the threshold concept. While there is still much to do to build an extensible quantum computer, it starts with having high-quality quantum operations that are well above threshold.”

Building off these results, Ding, Sung, Kannan, Oliver, and others recently founded a quantum computing startup, Atlantic Quantum. The company seeks to use fluxonium qubits to build a viable quantum computer for commercial and industrial applications.

“These results are immediately applicable and could change the state of the entire field. This shows the community that there is an alternate path forward. We strongly believe that this architecture, or something like this using fluxonium qubits, shows great promise in terms of actually building a useful, fault-tolerant quantum computer,” Kannan says.

While such a computer is still probably 10 years away, this research is an important step in the right direction, he adds. Next, the researchers plan to demonstrate the advantages of the FTF architecture in systems with more than two connected qubits.

“This work pioneers a new architecture for coupling two fluxonium qubits. The achieved gate fidelities are not only the best on record for fluxonium, but also on par with those of transmons, the currently dominating qubit. More importantly, the architecture also offers a high degree of flexibility in parameter selection, a feature essential for scaling up to a multi-qubit fluxonium processor,” says Chunqing Deng, head of the experimental quantum team at the Quantum Laboratory of DAMO Academy, Alibaba’s global research institution, who was not involved with this work. “For those of us who believe that fluxonium is a fundamentally better qubit than transmon, this work is an exciting and affirming milestone. It will galvanize not just the development of fluxonium processors but also more generally that for qubits alternative to transmons.”

This work was funded, in part, by the U.S. Army Research Office, the U.S. Undersecretary of Defense for Research and Engineering, an IBM PhD fellowship, the Korea Foundation for Advance Studies, and the U.S. National Defense Science and Engineering Graduate Fellowship Program.


Mon, 18 Sep 2023 14:30:00 -0400

Mikhail Ivanov wins 2024 New Horizons in Physics Breakthrough Prize
Posted on Monday September 18, 2023

Category : Faculty

Author : Sandi Miller | Department of Physics

MIT assistant professor of physics shares award for understanding the large-scale structure of the universe.

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Assistant professor of physics Mikhail Ivanov will receive the 2024 New Horizons in Physics Prize, which he will share with Marko Simonović from the National Institute for Nuclear Physics (INFN) at the University of Florence, and Oliver Philcox from Columbia University and the Simons Foundation.

The New Horizons Prize, which is given to promising early-career physicists and mathematicians making strides in their research fields, recognizes Ivanov, Simonovic, and Philcox “for contributions to our understanding of the large-scale structure of the universe and the development of new tools to extract fundamental physics from galaxy surveys.”

“It is a great honor for me to receive this award, and I'm deeply grateful to the selection committee for this privilege,” says Ivanov. “It is a symbol of academic recognition, but also a symbol of responsibility. It means I have an obligation to continue carrying out quality research and mentoring the younger generation of physicists.”

The three researchers were recognized for their study of the structure of the cosmos at the galactic scale, and for finding ways to use that knowledge to bring fresh insights to fundamental physics. This large-scale structure of the universe has the potential to become a new gold mine of cosmological information that could provide crucial insights into the nature of dark matter, dark energy, and the early universe, says Ivanov.

They created theoretical and practical tools for cosmological parameter estimation from galaxy clustering data to produce novel measurements of cosmological parameters and constraints on physics beyond the standard cosmological model from the BOSS (Baryon Oscillation Spectroscopic Survey) and eBOSS surveys. These results set the stage for new studies of fundamental physics with upcoming high-precision galaxy clustering data. 

Ivanov is a researcher in MIT's Center for Theoretical Physics (CTP), a division of the Laboratory for Nuclear Science. Ivanov’s research is at the interface of theoretical physics and data analysis, bridging state-of-the-art theoretical ideas with observational data. He seeks to use Effective Field Theory in combination with astrophysical data in order to resolve fundamental challenges of modern physics, such as the nature of dark matter, dark energy, inflation, and gravity.

“Professor Ivanov joined our department this fall, and we are delighted and proud that he has received this important recognition of his work,” says physics department head Deepto Chakrabarty.

Under the supervision of Sergey Sibiryakov in 2019, Ivanov received his PhD from the École Polytechnique fédérale de Lausanne and spent a year at the Institute for Advanced Study in Princeton, New Jersey, as a fellow of the Swiss National Science Foundation. He was a postdoc at New York University and a NASA Einstein Fellow at the Institute for Advanced Study, and joined the CTP as an assistant professor in July.

Other recognitions include the 2021-23 NASA Hubble Fellowship Program Einstein Fellowship, the 2021 Second Buchalter Cosmology Prize, the 2019 EPFL PhD Distinction prize for “an outstanding thesis in physics,” and a 2018-19 Swiss National Science Foundation Mobility Fellowship.

The trio are among 12 early-career physicists and mathematicians sharing six $100,000 New Horizons in Physics Prizes.

Founded by a group of Silicon Valley entrepreneurs, the Breakthrough Prizes recognize the world’s top scientists in life sciences, fundamental physics, and mathematics. The laureates are to be honored at the 10th annual Breakthrough Prize ceremony in Los Angeles on April 13, 2024.


Wed, 06 Sep 2023 17:15:00 -0400

Canceling noise to improve quantum devices
Posted on Wednesday September 06, 2023

Category : Research

Author : Peter Reuell | Department of Nuclear Science and Engineering

MIT researchers develop a protocol to extend the life of quantum coherence.

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For years, researchers have tried various ways to coax quantum bits — or qubits, the basic building blocks of quantum computers — to remain in their quantum state for ever-longer times, a key step in creating devices like quantum sensors, gyroscopes, and memories.

A team of physicists from MIT have taken an important step forward in that quest, and to do it, they borrowed a concept from an unlikely source — noise-canceling headphones.

Led by Ju Li, the Battelle Energy Alliance Professor in Nuclear Engineering and professor of materials science and engineering, and Paola Cappellaro, the Ford Professor of Engineering in the Department of Nuclear Science and Engineering and Research Laboratory of Electronics, and a professor of physics, the team described a method to achieve a 20-fold increase in the coherence times for nuclear-spin qubits. The work is described in a paper published in Physical Review Letters. The first author of the study is Guoqing Wang PhD '23, a recent doctoral student in Cappellaro’s lab who is now a postdoc at MIT.

“This is one of the main problems in quantum information,” Li says. “Nuclear spin (ensembles) are very attractive platforms for quantum sensors, gyroscopes, and quantum memory, (but) they have coherence times on the order of 150 microseconds in the presence of electronic spins … and then the information just disappears. What we have shown is that, if we can understand the interactions, or the noise, in these systems, we can actually do much better.”

Extending coherence with an “unbalanced echo”

In much the same way noise-cancelling headphones use specific sound frequencies to filter out surrounding noise, the team developed an approach they dubbed an “unbalanced echo” to extend the system’s coherence time.

