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A peculiar state of matter in layers of semiconductors

Scientists around the world are developing new hardware for quantum computers, a new type of device that could accelerate drug design, financial modeling, and weather prediction. These computers rely on qubits, bits of matter that can represent some combination of 1 and 0 simultaneously. The problem is that qubits are fickle, degrading into regular bits when interactions with surrounding matter interfere. But new research at MIT suggests a way to protect their states, using a phenomenon called many-body localization (MBL).

MBL is a peculiar phase of matter, proposed decades ago, that is unlike solid or liquid. Typically, matter comes to thermal equilibrium with its environment. That’s why soup cools and ice cubes melt. But in MBL, an object consisting of many strongly interacting bodies, such as atoms, never reaches such equilibrium. Heat, like sound, consists of collective atomic vibrations and can travel in waves; an object always has such heat waves internally. But when there’s enough disorder and enough interaction in the way its atoms are arranged, the waves can become trapped, thus preventing the object from reaching equilibrium.

MBL had been demonstrated in “optical lattices,” arrangements of atoms at very cold temperatures held in place using lasers. But such setups are impractical. MBL had also arguably been shown in solid systems, but only with very slow temporal dynamics, in which the phase’s existence is hard to prove because equilibrium might be reached if researchers could wait long enough. The MIT research found a signatures of MBL in a “solid-state” system — one made of semiconductors — that would otherwise have reached equilibrium in the time it was watched.

“It could open a new chapter in the study of quantum dynamics,” says Rahul Nandkishore, a physicist at the University of Colorado at Boulder, who was not involved in the work.

Mingda Li, the Norman C Rasmussen Assistant Professor Nuclear Science and Engineering at MIT, led the new study, published in a recent issue of Nano Letters. The researchers built a system containing alternating semiconductor layers, creating a microscopic lasagna — aluminum arsenide, followed by gallium arsenide, and so on, for 600 layers, each 3 nanometers (millionths of a millimeter) thick. Between the layers they dispersed “nanodots,” 2-nanometer particles of erbium arsenide, to create disorder. The lasagna, or “superlattice,” came in three recipes: one with no nanodots, one in which nanodots covered 8 percent of each layer’s area, and one in which they covered 25 percent.

According to Li, the team used layers of material, instead of a bulk material, to simplify the system so dissipation of heat across the planes was essentially one-dimensional. And they used nanodots, instead of mere chemical impurities, to crank up the disorder.

To measure whether these disordered systems are still staying in equilibrium, the researchers measured them with X-rays. Using the Advanced Photon Source at Argonne National Lab, they shot beams of radiation at an energy of more than 20,000 electron volts, and to resolve the energy difference between the incoming X-ray and after its reflection off the sample’s surface, with an energy resolution less than one one-thousandth of an electron volt. To avoid penetrating the superlattice and hitting the underlying substrate, they shot it at an angle of just half a degree from parallel.

Just as light can be measured as waves or particles, so too can heat. The collective atomic vibration for heat in the form of a heat-carrying unit is called a phonon. X-rays interact with these phonons, and by measuring how X-rays reflect off the sample, the experimenters can determine if it is in equilibrium.

The researchers found that when the superlattice was cold — 30 kelvin, about -400 degrees Fahrenheit — and it contained nanodots, its phonons at certain frequencies remained were not in equilibrium.

More work remains to prove conclusively that MBL has been achieved, but “this new quantum phase can open up a whole new platform to explore quantum phenomena,” Li says, “with many potential applications, from thermal storage to quantum computing.”

To create qubits, some quantum computers employ specks of matter called quantum dots. Li says quantum dots similar to Li’s nanodots could act as qubits. Magnets could read or write their quantum states, while the many-body localization would keep them insulated from heat and other environmental factors.

In terms of thermal storage, such a superlattice might switch in and out of an MBL phase by magnetically controlling the nanodots. It could insulate computer parts from heat at one moment, then allow parts to disperse heat when it won’t cause damage. Or it could allow heat to build up and be harnessed later for generating electricity.

Conveniently, superlattices with nanodots can be constructed using traditional techniques for fabricating semiconductors, alongside other elements of computer chips. According to Li, “It’s a much larger design space than with chemical doping, and there are numerous applications.”

“I am excited to see that signatures of MBL can now also be found in real material systems," says Immanuel Bloch, scientific director at the Max-Planck-Institute of Quantum Optics, of the new work. “I believe this will help us to better understand the conditions under which MBL can be observed in different quantum many-body systems and how possible coupling to the environment affects the stability of the system. These are fundamental and important questions and the MIT experiment is an important step helping us to answer them.”

Funding was provided by the U.S. Department of Energy’s Basic Energy Sciences program’s Neutron Scattering Program.

© Image courtesy of the researchers

The setup for the milli-electronvolt inelastic X-ray scattering that probes the many-body localization in the disordered superlattice system

Aziza Almanakly, Belinda Li receive Clare Boothe Luce Graduate Fellowship for Women

MIT PhD students Aziza Almanakly and Belinda Li have been selected as the Department of Electrical Engineering and Computer Science (EECS) recipients of the multi-year Clare Boothe Luce Graduate Fellowship for Women, an honor designed to encourage and support graduate women in STEM. The rigorous selection process for this prestigious fellowship took into account the two students’ outstanding track record of scientific achievement and inquiry, as well as their contributions to the STEM community.