By characterizing how a particular source of noise — in this case, heat — affected nuclear quadrupole interactions in the system, the team was able to use that same source of noise to offset the nuclear-electron interactions, extending coherence times from 150 microseconds to as long as 3 milliseconds.

Those improvements, however, may only be the beginning. More advances may be possible, says Wang, first author of the study who came up with the protection protocol, as they explore other possible sources of noise.

“In theory, we could even improve it to hundreds or even thousands of times longer. But in practice there may be other sources of noise in the system, and what we’ve shown is that if we can describe them, we can cancel them.”

The paper will have “significant impact” on future work on quantum devices, says Dmitry Budker, leader of the Matter-Antimatter Section of the Helmholtz Institute Mainz, professor at the Johannes Gutenberg University and at the University of California at Berkeley, who was not involved in the research.

“(This group is) the world leaders in the field of quantum sensing,” he says. “They constantly invent new approaches to stimulate developments in this booming field. In this work, they demonstrate a practical way to stretch nuclear coherence time by an order of magnitude with an ingenious spin-echo technique that should be relatively straightforward to implement in applications.”

Cornell University professor of applied and engineering physics Gregory Fuchs calls the work “innovative and impactful.”  

“This (work) is important because although nuclear spin can in principle have much longer coherence lifetimes than the electron spins native to the NV centers, it has been challenging for anyone to observe long-lived nuclear spin ensembles in diamond NV center experiments,” he says. “What Professor Cappellaro and her students have shown is a rather unexpected strategy for doing that. This approach can be highly impactful for applications of nuclear spin ensembles, such as for rotation sensing (a gyroscope).”

Building a sensor using “10 billion clocks”

The experiments and calculations described in the paper deal with a large ensemble — approximately 10 billion — of atomic-scale impurities in diamond known as nitrogen vacancy centers, or NV centers, each of which exists in a specific quantum spin state for the nitrogen-14 nucleus, as well as a localized electron nearby.

While they have long been identified as an ideal candidate for quantum sensors, gyroscopes, memories and more, the challenge, Wang explains, lay in working out a way to get large ensembles of NV centers to work together.

“If you think of each spin as being like a clock, these 10 billion clocks are all slightly different … and you cannot measure them all individually,” Wang says. “What we see is when you prepare all these clocks, they are initially in sync with each other at the beginning, but after some time, they completely lose their phase. We call this their de-phasing time.

“The goal is to use a billion clocks but achieve the same de-phasing time as a single clock,” he continues. “That allows you to get enhancements from measuring multiple clocks, but at the same time you preserve the phase coherence, so you don’t lose your quantum information as fast.”

The underlying theory of temperature heterogeneity induced de-phasing, which relates to the materials properties, was first outlined in March by a team of researchers that included Li, Cappellaro, Wang, and other MIT graduate students. That paper, published in the Journal of Physical Chemistry Letters, described a theoretical approach for calculating how temperature and strain affect different types of interactions which can lead to decoherence.

The first, known as nuclear quadrupole interaction, occurs because the nitrogen nucleus acts as an imperfect nuclear dipole — essentially a subatomic magnet. Because the nucleus is not perfectly spherical, Wang explains, it deforms, disrupting the dipole, which effectively interacts with itself. Similarly, hyperfine interaction is the result of the nucleus magnetic dipole interacting with the nearby electron magnetic dipole. Both of these two types of interactions can vary spatiotemporally, and when considering an ensemble of nuclear spin qubits, de-phasing can happen since “clocks at different locations can get different phases.”

Based on their earlier paper, the team theorized that, if they could characterize how those interactions were affected by heat, they would be able to offset the effect and extend coherence times for the system.

“Temperature or strain affects both of those interactions,” Wang says. “The theory we described predicted how temperature or strain would affect the quadrupole and hyperfine, and then the unbalanced echo we developed in this work is essentially canceling out the spectral drift due to one physical interaction using another different physical interaction, utilizing their correlation induced by the same noise.”

The key novelty of this work, compared to existing spin echo techniques commonly used in the quantum community, is to use different interaction noises to cancel each other such that the noises to be canceled can be highly selective. “What’s exciting, though, is that we can use this system in other ways,” he continues. “So, we could use this to sense temperature or strain field spatiotemporal heterogeneity. This could be quite good for something like biological systems, where even a very minute temperature shift could have significant effects.”

Additional applications

Those applications, Wang says, barely scratch the surface of the system’s potential applications.

“This system could also be used to examine electrical currents in electric vehicles, and because it can measure strain fields, it could be used for non-destructive structural health evaluation,” Li says. “You could imagine a bridge, if it had these sensors on it, we could understand what type of strain it’s experiencing. In fact, diamond sensors are already used to measure temperature distribution on the surface of materials, because it can be a very sensitive, high spatial resolution sensor.”

Another application, Li says, may be in biology. Researchers have previously demonstrated that the use of quantum sensors to map neuronal activity from electromagnetic fields could offer potential improvements, enabling a better understanding of some biological processes.

The system described in the paper could also represent a significant leap forward for quantum memory.

While there are some existing approaches to extending the coherence time of qubits for use in quantum memory, those processes are complex, and typically involve “flipping” — or reversing the spin — of the NV centers. While that process works to reverse the spectral drift that causes decoherence, it also leads to the loss of whatever information was encoded in the system.

By eliminating the need to reverse the spin, the new system not only extends the coherence time of the qubits, but prevents the loss of data, a key step forward for quantum computing.

Going forward, the team plans to investigate additional sources of noise — like fluctuating electrical field interference — in the system with the goal of counteracting them to further increase coherence time.

“Now that we’ve achieved a 20-fold improvement, we’re looking at how we can improve it even more, because intrinsically, this unbalanced echo can achieve an almost infinite improvement,” Li says. “We are also looking at how we can apply this system to the creation of a quantum gyroscope, because coherence time is just one key parameter to building a gyroscope, and there are other parameters we’re trying to optimize to (understand) the sensitivity we can achieve compared to previous techniques.”

This work was supported in part by the Defense Advanced Research Projects Agency DRINQS program, the National Science Foundation, and the Defense Threat Reduction Agency Interaction of Ionizing Radiation with Matter University Research Alliance. The calculations in this work were performed in part on the Texas Advanced Computing Center and the MIT engaging cluster.


Tue, 05 Sep 2023 16:10:00 -0400

Uncovering how biomes respond to climate change
Posted on Tuesday September 05, 2023

Category : Staff

Author : Stephanie Martinovich | Department of Civil and Environmental Engineering

Postdoc Leila Mirzagholi uses her background in physics to understand global warming's impact on the terrestrial carbon cycle.

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Before Leila Mirzagholi arrived at MIT’s Department of Civil and Environmental Engineering (CEE) to begin her postdoc appointment, she had spent most of her time in academia building cosmological models to detect properties of gravitational waves in the cosmos.

But as a member of Assistant Professor César Terrer’s lab in CEE, Mirzagholi uses her physics and mathematical background to improve our understanding of the different factors that influence how much carbon land ecosystems can store under climate change.

“What was always important to me was thinking about how to solve a problem and putting all the pieces together and building something from scratch,” Mirzagholi says, adding this was one of the reasons that it was possible for her to switch fields — and what drives her today as a climate scientist.

Growing up in Iran, Mirzagholi knew she wanted to be a scientist from an early age. As a kid, she became captivated by physics, spending most of her free time in a local cultural center that hosted science events. “I remember in that center there was an observatory that held observational tours and it drew me into science,” says Mirzgholi. She also remembers a time when she was a kid watching the science fiction film “Contact” that introduces a female scientist character who finds evidence of extraterrestrial life and builds a spaceship to make first contact: “After that movie my mind was set on pursuing astrophysics.”

With the encouragement of her parents to develop a strong mathematical background before pursuing physics, she earned a bachelor’s degree in mathematics from Tehran University. Then she completed a one-year master class in mathematics at Utrecht University before completing her PhD in theoretical physics at Max Planck Institute for Astrophysics in Munich. There, Mirzgholi's thesis focused on developing cosmological models with a focus on phenomenological aspects like propagation of gravitational waves on the cosmic microwave background.

Midway through her PhD, Mirzgholi became discouraged with building models to explain the dynamics of the early universe because there is little new data. “It starts to get personal and becomes a game of: ‘Is it my model or your model?’” she explains. She grew frustrated not knowing when the models she'd built would ever be tested.

It was at this time that Mirzgholi started reading more about the topics of climate change and climate science. “I was really motivated by the problems and the nature of the problems, especially to make global terrestrial ecology more quantitative,” she says. She also liked the idea of contributing to a global problem that we are all facing. She started to think, “maybe I can do my part, I can work on research beneficial for society and the planet.”

She made the switch following her PhD and started as a postdoc in the Crowther Lab at ETH Zurich, working on understanding the effects of environmental changes on global vegetation activity. After a stint at ETH, where her colleagues collaborated on projects with the Terrer Lab, she relocated to Cambridge, Massachusetts, to join the lab and CEE.

Her latest article in Science, which was published in July and co-authored by researchers from ETH, shows how global warming affects the timing of autumn leaf senescence. “It’s important to understand the length of the growing season, and how much the forest or other biomes will have the capacity to take in carbon from the atmosphere.” Using remote sensing data, she was able to understand when the growing season will end under a warming climate. “We distinguish two dates — when autumn is onsetting and the leaves are starting to turn yellow, versus when the leaves are 50 percent yellow — to represent the progression of leaf senescence,” she says.

In the context of rising temperature, when the warming is happening plays a crucial role. If warming temperatures happen before the summer solstice, it triggers trees to begin their seasonal cycles faster, leading to reduced photosynthesis, ending in an earlier autumn. On the other hand, if the warming happens after the summer solstice, it delays the discoloration process, making autumn last longer. “For every degree Celsius of pre-solstice warming, the onset of leaf senescence advances by 1.9 days, while each degree Celsius of post-solstice warming delays the senescence process by 2.6 days,” she explains. Understanding the timing of autumn leaf senescence is essential in efforts to predict carbon storage capacity when modeling global carbon cycles.

Another problem she’s working on in the Terrer Lab is discovering how deforestation is changing our local climate. How much is it cooling or warming the temperature, and how is the hydrological cycle changing because of deforestation? Investigating these questions will give insight into how much we can depend on natural solutions for carbon uptake to help mitigate climate change. “Quantitatively, we want to put a number to the amount of carbon uptake from various natural solutions, as opposed to other solutions,” she says.

With year-and-a-half left in her postdoc appointment, Mirzagholi has begun considering her next career steps. She likes the idea of applying to climate scientist jobs in industry or national labs, as well as tenure track faculty positions. Whether she pursues a career in academia or industry, Mirzagholi aims to continue conducting fundamental climate science research. Her multidisciplinary background in physics, mathematics, and climate science has given her a multifaceted perspective, which she applies to every research problem.

“Looking back, I’m grateful for all my educational experiences from spending time in the cultural center as a kid, my background in physics, the support from colleagues at the Crowther lab at ETH who facilitated my transition from physics to ecology, and now working at MIT alongside Professor Terrer, because it’s shaped my career path and the researcher I am today.”


Fri, 01 Sep 2023 11:30:00 -0400

Fast-tracking fusion energy’s arrival with AI and accessibility
Posted on Friday September 01, 2023

Category : Research

Author : Julianna Mullen | Plasma Science and Fusion Center

MIT Plasma Science and Fusion Center will receive DoE support to improve access to fusion data and increase workforce diversity.

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As the impacts of climate change continue to grow, so does interest in fusion’s potential as a clean energy source. While fusion reactions have been studied in laboratories since the 1930s, there are still many critical questions scientists must answer to make fusion power a reality, and time is of the essence. As part of their strategy to accelerate fusion energy’s arrival and reach carbon neutrality by 2050, the U.S. Department of Energy (DoE) has announced new funding for a project led by researchers at MIT’s Plasma Science and Fusion Center (PSFC) and four collaborating institutions.

Cristina Rea, a research scientist and group leader at the PSFC, will serve as the primary investigator for the newly funded three-year collaboration to pilot the integration of fusion data into a system that can be read by AI-powered tools. The PSFC, together with scientists from William & Mary, the University of Wisconsin at Madison, Auburn University, and the nonprofit HDF Group, plan to create a holistic fusion data platform, the elements of which could offer unprecedented access for researchers, especially underrepresented students. The project aims to encourage diverse participation in fusion and data science, both in academia and the workforce, through outreach programs led by the group’s co-investigators, of whom four out of five are women. 

The DoE’s award, part of a $29 million funding package for seven projects across 19 institutions, will support the group’s efforts to distribute data produced by fusion devices like the PSFC’s Alcator C-Mod, a donut-shaped “tokamak” that utilized powerful magnets to control and confine fusion reactions. Alcator C-Mod operated from 1991 to 2016 and its data are still being studied, thanks in part to the PSFC’s commitment to the free exchange of knowledge.

Currently, there are nearly 50 public experimental magnetic confinement-type fusion devices; however, both historical and current data from these devices can be difficult to access. Some fusion databases require signing user agreements, and not all data are catalogued and organized the same way. Moreover, it can be difficult to leverage machine learning, a class of AI tools, for data analysis and to enable scientific discovery without time-consuming data reorganization. The result is fewer scientists working on fusion, greater barriers to discovery, and a bottleneck in harnessing AI to accelerate progress.