Importantly, the fellowships represent the culmination of an intensive effort on the part of both the Institute and the EECS department. Upon MIT's selection by the Clare Boothe Luce Program for Women in STEM to submit a full proposal, EECS entered the MIT internal competition and was selected to submit a full application on behalf of the Institute to the national competition held by the Henry Luce Foundation. Funds from the Luce Foundation, combined with cost-sharing funds from EECS, will provide full financial support for a period of two years for Almanakly and Li.

“These fellowships are a powerful assertion of institutional support for women in STEM,” says Professor Asu Ozdaglar, head of EECS. “Our dedication to supporting women in STEM extends far beyond attracting top candidates to our program; we are committed to providing continued, concrete support to their research careers once they arrive at MIT.” Both Almanakly and Li will be deferring the start of their CBL Graduate Fellowships until they complete their current fellowship awards; the two recipients are already capturing attention in the red-hot technical fields of quantum computing and language modeling. 

A rising second-year PhD candidate advised by Professor Will Oliver, Aziza Almanakly conducts research on waveguide quantum electrodynamics and microwave quantum optics with superconducting qubits. Within the first nine months of her time at MIT, Almanakly successfully demonstrated controlled, directional generation of single microwave photons on a new qubit chip of her own design — a novel accomplishment, and an indicator of her exceptional talent. Of Almanakly’s work, Oliver says, “Her success is rooted in a combination of raw talent, strong intuition, perseverance, and a strong desire to improve herself, her research, her workplace, and the lives of those around her. I have absolutely no doubt that Aziza will succeed in her research, and I fully expect she will become a future leader in science and technology.” As part of her personal commitment to passing on the mentorship and encouragement she has received, Almanakly teaches the fundamentals of quantum computing to underrepresented high school students through IBM Quantum and the Coding School. Prior to her arrival at MIT, Almanakly conducted research at New York University, Caltech, the City University of New York, and Princeton University. Among other honors, Almanakly has won the P.D. Soros Fellowship for New Americans.

A rising second-year PhD candidate advised by Professor Jacob Andreas, Belinda Li conducts research on language models and natural language processing. Li’s interest in language models and natural language processing was fueled by a year spent working with the AI Integrity team within the Facebook AI Applied Research group, in which she worked on building automated detectors for hate speech and misinformation. Of her work, Li says, “I am interested in interrogating the relationship between language models (LMs) and the knowledge they encode: what exactly do LMs know about the external world? And how can we expand their ability to learn and utilize such knowledge in a systematic way? More fundamentally, what is the relationship between language/language technologies, and the broader society?” Li’s ambitious research goals have taken her far within her first year at MIT. Her advisor Andreas reports: “Despite starting this year [during the pandemic], Belinda has already made significant discoveries about the organization of information in machine learning models trained for language processing tasks … In the six months she’s been here, Belinda has basically started running a mini-lab of her own.” Additionally, Li has taken on the responsibility of mentoring underrepresented undergrads through MIT EECS’s GAAP program. Among many other awards, Li has been named a recipient of the Ida M. Green Memorial Fellowship, the National Science Foundation Graduate Research Fellowship, and the National Defense Science and Engineering Graduate Fellowship.

Established by the prominent American journalist, playwright, ambassador, and Congresswoman Clare Boothe Luce, the CBL Program for Women in STEM was created “to encourage women to enter, study, graduate, and teach” in areas in which they continue to be underrepresented, including science, mathematics, and engineering. To date, the program has supported more than 2,800 women at the undergraduate, graduate, and beginning tenure-track faculty stages, making the CBL program the single most significant source of private support for women in science, mathematics, and engineering in higher education in the United States.

© Photos courtesy of the subjects.

Aziza Almanakly (left) and Belinda Li

Pablo Jarillo-Herrero receives Max Planck-Humboldt Research Award

Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT, has received the 2021 Max Planck-Humboldt Research Award from the Max Planck Society and the Alexander von Humboldt Foundation for his work on two-dimensional quantum materials.

In 2018, Jarillo-Herrero’s research group discovered that by rotating two layers of graphene by a “magic angle,” the bilayer material can be turned from a metal into an electrical insulator or even a superconductor.

Max Planck Society President Martin Stratmann noted Jarillo-Herrero’s research on two-dimensional quantum materials has “opened up a new field of research in which many fundamental insights for both quantum science and quantum technology can be expected.”  

Hans-Christian Pape, president of the Alexander von Humboldt Foundation, said that this research “has the potential to make electronic components more efficient and computers faster and to increase the superconductivity of materials.”

The Max Planck Humboldt Research Award provides 1.5 million euros (about $1.8 million) to enable a five-year collaboration between scientists from German and international research institutions.  

Jarillo-Herrero says his research project, based at the Max Planck Institute for Solid State Research and the University of Stuttgart, will create and investigate novel moiré layer systems. For example, he will develop tuning knobs that can be used to control their properties and will create a technique that allows live tracking of how the angle between two superimposed layers affects their electronic properties.

Some of the quantum materials that Jarillo-Herrero is researching rely on the moiré effect created by a honeycomb pattern created by atoms within two superimposed layers of graphene or similar substances. Twisting the layers against each other creates new patterns; rotating the layers together changes optical patterns and physical properties. In addition, his discovery of the first two-dimensional magnet is leading to other advancements in magnetic research and superconductivity.

Potential applications include improvements in magnetic resonance tomography in medical applications, logical operations in quantum computers, and energy efficiency in electronics.

“Quantum technologies, in particular, have enormous potential for the economy and our society — and we want to tap into that,” says Federal Research Minister Anja Karliczek. “This is why we are particularly pleased about this cross-border cooperation in cutting-edge research.”