The project’s proposed data platform addresses technical barriers by being FAIR — Findable, Interoperable, Accessible, Reusable — and by adhering to UNESCO’s Open Science (OS) recommendations to improve the transparency and inclusivity of science; all of the researchers’ deliverables will adhere to FAIR and OS principles, as required by the DoE. The platform’s databases will be built using MDSplusML, an upgraded version of the MDSplus open-source software developed by PSFC researchers in the 1980s to catalogue the results of Alcator C-Mod’s experiments. Today, nearly 40 fusion research institutes use MDSplus to store and provide external access to their fusion data. The release of MDSplusML aims to continue that legacy of open collaboration.

The researchers intend to address barriers to participation for women and disadvantaged groups not only by improving general access to fusion data, but also through a subsidized summer school that will focus on topics at the intersection of fusion and machine learning, which will be held at William & Mary for the next three years.

Of the importance of their research, Rea says, “This project is about responding to the fusion community’s needs and setting ourselves up for success. Scientific advancements in fusion are enabled via multidisciplinary collaboration and cross-pollination, so accessibility is absolutely essential. I think we all understand now that diverse communities have more diverse ideas, and they allow faster problem-solving.”

The collaboration’s work also aligns with vital areas of research identified in the International Atomic Energy Agency’s “AI for Fusion” Coordinated Research Project (CRP). Rea was selected as the technical coordinator for the IAEA’s CRP emphasizing community engagement and knowledge access to accelerate fusion research and development. In a letter of support written for the group’s proposed project, the IAEA stated that, “the work [the researchers] will carry out […] will be beneficial not only to our CRP but also to the international fusion community in large.”

PSFC Director and Hitachi America Professor of Engineering Dennis Whyte adds, “I am thrilled to see PSFC and our collaborators be at the forefront of applying new AI tools while simultaneously encouraging and enabling extraction of critical data from our experiments.”

“Having the opportunity to lead such an important project is extremely meaningful, and I feel a responsibility to show that women are leaders in STEM,” says Rea. “We have an incredible team, strongly motivated to improve our fusion ecosystem and to contribute to making fusion energy a reality.”


Thu, 31 Aug 2023 13:30:00 -0400

3 Questions: A bigger, better space-ripple detector
Posted on Thursday August 31, 2023

Category : Interview

Author : Jennifer Chu | MIT News

The MIT-led Cosmic Explorer project aims to detect gravitational waves from the earliest universe.

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The search for space-shaking ripples in the universe just got a big boost. An MIT-led effort to build a bigger, better gravitational-wave detector will receive $9 million dollars over the next three years from the National Science Foundation. The funding infusion will support the design phase for Cosmic Explorer — a next-generation gravitational-wave observatory that is expected to pick up ripples in space-time from as far back as the early universe. To do so, the observatory’s detectors are planned to span the length of a small city.

The observatory’s conceptual design takes after the detectors of LIGO — the Laser Interferometer Gravitational-wave Observatory that is operated by MIT and Caltech. LIGO “listens” for gravitational waves by measuring the timing of two lasers that travel from the same point, down two separate tunnels, and back again. Any difference in their arrival times can be a signal that a gravitational wave passed through the L-shaped detector. LIGO includes two twin detectors, sited in different locations in the United States. A similar set of detectors, Virgo, operates in Italy, along with a third, KAGRA, in Japan.

Together, this existing network of detectors picks up ripples from gravitational-wave sources, such as merging black holes and neutron stars, every few days. Cosmic Explorer, scientists believe, should bump that rate up to a signal every few minutes. The science coming out of these detections could provide answers to some of the biggest questions in cosmology.

MIT News checked in with Cosmic Explorer’s executive director, Matthew Evans, who is a professor of physics at MIT, and co-principal investigator Salvatore Vitale, associate professor of physics at MIT, about what they hope to hear from the earliest universe.

Q: Walk us through the general idea for Cosmic Explorer — what will make it a “next-generation” detector of gravitational waves?

Evans: Cosmic Explorer is in some sense a giant LIGO. The LIGO detectors are four kilometers long for each arm, and Cosmic Explorer will be 40 kilometers on a side, so 10 times larger. And the signal that we get from a gravitational wave is essentially proportional to the size of our detector, and that’s why these things are so big.

Bigger is better, up to a point. At some point, you’ve matched the length of the detector to the wavelength of the incoming gravitational waves. And then, if you continue making it bigger, there’s really diminishing returns in terms of scientific output. It’s also hard to find sites to build that large of a detector. When you get too big, the curvature of the Earth starts to become an issue because the detector’s laser beam has to travel in a straight line, and that’s less possible when a detector is so large that it has to curve with the Earth.

In terms of looking for possible sites, fortunately now, as opposed to in the 1980s when sites were being looked at for LIGO, there’s a lot of public data that’s available digitally. So we have already first versions of algorithmic searches that can search the U.S. for potential candidate sites. We’re looking for places which are kind of flat but also a little bowl-shaped in terms of altitude because that would avoid some excavation. And we’re looking for places that are not in the middle of cities or lakes, or in the mountains, and that aren’t too far from populated regions so that we could imagine getting scientists in and out. Our first go-around shows there are some potential candidates, especially in the western half of the U.S.

We see Cosmic Explorer as “next-generation” in the sense that it will replace existing observatories. If we were to build two Cosmic Explorer observatories in the U.S., which is our reference concept, then we would presumably shut down the two LIGO observatories. That’s probably mid-2030s, depending on how funding goes. So, it’s still a ways in the future. But we believe it would change the name of the game in terms of the science we can do.

Q: And what might that science be? What new things could you see, and what big questions could it answer?

Vitale: It will allow us to see sources that are farther away. And by sources, I mean things that we are seeing today, such as black holes and neutron stars colliding. Now, with the sensitivity of LIGO, we can see sources in our backyard, cosmologically speaking — about one-and-a-half billion years ago. That seems far away, but compared to the size of the universe, which is about 13 to 14 billion years old, that’s pretty nearby. That means we are missing important steps of the history of the universe, one of which is “Cosmic Noon,” where most of the stars in the universe were formed. That’s when the universe was around 3 billion years old. It would be great to access sources which were formed around that time, because it would teach us a lot about how black holes and neutron stars come from stars.

Going beyond that, when the universe was about a billion years old, during the Epoch of Reionization — that’s when atoms were ionized and galaxies started to form — this is still too far for us to see. Cosmic Explorer would be sensitive to the mergers of black holes and neutron stars up to those distances, and even farther than that.

We’ll also be able to see sources in a much clearer and louder way. Today, LIGO might detect something with a signal-to-noise ratio of 30, where it’s pretty loud but hard to characterize. That same signal, coming through Cosmic Explorer, would have a signal-to-noise of 3,000. So, anything that requires really sensitive measurements, like testing if Einstein’s relativity is correct, which now we can do but with large uncertainties — that would be a more precise test with Cosmic Explorer.