Jarillo-Herrero is a professor in the MIT Department of Physics and a native of Spain. He earned his PhD at the Delft University of Technology and completed a postdoc at Columbia University before joining MIT in 2008. He also spent several summers in Germany while studying theoretical physics as a University of Valencia undergraduate.

“I feel really honored to have received this prestigious award by the Max Planck Society and Humboldt Foundation,” says Jarillo-Herrero, who previously earned the APS Oliver E. Buckley Prize and the Wolf Prize in Physics. “One could say I started my scientific career in Germany. So I have very fond memories of my time there, and I am looking forward to interacting and collaborating closely with my colleagues in Stuttgart and elsewhere in Germany.”

Due to coronavirus precautions, this year’s awards will be presented Nov. 3, 2022, in Berlin.

© Photo: Bryce Vickmark

"I feel really honored to have received this prestigious award by the Max Planck Society and Humboldt Foundation,” says Pablo Jarillo-Herrero. "I am looking forward to interacting and collaborating closely with my colleagues in Stuttgart and elsewhere in Germany."

Refugee learners aim to lift up their communities

The MIT Refugee Action Hub (ReACT) recently celebrated the graduation of its third Certificate in Computer and Data Science cohort in an online ceremony. ReACT is a yearlong online learning program that creates education-to-employment pathways for talented refugees and displaced populations.

The graduating cohort of 50 learners represented 22 countries worldwide — by far the broadest representation the program has had, made possible by the shift to all-online programming due to the pandemic. “We were all isolated, but we found this platform where everybody could come from multicultural backgrounds,” says learner Blein Alem. “It’s been more than a community, it’s been like family.”

ReACT is an MIT-wide effort that started in 2017 in response to MIT Solve’s call for refugee education solutions. A key innovation of the MIT ReACT model is the holistic support it brings to online learning, guided by four core pillars: academics, human skills (known sometimes as “soft skills”), professional internships and experiential learning projects, and networking. The program’s robust list of internal partners — including MIT Bootcamps, MIT Abdul Latif Jameel World Education Lab (J-WEL), MITx, and MIT International Science and Technology Initiatives — and external collaborators including organizations, philanthropic supporters, companies, universities, and alumni provide hands-on learning opportunities so ReACT learners can put MIT’s motto of “mens et manus” (“mind and hand”) into practice.

A new kind of online community 

Participants in ReACT’s Certificate in Computer and Data Science program take online undergraduate-level MITx courses in programming, computational thinking, and data science. The learners also participated in interactive online workshops with J-WEL and collaborator Na’amal, an organization that supports skill development for refugees, where they build and test skills in innovation and entrepreneurship, creativity, leadership, and problem-solving. The program wraps up with opportunities for participants to apply their knowledge and skills in a paid onsite or remote internship or experiential learning project with a member of MIT ReACT’s network of organizations.

Traditionally, ReACT offers a blended learning program with an onsite MIT Bootcamp experience in Amman, Jordan. The pandemic underscored the need to provide accessible learning opportunities to displaced and vulnerable populations wherever they are, so the program shifted entirely online in 2020-21. The 50 learners, selected from a vigorous application process, came from very different circumstances across the globe, but the program’s cohort-based model and digital platforms allowed everyone to stay connected, receive support, and motivate each other.

The cohort completed an intensive, 10-week online MIT Innovation Leadership Bootcamp, integrated within the Bootcamp’s larger class of 300 aspiring global entrepreneurs, to build their leadership capacities and new entrepreneurial ventures. Learner Lubna Qarqaz says, “I worked with four different colleagues with way different nationalities and backgrounds. Even though it was challenging at first regarding culture, language, and time differences, we became friends afterward, and we made it to the final top five teams to present our innovation idea in front of a high-quality committee in academics and entrepreneur fields.”

Rigor, connection, and opportunity

The graduation ceremony celebrated the unique challenges the all-virtual cohort faced during a particularly challenging year. ReACT Faculty Director Admir Masic, a professor of civil and environmental engineering at MIT, kicked off the celebrations by sharing how ReACT transformed from idea to a fully-realized program. Once a refugee himself, Masic imparted to the learners, “Knowledge is something no one can take from you.” In his keynote, Acting Vice President for Open Learning Krishna Rajagopal remarked, “Talent has no borders.” The learners also shared their own experiences and showcased their experiential learning projects.

Several learners shared how ReACT opened up new employment pathways in their personal careers. Gloria Carrascal initially found the program challenging due to her level of proficiency in English, but she says, “I got confident after each step through the program. This was a place to learn and be more optimistic and active in life. I got full of energy to work on generating new opportunities each day.” Some of those opportunities included organizing workshops at University of Atlántico and receiving an offer from a Northeastern University professor to apply for her PhD in quantum computing.

Learner Rund Wadi was an electrical engineer, but after her experiential learning project with FreeCodeCamp — an organization that provides high-quality free interactive online training in software engineering — she was inspired to switch career tracks to that field. Another learner, Lubna Qarqaz, was able to use her qualifications as an MIT ReACT learner to secure the job she has now. She then applied her experiences with Python and the Innovation Bootcamp to her current position, resulting in more profit for the company and positive feedback from her managers.

Other groups were also able to leverage their skills and apply what they learned from ReACT to create positive change in their local contexts. Since starting in the program, Alejandra Garcia Isaza has been able to craft methods for tracking the Covid-19 cases and vaccination progress in her home country of Colombia. Another group, named “Nuru Yetu” (meaning “our light” in Swahili), wanted to empower refugees in northern Uganda to install and maintain sustainable energy sources such as solar, leveraging D-Lab curriculum on MIT OpenCourseWare. Learner Rund Wadi also took initiative to translate the curriculum she learned from FreeCodeCamp into Arabic so she could share it with fellow learners and refugees.

One of the final learner presentations was from Amisi Jospin Hassan, who formed the organization ADAI Circle within the last year so he could share his knowledge about data science and artificial intelligence with other people in the Dzaleka Refugee Camp and surrounding villages in Malawi. Today, ADAI Circle has a building that’s part coworking space, electronic lab, computer lab, gaming space, and more, where they provide mentorship for youth and other consulting.

MIT ReACT holds that education has the power to create new opportunities, livelihoods, and hope for refugees and displaced learners. ReACT is now accepting applications for the fourth offering of its Certificate in Computer and Data Science (CDS) program, which will begin January 2022. With over 100 open seats, supported by Western Union Foundation and individual supporters like John and Maria Pfeffer, the new cohort of the year-long online learning program for talented refugees and underserved learners worldwide will be the largest to date.

As Rajagopal said to this graduating cohort, “My challenge to you is, how will you open your learning to build your communities up? How will you offer your shoulders for others to stand on?”

© Image: Angela Zhang

A cohort of 50 graduating learners at the MIT Refugee Action Hub represented 22 countries worldwide — by far the broadest representation the program has had, made possible by the shift to all-online programming due to the pandemic.

Creating dynamic symmetry in quantum systems

Physicists and engineers have long been interested in creating new forms of matter, those not typically found in nature. Such materials might find use someday in, for example, novel computer chips. Beyond applications, they also reveal elusive insights about the fundamental workings of the universe. Recent work at MIT both created and characterized new quantum systems demonstrating dynamical symmetry — particular kinds of behavior that repeat periodically, like a shape folded and reflected through time.

“There are two problems we needed to solve,” says Changhao Li, a graduate student in the lab of Paola Cappellaro, a professor of nuclear science and engineering. Li published the work recently in Physical Review Letters, together with Cappellaro and fellow graduate student Guoqing Wang. “The first problem was that we needed to engineer such a system. And second, how do we characterize it? How do we observe this symmetry?”

Concretely, the quantum system consisted of a diamond crystal about a millimeter across. The crystal contains many imperfections caused by a nitrogen atom next to a gap in the lattice — a so-called nitrogen-vacancy center. Just like an electron, each center has a quantum property called a spin, with two discrete energy levels. Because the system is a quantum system, the spins can be found not only in one of the levels, but also in a combination of both energy levels, like Schrodinger’s theoretical cat, which can be both alive and dead at the same time.

The energy level of the system is defined by its Hamiltonian, whose periodic time dependence the researchers engineered via microwave control. The system was said to have dynamical symmetry if its Hamiltonian was the same not only after every time period t but also after, for example, every t/2 or t/3, like folding a piece of paper in half or in thirds so that no part sticks out. Georg Engelhardt, a postdoc at the Beijing Computational Science Research, who was not involved in this work but whose own theoretical work served as a foundation, likens the symmetry to guitar harmonics, in which a string might vibrate at both 100 hertz and 50 Hz.

To induce and observe such dynamical symmetry, the MIT team first initialized the system using a laser pulse. Then they directed various selected frequencies of microwave radiation at it and let it evolve, allowing it to absorb and emit the energy. “What’s amazing is that when you add such driving, it can exhibit some very fancy phenomena,” Li says. “It will have some periodic shake.” Finally, they shot another laser pulse at it and measured the visible light that it fluoresced, in order to measure its state. The measurement was only a snapshot, so they repeated the experiment many times to piece together a kind of flip book that characterized its behavior across time.

“What is very impressive is that they can show that they have this incredible control over the quantum system,” Engelhardt says. “It’s quite easy to solve the equation, but realizing this in an experiment is quite difficult.”

Critically, the researchers observed that the dynamically symmetry of the Hamiltonian — the harmonics of the system’s energy level — dictated which transitions could occur between one state and another. “And the novelty of this work,” Wang says, “is also that we introduce a tool that can be used to characterize any quantum information platform, not just nitrogen-vacancy centers in diamonds. It’s broadly applicable.” Li notes that their technique is simpler than previous methods, those that require constant laser pulses to drive and measure the system’s periodic movement.

One engineering application is in quantum computers, systems that manipulate qubits, bits that can be not only 0 or 1, but a combination of 0 and 1. A diamond’s spin can encode one qubit in its two energy levels.

Qubits are delicate: they easily break down into simple bit, a 1 or a 0. Or the qubit might become the wrong combination of 0 and 1. “These tools for measuring dynamical symmetries,” Engelhardt says, “can be used to as a sanity check that your experiment is tuned correctly — and with a very high precision.” He notes the problem of outside perturbations in quantum computers, which he likens to a de-tuned guitar. By tuning the tension of the strings — adjusting the microwave radiation — such that the harmonics match some theoretical symmetry requirements, one can be sure that the experiment is perfectly calibrated. 

The MIT team already has their sights set on extensions to this work. “The next step is to apply our method to more complex systems and study more interesting physics,” Li says. They aim for more than two energy levels — three, or 10, or more. With more energy levels they can represent more qubits. “When you have more qubits, you have more complex symmetries,” Li says. “And you can characterize them using our method here.”