Finally, many measurements get better the more sources you have. We think Cosmic Explorer could detect hundreds of thousands of black hole binaries and up to a million neutron star mergers per year.

Evans: Being able to detect more sources lets you detect objects that are in the corners of parameter space, which you wouldn’t otherwise detect — like very large spins of the black hole, or very high mass ratios. If you have hundreds of thousands of sources, you can detect these oddballs.

Q: What’s next for the project going forward?

Evans: Over the next three years, we’ll be doing a full, top-down design, where we pick all the parameters of the instrument and include the infrastructure that goes around it, like the vacuum system, and we end up doing architectural designs for the buildings. And all of this needs to lead to a cost estimate which is fairly sound, both for the construction and the preliminary design. By the end of the next design phase we will have to have identified sites and have solid architectural and infrastructural designs done, and the design of the instrument will be at the nuts-and-bolts level.

The environment in which we’re doing this is one that includes other next-gen detectors in development, such as the space mission, LISA, being run by the European Space Agency, and expected to launch mid-2030s. There is also the Einstein Telescope in Europe. All these groups are colleagues rather than competitors, who we anticipate working with. In this field, you get farther by working together. It's kind of a global effort to build these next-generation gravitational wave detectors, and it’s global science.


Wed, 30 Aug 2023 00:00:00 -0400

Newly discovered planet has longest orbit yet detected by the TESS mission
Posted on Wednesday August 30, 2023

Category : Astronomy

Author : Jennifer Chu | MIT News

The frosty gas giant was discovered in a system that also hosts a warm Jupiter.

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Of the more than 5,000 planets known to exist beyond our solar system, most orbit their stars at surprisingly close range. More than 80 percent of confirmed exoplanets have orbits shorter than 50 days, placing these toasty worlds at least twice as close to their star as Mercury is to our sun — and some, even closer than that.

Astronomers are starting to get a general picture of these planets’ formation, evolution, and composition. But the picture is much fuzzier for planets with longer orbital periods. Far-out worlds, with months- to years-long orbits, are more difficult to detect, and their properties have therefore been trickier to discern.

Now, the list of long-period planets has gained two entries. Astronomers at MIT, the University of New Mexico, and elsewhere have discovered a rare system containing two long-period planets orbiting TOI-4600, a nearby star that is 815 light years from Earth.

The team discovered that the star hosts an inner planet with an orbit of 82 days, similar to that of Mercury, while a second outer planet circles every 482 days, placing it somewhere between the orbits of Earth and Mars.

The discovery was made using data from NASA’s Transiting Exoplanet Survey Satellite, or TESS — an MIT-led mission that monitors the nearest stars for signs of exoplanets. The new, farther planet has the longest period that TESS has detected to date. It is also one of the coldest, at about -117 degrees Fahrenheit, while the inner planet is a more temperate 170 degrees Fahrenheit.

Both planets are likely gas giants, similar to Jupiter and Saturn, though the composition of the inner planet may be more of a mix of gas and ice. The two planets bridge the gap between “hot Jupiters” — the toasty, short-orbit planets that make up the majority of exoplanet discoveries — and the much colder, longer-period gas giants in our solar system.

“These longer-period systems are a comparatively unexplored range,” says team member Katharine Hesse, a technical staff member at MIT’s Kavli Institute for Astrophysics and Space Research. “As we’re trying to see where our solar system falls in comparison to the other systems we’ve found out there, we really need these more edge-case examples to better understand that comparison. Because a lot of systems we have found don’t look anything like our solar system.”

Hesse and her colleagues, including lead author Ismael Mireles, a graduate student at the University of New Mexico (UNM), have published their results today in Astrophysical Journal Letters.

Patch work

TESS monitors the nearest stars for signs of exoplanets by pointing at a patch of the sky and continuously measuring the brightness of stars in that sector for 30 days, before swiveling to the next patch. Scientists use “pipelines,” or algorithmic searches, to comb through the measurements for dips in brightness that could have been caused by a planet passing in front of its star.

In 2020, one pipeline picked up a possible transit from a star in the northern sky, close to the constellation Draco. The star was categorized as TOI-4600 (a TESS Object of Interest). The initial transit was studied in detail by the TESS Single Transit Planet Candidate Working Group, a team of scientists at MIT, UNM, and elsewhere who look for signs of longer-period planets in single-transit events.

“For missions like TESS, where it only looks at each region of the sky for 30 days, you really need to stack up the number of observations to be able to get enough data to find planets with orbits longer than a month,” Hesse notes.

The group looked for the star in other sectors of TESS data and eventually identified three more transits, similar to the first. From these four events, the scientists were able to determine that the source was a planet — TOI-4600b — with a relatively long 82-day orbit. The team also picked up a fifth transit, though it was out of sync with the other signals. They wondered: Could the transit be from another star temporarily eclipsing the first? Or could it be a second orbiting planet?

Giants in the sky

In 2021, when Mireles joined the group, he took up where the team left off, looking for more observations from TESS that would explain the last, puzzling transit.

“With each sector of data that came down, I would look to see if there was a second transit, and in the first five sectors, there wasn’t,” Mireles recalls. “Then, in July of last year, we saw something.”

Actually, they saw two things: one transit that appeared in the same 82-day cycle, which further confirmed the existence of a long-orbiting planet; and a second transit, which was detected 964 days after the previous, out-of-sync transit. These last two transits were similar in depth, or the amount of light that was dimmed, suggesting that both were produced by a single object that was orbiting the star, either every 964 days, or every 482 days. After all, the team reasoned, TESS simply could have not been looking in the star’s direction to catch the planet crossing at the 482-day mark. The team used a model to simulate what a planet would look like with both orbital periods, and concluded that the 482-day orbit was more likely.

To further confirm they had identified two long-period planets, the researchers focused in on the star using multiple ground-based telescopes. These observations helped the team rule out false-positive scenarios, such as a second star eclipsing the main star. In the end, they concluded that the star indeed hosts two long-period planets: TOI-4600b, a warm, Jupiter-like giant; and TOI-4600c, a frosty, icier giant, and the longest-period planet detected by TESS to date.

“It’s relatively rare that we see two giant planets in a system,” Hesse offers. “We’re used to seeing hot Jupiters that are close in to their stars, and we usually don’t find companions to them, let alone giant companions. This system is a more unique configuration.”

The distance between the two planets, which is about the same as the space between Mercury and Mars, implies there could be other planets in the system.

“We want to see if there’s evidence for more planets,” Mireles says. “There’s definitely a lot of room for potential planets, either closer in, or further out. And we show that TESS is capable of finding both warm and cold Jupiters.”

 This research was supported, in part, by NASA.