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

© Photo: Guoqing Wang/MIT

Instrumentation setup in the Quantum Engineering Group at MIT to study dynamical symmetries with qubits in diamond crystals

Gene Dresselhaus, influential research scientist in solid-state physics, dies at 91

Gene Dresselhaus, a longtime research physicist at MIT’s Lincoln Laboratory and later the Francis Bitter Magnet Laboratory at MIT (now part of the MIT Plasma Science and Fusion Center), died peacefully at his home in California on Sept. 29. He was 91.

Dresselhaus was a theoretical solid-state physicist whose work focused on the science of materials. He was an early pioneer behind the physics of what is now known as spintronics, a field concerned with a property of electrons called spin. He is the namesake of the Dresselhaus effect, a phenomenon in which spin can affect the energies of electrons within a material.

“Gene Dresselhaus was a brilliant scientist who will be remembered for his pioneering ideas that shaped modern band theory,” says Leonid Levitov, professor of physics at MIT, adding that his work was “central to current efforts to create hardware for quantum computers by exploiting electrical control of spin qubits, and also guided the recent breakthroughs in the emerging areas of quantum spin-Hall effect and topological materials.”

Dresselhaus was also a close research collaborator of his beloved wife, the late MIT Institute Professor Mildred “Millie” Dresselhaus, who died in 2017. His lifelong encouragement and support of Millie was a key contributor to her success at a time when women were often discouraged from pursuing research in science and engineering. And his contributions to the (Mildred) Dresselhaus research group within the departments of Electrical Engineering and Computer Science (EECS) and of Physics influenced a generation of scientists and engineers focused on the inner workings of materials.

Gene Dresselhaus’s death was closely followed by the public announcement that, jointly with Emmanuel Rashba, he had been awarded the 2022 American Physical Society Oliver E Buckley Condensed Matter Physics Prize — considered the most prestigious award granted within the field of condensed-matter physics — for “pioneering research on spin-orbit coupling in crystals, particularly the foundational discovery of chiral spin-orbit interactions, which continue to enable new developments in spin transport and topological materials.” In a coincidence befitting their long and loving partnership, the Buckley award’s past winners include Millie Dresselhaus, who received the prize in 2008.

As Levitov explains, “His early theoretical work showed how the spin-orbit interaction in zinc blende lattice can lead to spin-orbital interaction in the Bloch Hamiltonian. From this work it became evident that the `spin’ degree-of-freedom in a solid is far more than just spin; rather, it describes spin and carrier velocity intertwined in an inseparable manner. Spin is anchored to electron momentum in predictably different ways governed by crystal symmetry, enabling a plethora of schemes to manipulate and control spins. The Dresselhaus effect, derived directly from the group theory and symmetry considerations, resonates strongly with current interests in the Dirac and Weyl points, and their relation to symmetry and topology of bands in solids. These effects underpin dissipationless spin transport and other beautiful spin-electric phenomena. The significance of these effects, discovered long ago, has grown tremendously in recent years.”

Born November 9, 1929, in the Panama Canal Zone, Gene F. Dresselhaus studied physics as both an undergraduate and graduate student at the University of California at Berkeley, under condensed-matter physicist Charles Kittel. While at UC-Berkeley, he was involved in work that has become, according to Levitov, “a cornerstone of semiconductor physics, the first successful measurement of cyclotron resonance of charge carriers in solids. This work, which paved the way to the development of experimental techniques for determination of electron Bloch bands, relied on the expertise gained by the U.S. physicists during World War II in the development of radar.” Dresselhaus recalled his work on cyclotron resonance in detail in a later memoir.

Next, Dresselhaus performed postdoctoral work at the University of Chicago, meeting his eventual life partner Millie Dresselhaus while she was a graduate student there. The two married in 1958 and moved together to Cornell University, where Gene was hired as junior faculty member and Millie pursued postdoctoral work, both in the physics group of Albert Overhauser. Their first child, Marianne Dresselhaus ’81, was born while the two lived at Cornell.

When Overhauser soon left Cornell for another position, Gene and Millie faced a significant dilemma. At the time, academia’s famous two-body problem was even thornier than it is today, and many research institutions would not hire women, especially if they were married to a male affiliate. While Overhauser had been supportive of Millie, Cornell declined to employ her on a permanent basis after the conclusion of her postdoc. So, Gene decided to give up his professorship so that he and Millie could find a place to work together. When the Dresselhauses received offers from both IBM and MIT’s Lincoln Laboratory, the couple selected MIT, joining Lincoln’s Solid State Division in 1960.

The Dresselhauses had three more children after joining Lincoln Laboratory: sons Carl, Paul ’85, and Eliot. Millie would eventually pursue a professorship at MIT in 1967, while Gene stayed on at Lincoln for another decade before moving himself to the MIT campus in the mid 1970s. All four of their children would grow up in and around MIT, and were fixtures in their parents’ laboratory spaces. Their numerous graduate students also formed a large extended family of sorts, enjoying the titles of “aunt” and “uncle” to the Dresselhaus children and building close relationships based on the love of science and experimentation.

Gene and Millie Dresselhaus would prove their commitment to each other many times over during the decades to follow, supporting each other through all the challenges that both science and parenthood could present. “When [Millie] hit hurdles, [Gene] encouraged her. When she faced discrimination, he defended her,” daughter Marianne recalled many years later, in an essay coauthored with her own daughter Shoshi, about Gene and Millie’s remarkable partnership. “When she became president of APS [the American Physical Society], he declared the chair at the head of the table the ‘President’s Chair’… At the office, they used each of their skill sets to complement the other. Gene let Millie lecture, while he did the figures and the computer work. He was a theorist; Millie was an experimentalist. Millie would write, and Gene would edit. To be a student of one was to be a student of both. They were always a team, throughout their lives.”

Gene Dresselhaus’ research home on the MIT campus was the Francis Bitter National Magnet Lab, later the Francis Bitter Magnet Lab after national funding moved to Florida in the 1990s. There, Dresselhaus worked on Raman spectroscopy and other low energy spectroscopy for materials. Eventually, the Magnet Lab joined with the MIT Plasma Science and Fusion Center, which was where Dresselhaus spent the remainder of his scientific career.

Gene Dresselhaus also contributed unofficially — but unequivocally — to the research group of Mildred Dresselhaus, based in MIT Building 13. He produced thoughtful work in many aspects of physics, especially emerging work on carbon-based materials like nanotubes and later graphene. He was a frequent coauthor with Millie on her copious research papers and eight books, including “Solid State Properties: From Bulk to Nano;” “Carbon Nanotubes: Advanced Topics in the Synthesis, Structure, Properties and Applications;” and “Group Theory: Application to the Physics of Condensed Matter.”

Dresselhaus will be fondly remembered not only by the many generations of graduate students whose careers he helped to launch, but by the coworkers who recalled his great gift for joyful collaboration. Pablo Jarillo-Herrero, Cecil and Ida Green Professor of Physics at MIT, says, “I have very fond memories of Gene Dresselhaus. Besides being a great physicist, he had a great sense of humor, and he was always Millie Dresselhaus' biggest fan and supporter. They will be remembered as one of the greatest physics couples in history.”

In a remembrance she shared at Dresselhaus’s memorial service, Jing Kong, MIT professor of EECS, said, “It was my great fortune seeing their life example as I was starting my career. Each day around 5 p.m., Millie and Gene would go home together, walking along the hallway, greeting everyone and saying goodbye. I had also heard that they came in together at 5 a.m. This was how Gene put it: ‘You know, when I was retired, Millie asked me if I wanted to come to her lab and work part-time. I discovered part-time is only 12 hours a day.’” The couple’s dedication to their work was matched only by their dedication to the success of their students, former students, and coworkers. Kong added, “On the board outside my office, there are many photos of Millie and collaborators. Each time when someone sent Millie photos, either a new baby, or a graduation, it used to be Gene who would print them out and hang outside Millie’s office proudly. Now these have become treasures in our memories.”

Gene Dresselhaus is survived by his four children and their families: Marianne Dresselhaus Cooper ’81 and husband Geoffrey ’80, ’83; Carl Dresselhaus; Paul Dresselhaus ’85 and wife Maria; Eliot Dresselhaus and wife Françoise; and five grandchildren — Elizabeth Dresselhaus, Clara Dresselhaus, Shoshi Dresselhaus-Cooper, Leora Dresselhaus-Marais PhD ’18 and husband Stephen Dresselhaus-Marais, and Simon Dresselhaus.

© Photo courtesy of the Dresselhaus family.

Gene Dresselhaus alongside his beloved wife Millie Dresselhaus, with whom he shared a lab at MIT.

New material could be two superconductors in one

MIT physicists and colleagues have demonstrated an exotic form of superconductivity in a new material the team synthesized only about a year ago. Although predicted in the 1960s, until now this type of superconductivity has proven difficult to stabilize. Further, the scientists found that the same material can potentially be manipulated to exhibit yet another, equally exotic form of superconductivity.

The work was reported in the Nov. 3 issue of the journal Nature.

The demonstration of finite momentum superconductivity in a layered crystal known a natural superlattice means that the material can be tweaked to create different patterns of superconductivity within the same sample. And that, in turn, could have implications for quantum computing and more.

The material is also expected to become an important tool for plumbing the secrets of unconventional superconductors. This may be useful for new quantum technologies. Designing such technologies is challenging, partly because the materials they are composed of can be difficult to study. The new material could simplify such research because, among other things, it is relatively easy to make.

“An important theme of our research is that new physics comes from new materials,” says Joseph Checkelsky, lead principal investigator of the work and the Mitsui Career Development Associate Professor of Physics. “Our initial report last year was of this new material. This new work reports the new physics.”

Checkelsky’s co-authors on the current paper include lead author Aravind Devarakonda PhD '21, who is now at Columbia University. The work was a central part of Devarakonda’s thesis. Co-authors are Takehito Suzuki, a former research scientist at MIT now at Toho University in Japan; Shiang Fang, a postdoc in the MIT Department of Physics; Junbo Zhu, an MIT graduate student in physics; David Graf of the National High Magnetic Field Laboratory; Markus Kriener of the RIKEN Center for Emergent Matter Science in Japan; Liang Fu, an MIT associate professor of physics; and Efthimios Kaxiras of Harvard University.

New quantum material

Classical physics can be used to explain any number of phenomena that underlie our world — until things get exquisitely small. Subatomic particles like electrons and quarks behave differently, in ways that are still not fully understood. Enter quantum mechanics, the field that tries to explain their behavior and resulting effects.

Checkelsky and colleagues discovered a new quantum material, or one that manifests the exotic properties of quantum mechanics at a macroscopic scale. In this case, the material in question is a superconductor.

Checkelsky explains that fairly recently there has been a boom of realizing special superconductors that are two-dimensional, or only a few atomic layers thick. These new ultrathin superconductors are of interest in part because they are expected to give insights into superconductivity itself.