Fri, 18 Aug 2023 14:00:00 -0400

Artificial intelligence for augmentation and productivity
Posted on Friday August 18, 2023

Category : Funding

Author : MIT Schwarzman College of Computing

The MIT Schwarzman College of Computing awards seed grants to seven interdisciplinary projects exploring AI-augmented management.

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The MIT Stephen A. Schwarzman College of Computing has awarded seed grants to seven projects that are exploring how artificial intelligence and human-computer interaction can be leveraged to enhance modern work spaces to achieve better management and higher productivity.

Funded by Andrew W. Houston ’05 and Dropbox Inc., the projects are intended to be interdisciplinary and bring together researchers from computing, social sciences, and management.

The seed grants can enable the project teams to conduct research that leads to bigger endeavors in this rapidly evolving area, as well as build community around questions related to AI-augmented management.

The seven selected projects and research leads include:

LLMex: Implementing Vannevar Bush’s Vision of the Memex Using Large Language Models,” led by Pattie Maes of the Media Lab and David Karger of the Department of Electrical Engineering and Computer Science (EECS) and the Computer Science and Artificial Intelligence Laboratory (CSAIL). Inspired by Vannevar Bush’s Memex, this project proposes to design, implement, and test the concept of memory prosthetics using large language models (LLMs). The AI-based system will intelligently help an individual keep track of vast amounts of information, accelerate productivity, and reduce errors by automatically recording their work actions and meetings, supporting retrieval based on metadata and vague descriptions, and suggesting relevant, personalized information proactively based on the user’s current focus and context.

Using AI Agents to Simulate Social Scenarios,” led by John Horton of the MIT Sloan School of Management and Jacob Andreas of EECS and CSAIL. This project imagines the ability to easily simulate policies, organizational arrangements, and communication tools with AI agents before implementation. Tapping into the capabilities of modern LLMs to serve as a computational model of humans makes this vision of social simulation more realistic, and potentially more predictive.

Human Expertise in the Age of AI: Can We Have Our Cake and Eat it Too?” led by Manish Raghavan of MIT Sloan and EECS, and Devavrat Shah of EECS and the Laboratory for Information and Decision Systems. Progress in machine learning, AI, and in algorithmic decision aids has raised the prospect that algorithms may complement human decision-making in a wide variety of settings. Rather than replacing human professionals, this project sees a future where AI and algorithmic decision aids play a role that is complementary to human expertise.

Implementing Generative AI in U.S. Hospitals,” led by Julie Shah of the Department of Aeronautics and Astronautics and CSAIL, Retsef Levi of MIT Sloan and the Operations Research Center, Kate Kellog of MIT Sloan, and Ben Armstrong of the Industrial Performance Center. In recent years, studies have linked a rise in burnout from doctors and nurses in the United States with increased administrative burdens associated with electronic health records and other technologies. This project aims to develop a holistic framework to study how generative AI technologies can both increase productivity for organizations and improve job quality for workers in health care settings.

Generative AI Augmented Software Tools to Democratize Programming,” led by Harold Abelson of EECS and CSAIL, Cynthia Breazeal of the Media Lab, and Eric Klopfer of the Comparative Media Studies/Writing. Progress in generative AI over the past year is fomenting an upheaval in assumptions about future careers in software and deprecating the role of coding. This project will stimulate a similar transformation in computing education for those who have no prior technical training by creating a software tool that could eliminate much of the need for learners to deal with code when creating applications.

Acquiring Expertise and Societal Productivity in a World of Artificial Intelligence,” led by David Atkin and Martin Beraja of the Department of Economics, and Danielle Li of MIT Sloan. Generative AI is thought to augment the capabilities of workers performing cognitive tasks. This project seeks to better understand how the arrival of AI technologies may impact skill acquisition and productivity, and to explore complementary policy interventions that will allow society to maximize the gains from such technologies.

AI Augmented Onboarding and Support,” led by Tim Kraska of EECS and CSAIL, and Christoph Paus of the Department of Physics and the Laboratory for Nuclear Science. While LLMs have made enormous leaps forward in recent years and are poised to fundamentally change the way students and professionals learn about new tools and systems, there is often a steep learning curve which people have to climb in order to make full use of the resource. To help mitigate the issue, this project proposes the development of new LLM-powered onboarding and support systems that will positively impact the way support teams operate and improve the user experience.


Tue, 15 Aug 2023 16:00:00 -0400

Simple superconducting device could dramatically cut energy use in computing, other applications
Posted on Tuesday August 15, 2023

Category : School of Science

Author : Elizabeth Thomson | Materials Research Laboratory

The ultrasmall “switch” could be easily scaled.

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MIT scientists and their colleagues have created a simple superconducting device that could transfer current through electronic devices much more efficiently than is possible today. As a result, the new diode, a kind of switch, could dramatically cut the amount of energy used in high-power computing systems, a major problem that is estimated to become much worse. Even though it is in the early stages of development, the diode is more than twice as efficient as similar ones reported by others. It could even be integral to emerging quantum computing technologies.

The work, which is reported in the July 13 online issue of Physical Review Letters, is also the subject of a news story in Physics Magazine.

“This paper showcases that the superconducting diode is an entirely solved problem from an engineering perspective,” says Philip Moll, director of the Max Planck Institute for the Structure and Dynamics of Matter in Germany. Moll was not involved in the work. “The beauty of [this] work is that [Moodera and colleagues] obtained record efficiencies without even trying [and] their structures are far from optimized yet.”

“Our engineering of a superconducting diode effect that is robust and can operate over a wide temperature range in simple systems can potentially open the door for novel technologies,” says Jagadeesh Moodera, leader of the current work and a senior research scientist in MIT’s Department of Physics. Moodera is also affiliated with the Materials Research Laboratory, the Francis Bitter Magnet Laboratory, and the Plasma Science and Fusion Center (PSFC).

The nanoscopic rectangular diode — about 1,000 times thinner than the diameter of a human hair — is easily scalable. Millions could be produced on a single silicon wafer.

Toward a superconducting switch

Diodes, devices that allow current to travel easily in one direction but not in the reverse, are ubiquitous in computing systems. Modern semiconductor computer chips contain billions of diode-like devices known as transistors. However, these devices can get very hot due to electrical resistance, requiring vast amounts of energy to cool the high-power systems in the data centers behind myriad modern technologies, including cloud computing. According to a 2018 news feature in Nature, these systems could use nearly 20 percent of the world’s power in 10 years.

As a result, work toward creating diodes made of superconductors has been a hot topic in condensed matter physics. That’s because superconductors transmit current with no resistance at all below a certain low temperature (the critical temperature), and are therefore much more efficient than their semiconducting cousins, which have noticeable energy loss in the form of heat.

Until now, however, other approaches to the problem have involved much more complicated physics. “The effect we found is due [in part] to a ubiquitous property of superconductors that can be realized in a very simple, straightforward manner. It just stares you in the face,” says Moodera.