But there are challenges. For one, materials only a few atomic layers thick are themselves difficult to study because they are so delicate. Could there be another approach to plumbing their secrets?

The new material made by Checkelsky and colleagues can be thought of as the superconducting equivalent of a layer cake, where one layer is an ultrathin film of superconducting material, while the next is an ultrathin spacer layer that protects it. Stacking these layers one atop another results in a large crystal (this happens naturally when the constituent elements of sulfur, niobium, and barium are heated together). “And that macroscopic crystal, which I can hold in my hand, behaves like a 2D superconductor. It was very surprising,” Checkelsky says.

Many of the probes scientists use to study 2D superconductors are challenging to use on atomically thin materials. Because the new material is so large, “we now have many more tools [to characterize it],” Checkelsky says. In fact, for the work reported in the current paper the scientists used a technique that requires massive samples.

Exotic superconductors

A superconductor carries charge in a special way. Instead of via one electron, charge is carried by two electrons bound together in what is known as a Cooper pair. Not all superconductors are the same, however. Some unusual forms of superconductivity can only appear when the Cooper pairs can move unimpeded through the material across relatively long distances. The longer the distance, the “cleaner” the material.

The Checkelsky team’s material is extremely clean. As a result, the physicists were excited to see if it might exhibit an unusual superconducting state, which it does. In the current paper the team shows that their new material is a finite momentum superconductor upon the application of a magnetic field. This particular kind of superconductivity, which was proposed in the 1960s, has remained a fascination to scientists.

While superconductivity is usually destroyed by modest magnetic fields, a finite momentum superconductor can persist further by forming a regular pattern of regions with lots of Cooper pairs and regions that have none. It turns out this kind of superconductor can be manipulated to form a variety of unusual patterns as Cooper pairs move between quantum mechanical orbits known as Landau levels. And that means, Checkelsky says, that scientists should now be able to create different patterns of superconductivity within the same material.

“This is a striking experiment which is able to demonstrate Cooper pairs moving between Landau levels in a superconductor, something that has never been observed before. Frankly, I never anticipated seeing this in a crystal you could hold in your hand, so this is very exciting. To observe this elusive effect, the authors had to perform painstaking, high-precision measurements on a uniquely two-dimensional superconductor that they had previously discovered. It's a remarkable achievement, not only in its technical difficulty, but also in its cleverness,” says Kyle Shen, professor of physics at Cornell University. Shen was not involved in the study.

Further, the physicists realized that their material also has the ingredients for yet another exotic kind of superconductivity. Topological superconductivity involves the movement of charge along edges or boundaries. In this case, that charge could travel along the edges of each internal superconducting pattern.

The Checkelsky team is currently working to see if their material is indeed capable of topological superconductivity. If so, “can we combine both new types of superconductivity? What could that bring?” Checkelsky asks.

“It’s been a lot of fun realizing this new material,” he concludes. “As we’ve dug into understanding what it can do, there have been a number of surprises. It’s really exciting when new things come out that we don’t expect.”

This work was supported by the Gordon and Betty Moore Foundation, the Office of Naval Research, the U.S. Department of Energy (DOE) Office of Science, the National Science Foundation (NSF), and the Rutgers Center for Materials Theory.

Computations were performed at Harvard University. Other parts of the work were performed at the National High Magnetic Field Laboratory, which is supported by the NSF, the State of Florida, and Department of Energy.

© Photo: Denis Paiste

Aravind Devarakonda PhD '21 is lead author of a paper describing an exotic form of superconductivity.

MIT Lincoln Laboratory wins nine R&D 100 Awards for 2021

Nine technologies developed at MIT Lincoln Laboratory have been selected as R&D 100 Award winners for 2021. Since 1963, this awards program has recognized the 100 most significant technologies transitioned to use or introduced into the marketplace over the past year. The winners are selected by an independent panel of expert judges. R&D World, an online publication that serves research scientists and engineers worldwide, announces the awards.

The winning technologies are diverse in their applications. One technology empowers medics to initiate life-saving interventions at the site of an emergency; another could help first responders find survivors buried under rubble. Others present new approaches to building motors at the microscale, combining arrays of optical fibers, and reducing electromagnetic interference in circuit boards. A handful of the awardees leverage machine learning to enable novel capabilities.

Field-programmable imaging array

Advanced imagers, such as lidars and high-resolution wide-field-of-view sensors, need the ability to process huge amounts of data directly in the system, or "on chip." However, developing this capability for novel or niche applications is prohibitively expensive. To help designers overcome this barrier, Lincoln Laboratory developed a field-programmable imaging array to make high-performance on-chip digital processing available to a broad spectrum of new imaging applications.

The technology serves as a universal digital back end, adaptable to any type of optical detector. Once a front end for a specific detector type is integrated, the design cycle for new applications of that detector type can be greatly shortened.

Free-space Quantum Network Link Architecture

The Free-space Quantum Network Link Architecture enables the generation, distribution, and interaction of entangled photons across free-space links. These capabilities are crucial for the development of emerging quantum network applications, such as networked computing and distributed sensing.

Three primary technologies make up this system: a gigahertz clock-rate, three-stage pump laser system; a source of spectrally pure and long-duration entangled photons; and a pump-forwarding architecture that synchronizes quantum systems across free-space links with high precision. This architecture was successfully demonstrated over a 3.2-kilometer free-space atmospheric link between two buildings on Hanscom Air Force Base.