Says Moll of the Max Planck Institute, “The work is an important counterpoint to the current fashion to associate superconducting diodes [with] exotic physics, such as finite-momentum pairing states. While in reality, a superconducting diode is a common and widespread phenomenon present in classical materials, as a result of certain broken symmetries.”

A somewhat serendipitous discovery

In 2020 Moodera and colleagues observed evidence of an exotic particle pair known as Majorana fermions. These particle pairs could lead to a new family of topological qubits, the building blocks of quantum computers. While pondering approaches to creating superconducting diodes, the team realized that the material platform they developed for the Majorana work might also be applied to the diode problem.

They were right. Using that general platform, they developed different iterations of superconducting diodes, each more efficient than the last. The first, for example, consisted of a nanoscopically thin layer of vanadium, a superconductor, which was patterned into a structure common to electronics (the Hall bar). When they applied a tiny magnetic field comparable to the Earth’s magnetic field, they saw the diode effect — a giant polarity dependence for current flow.

They then created another diode, this time layering a superconductor with a ferromagnet (a ferromagnetic insulator in their case), a material that produces its own tiny magnetic field. After applying a tiny magnetic field to magnetize the ferromagnet so that it produces its own field, they found an even bigger diode effect that was stable even after the original magnetic field was turned off.

Ubiquitous properties

The team went on to figure out what was happening.

In addition to transmitting current with no resistance, superconductors also have other, less well-known but just as ubiquitous properties. For example, they don’t like magnetic fields getting inside. When exposed to a tiny magnetic field, superconductors produce an internal supercurrent that induces its own magnetic flux that cancels the external field, thereby maintaining their superconducting state. This phenomenon, known as the Meissner screening effect, can be thought of as akin to our bodies’ immune system releasing antibodies to fight the infection of bacteria and other pathogens. This works, however, only up to some limit. Similarly, superconductors cannot entirely keep out large magnetic fields.

The diodes the team created make use of this universal Meissner screening effect. The tiny magnetic field they applied — either directly, or through the adjacent ferromagnetic layer — activates the material’s screening current mechanism for expelling the external magnetic field and maintaining superconductivity.

The team also found that another key factor in optimizing these superconductor diodes is tiny differences between the two sides, or edges, of the diode devices. These differences “create some sort of asymmetry in the way the magnetic field enters the superconductor,” Moodera says.

By engineering their own form of edges on diodes to optimize these differences — for example, one edge with sawtooth features, while the other edge not intentionally altered — the team found that they could increase the efficiency from 20 percent to more than 50 percent. This discovery opens the door for devices whose edges could be “tuned” for even higher efficiencies, Moodera says.

In sum, the team discovered that the edge asymmetries within superconducting diodes, the ubiquitous Meissner screening effect found in all superconductors, and a third property of superconductors known as vortex pinning all came together to produce the diode effect.

“It is fascinating to see how inconspicuous yet ubiquitous factors can create a significant effect in observing the diode effect,” says Yasen Hou, first author of the paper and a postdoc at the Francis Bitter Magnet Laboratory and the PSFC. “What’s more exciting is that [this work] provides a straightforward approach with huge potential to further improve the efficiency.”

Christoph Strunk is a professor at the University of Regensburg in Germany. Says Strunk, who was not involved in the research, “the present work demonstrates that the supercurrent in simple superconducting strips can become nonreciprocal. Moreover, when combined with a ferromagnetic insulator, the diode effect can even be maintained in the absence of an external magnetic field. The rectification direction can be programmed by the remnant magnetization of the magnetic layer, which may have high potential for future applications. The work is important and appealing both from the basic research and from the applications point of view.”

Teenage contributors

Moodera noted that the two researchers who created the engineered edges did so while still in high school during a summer at Moodera’s lab. They are Ourania Glezakou-Elbert of Richland, Washington, who will be going to Princeton University this fall, and Amith Varambally of Vestavia Hills, Alabama, who will be entering Caltech.

Says Varambally, “I didn't know what to expect when I set foot in Boston last summer, and certainly never expected to [be] a coauthor in a Physical Review Letters paper.

“Every day was exciting, whether I was reading dozens of papers to better understand the diode phenomena, or operating machinery to fabricate new diodes for study, or engaging in conversations with Ourania, Dr. Hou, and Dr. Moodera about our research.

“I am profoundly grateful to Dr. Moodera and Dr. Hou for providing me with the opportunity to work on such a fascinating project, and to Ourania for being a great research partner and friend.”

In addition to Moodera and Hou, corresponding authors of the paper are professors Patrick A. Lee of the MIT Department of Physics and Akashdeep Kamra of Autonomous University of Madrid. Other authors from MIT are Liang Fu and Margarita Davydova of the Department of Physics, and Hang Chi, Alessandro Lodesani, and Yingying Wu, all of the Francis Bitter Magnet Laboratory and the Plasma Science and Fusion Center. Chi is also affiliated with the U.S. Army CCDC Research Laboratory.

Authors also include Fabrizio Nichele, Markus F. Ritter, and Daniel Z. Haxwell of IBM Research Europe; Stefan Ilić of Materials Physics Center (CFM-MPC); and F. Sebastian Bergeret of CFM-MPC and Donostia International Physics Center.

This work was supported by the Air Force Office of Sponsored Research, the Office of Naval Research, the National Science Foundation, and the Army Research Office. Additional funders are the European Research Council, the European Union’s Horizon 2020 Research and Innovation Framework Programme, the Spanish Ministry of Science and Innovation, the A. v. Humboldt Foundation, and the Department of Energy’s Office of Basic Sciences.


Tue, 08 Aug 2023 17:00:00 -0400

Fourteen MIT School of Science professors receive tenure for 2022 and 2023
Posted on Tuesday August 08, 2023

Category : Faculty

Author : School of Science

Faculty members were recently granted tenure in the departments of Biology, Brain and Cognitive Sciences, Chemistry, EAPS, and Physics.

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In 2022, nine MIT faculty were granted tenure in the School of Science:

Gloria Choi examines the interaction of the immune system with the brain and the effects of that interaction on neurodevelopment, behavior, and mood. She also studies how social behaviors are regulated according to sensory stimuli, context, internal state, and physiological status, and how these factors modulate neural circuit function via a combinatorial code of classic neuromodulators and immune-derived cytokines. Choi joined the Department of Brain and Cognitive Sciences after a postdoc at Columbia University. She received her bachelor’s degree from the University of California at Berkeley, and her PhD from Caltech. Choi is also an investigator in The Picower Institute for Learning and Memory.

Nikta Fakhri develops experimental tools and conceptual frameworks to uncover laws governing fluctuations, order, and self-organization in active systems. Such frameworks provide powerful insight into dynamics of nonequilibrium living systems across scales, from the emergence of thermodynamic arrow of time to spatiotemporal organization of signaling protein patterns and discovery of odd elasticity. Fakhri joined the Department of Physics in 2015 following a postdoc at University of Göttingen. She completed her undergraduate degree at Sharif University of Technology and her PhD at Rice University.

Geobiologist Greg Fournier uses a combination of molecular phylogeny insights and geologic records to study major events in planetary history, with the hope of furthering our understanding of the co-evolution of life and environment. Recently, his team developed a new technique to analyze multiple gene evolutionary histories and estimated that photosynthesis evolved between 3.4 and 2.9 billion years ago. Fournier joined the Department of Earth, Atmospheric and Planetary Sciences in 2014 after working as a postdoc at the University of Connecticut and as a NASA Postdoctoral Program Fellow in MIT’s Department of Civil and Environmental Engineering. He earned his BA from Dartmouth College in 2001 and his PhD in genetics and genomics from the University of Connecticut in 2009.

Daniel Harlow researches black holes and cosmology, viewed through the lens of quantum gravity and quantum field theory. His work generates new insights into quantum information, quantum field theory, and gravity. Harlow joined the Department of Physics in 2017 following postdocs at Princeton University and Harvard University. He obtained a BA in physics and mathematics from Columbia University in 2006 and a PhD in physics from Stanford University in 2012. He is also a researcher in the Laboratory for Nuclear Science’s Center for Theoretical Physics.

A biophysicist, Gene-Wei Li studies how bacteria optimize the levels of proteins they produce at both mechanistic and systems levels. His lab focuses on design principles of transcription, translation, and RNA maturation. Li joined the Department of Biology in 2015 after completing a postdoc at the University of California at San Francisco. He earned an BS in physics from National Tsinghua University in 2004 and a PhD in physics from Harvard University in 2010.

Michael McDonald focuses on the evolution of galaxies and clusters of galaxies, and the role that environment plays in dictating this evolution. This research involves the discovery and study of the most distant assemblies of galaxies alongside analyses of the complex interplay between gas, galaxies, and black holes in the closest, most massive systems. McDonald joined the Department of Physics and the Kavli Institute for Astrophysics and Space Research in 2015 after three years as a Hubble Fellow, also at MIT. He obtained his BS and MS degrees in physics at Queen’s University, and his PhD in astronomy at the University of Maryland in College Park.

Gabriela Schlau-Cohen combines tools from chemistry, optics, biology, and microscopy to develop new approaches to probe dynamics. Her group focuses on dynamics in membrane proteins, particularly photosynthetic light-harvesting systems that are of interest for sustainable energy applications. Following a postdoc at Stanford University, Schlau-Cohen joined the Department of Chemistry faculty in 2015. She earned a bachelor’s degree in chemical physics from Brown University in 2003 followed by a PhD in chemistry at the University of California at Berkeley.

Phiala Shanahan’s research interests are focused around theoretical nuclear and particle physics. In particular, she works to understand the structure and interactions of hadrons and nuclei from the fundamental degrees of freedom encoded in the Standard Model of particle physics. After a postdoc at MIT and a joint position as an assistant professor at the College of William and Mary and senior staff scientist at the Thomas Jefferson National Accelerator Facility, Shanahan returned to the Department of Physics as faculty in 2018. She obtained her BS from the University of Adelaide in 2012 and her PhD, also from the University of Adelaide, in 2015.

Omer Yilmaz explores the impact of dietary interventions on stem cells, the immune system, and cancer within the intestine. By better understanding how intestinal stem cells adapt to diverse diets, his group hopes to identify and develop new strategies that prevent and reduce the growth of cancers involving the intestinal tract. Yilmaz joined the Department of Biology in 2014 and is now also a member of Koch Institute for Integrative Cancer Research. After receiving his BS from the University of Michigan in 1999 and his PhD and MD from University of Michigan Medical School in 2008, he was a resident in anatomic pathology at Massachusetts General Hospital and Harvard Medical School until 2013.

In 2023, five MIT faculty were granted tenure in the School of Science:

Physicist Riccardo Comin explores the novel phases of matter that can be found in electronic solids with strong interactions, also known as quantum materials. His group employs a combination of synthesis, scattering, and spectroscopy to obtain a comprehensive picture of these emergent phenomena, including superconductivity, (anti)ferromagnetism, spin-density-waves, charge order, ferroelectricity, and orbital order. Comin joined the Department of Physics in 2016 after postdoctoral work at the University of Toronto. He completed his undergraduate studies at the Universita’ degli Studi di Trieste in Italy, where he also obtained a MS in physics in 2009. Later, he pursued doctoral studies at the University of British Columbia, Canada, earning a PhD in 2013.

Netta Engelhardt researches the dynamics of black holes in quantum gravity and uses holography to study the interplay between gravity and quantum information. Her primary focus is on the black hole information paradox, that black holes seem to be destroying information that, according to quantum physics, cannot be destroyed. Engelhardt was a postdoc at Princeton University and a member of the Princeton Gravity Initiative prior to joining the Department of Physics in 2019. She received her BS in physics and mathematics from Brandeis University and her PhD in physics from the University of California at Santa Barbara. Engelhardt is a researcher in the Laboratory for Nuclear Science’s Center for Theoretical Physics and the Black Hole Initiative at Harvard University.

Mark Harnett studies how the biophysical features of individual neurons endow neural circuits with the ability to process information and perform the complex computations that underlie behavior. As part of this work, his lab was the first to describe the physiological properties of human dendrites. He joined the Department of Brain and Cognitive Sciences and the McGovern Institute for Brain Research in 2015. Prior, he was a postdoc at the Howard Hughes Medical Institute’s Janelia Research Campus. He received his BA in biology from Reed College in Portland, Oregon and his PhD in neuroscience from the University of Texas at Austin.

Or Hen investigates quantum chromodynamic effects in the nuclear medium and the interplay between partonic and nucleonic degrees of freedom in nuclei. Specifically, Hen utilizes high-energy scattering of electron, neutrino, photon, proton and ion off atomic nuclei to study short-range correlations: temporal fluctuations of high-density, high-momentum, nucleon clusters in nuclei with important implications for nuclear, particle, atomic, and astrophysics. Hen was an MIT Pappalardo Fellow in the Department of Physics from 2015 to 2017 before joining the faculty in 2017. He received his undergraduate degree in physics and computer engineering from the Hebrew University and earned his PhD in experimental physics at Tel Aviv University.

Sebastian Lourido is interested in learning about the vulnerabilities of parasites in order to develop treatments for infectious diseases and expand our understanding of eukaryotic diversity. His lab studies many important human pathogens, including Toxoplasma gondii, to model features conserved throughout the phylum. Lourido was a Whitehead Fellow at the Whitehead Institute for Biomedical Research until 2017, when he joined the Department of Biology and became a Whitehead Member. He earned his BS from Tulane University in 2004 and his PhD from Washington University in St. Louis in 2012.



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