Global Synthetic Weather Radar

The Global Synthetic Weather Radar (GSWR) provides radar-like weather imagery and radar-forward forecasts for regions where actual weather radars are not deployed or are limited in range. The technology generates these synthetic images by using advanced machine learning techniques that combine satellite, lightning, numerical weather model, and radar truth data to produce its predictions.

The laboratory collaborated with the U.S. Air Force on this technology, which will help mission planners schedule operations in remote regions of the world. GSWR’s reliable imagery and forecasts can also provide decision-making guidance for emergency responders and for the transportation, agriculture, and tourism industries.

Guided Ultrasound Intervention Device

The Guided Ultrasound Intervention Device (GUIDE) is the first technology to enable a medic or emergency medical technician to catheterize a major blood vessel in a pre-hospital environment. This procedure can save lives from hemorrhage after traumatic injury.

To use GUIDE, a medic scans a target area of a patient with an ultrasound probe integrated with the device. The device then uses artificial intelligence software to locate a femoral vessel in real time and direct the medic to it via a gamified display. Once in position, the device inserts a needle and guide wire into the vessel, after which the medic can easily complete the process of catheterization. Similar to the impact of automated external defibrillators, GUIDE can empower non-experts to take life-saving measures at the scene of an emergency.

Microhydraulic motors

Microhydraulic motors provide a new way of making things move on a microscale. These tiny actuators are constructed by layering thin, disc-shaped polymer sheets on top of microfabricated electrodes and inserting droplets of water and oil in between the layers. A voltage applied to the electrodes distorts the surface tension of the droplets, causing them to move and rotate the entire disk with them.

These precise, powerful, and efficient motors could enable shape-changing materials, self-folding displays, or microrobots for medical procedures.

Monolithic fiber array launcher

A fiber array launcher is a subsystem that holds an array of optical fibers in place and shapes the laser beams emanating from the fibers. Traditional launchers are composed of many small components, which can become misaligned with vibration and are made of inefficient materials that absorb light. To address these problems, the laboratory developed a monolithic fiber array launcher.

Built out of a single piece of glass, this launcher is one-tenth the volume of traditional arrays and less susceptible to thermo-optic effects to allow for scaling to much higher laser powers and channel counts.

Motion Under Rubble Measured Using Radar

The Motion Under Rubble Measured Using Radar (MURMUR) technology was created to help rescue teams save lives in complex disaster environments. This remote-controlled system is mounted on a robotic ground vehicle for rapid deployment and uses radar to transmit low-frequency signals that penetrate walls, rubble, and debris. 

Signals that reflect back to the radar are digitized and then processed using both classical signal processing techniques and novel machine learning algorithms to determine the range in depth at which there is life-indicating motion, such as breathing, from someone buried under the rubble. Search-and-rescue personnel monitor these detections in real time on a mobile device, reducing time-consuming search efforts and enabling timely recovery of survivors.

Spectrally Efficient Digital Logic

Spectrally Efficient Digital Logic (SEDL) is a set of digital logic building blocks that operate with intrinsically low electromagnetic interference (EMI) emissions.

EMI emissions cause interference between electrical components and present security risks. These emission levels are often discovered late in the electronics development process, once all the pieces are put together, and are thus costly to fix. SEDL is designed to reduce EMI problems while being compatible with traditional logic, giving designers the freedom to construct systems composed of SEDL components entirely or a hybrid of traditional logic and SEDL. It also comes at comparable size, cost, and clock speed with respect to traditional logic.

Traffic Flow Impact Tool

Developed in collaboration with the Federal Aviation Administration, the Traffic Flow Impact Tool helps air traffic control managers handle disruptions to air traffic caused by dangerous weather, such as thunderstorms.

The tool uses a novel machine learning technique to fuse multiple convective weather forecast models and compute a metric called permeability, a measure of the amount of usable airspace in a given area. These permeability predictions are displayed on a user interface and allow managers to plan ahead for weather impacts to air traffic.

Since 2010, Lincoln Laboratory has received 75 R&D 100 Awards. The awards are a recognition of the laboratory's transfer of unclassified technologies to industry and government. Each year, many technology transitions also occur for classified projects. This transfer of technology is central to the laboratory's role as a federally funded research and development center.

"Our R&D 100 Awards recognize the significant, ongoing technology development and transition success at the laboratory. We have had much success with our classified work as well," says Eric Evans, the director of Lincoln Laboratory. "We are very proud of everyone involved in these programs."

Editors of R&D World announced the 2021 R&D 100 Award winners at virtual ceremonies broadcast on October 19, 20, and 21.

© Photo: Glen Cooper

This field-programmable imaging array chip has more 6.6 billion transistors. It was one of nine technologies developed at Lincoln Laboratory to be honored with an R&D 100 award for 2021.

Azure Quantum and Classiq collaborate to offer researchers and educators accelerated quantum algorithm design

8 February 2023 at 17:00

Today, Classiq and Microsoft launched a quantum research and education program that offers educational institutions access to Classiq's state-of-the-art Quantum software platform coupled with Azure Quantum cloud access to diverse quantum hardware.

This educational collaboration is an important building block in Microsoft's strategy to bring quantum at scale to the world. By empowering educators, researchers and students with leading quantum technologies on the Azure Quantum platform, we are helping accelerate the collective innovation needed to ultimately achieve impact with quantum at scale.

Classiq, which provides a leading platform for designing, analyzing, and executing quantum circuits, selected Azure Quantum to be its launch partner for its global academic program. Through integration with Azure Quantum, Classiq enables university professors, students, and researchers to speed up algorithm design on quantum computers, bypassing quantum assembly-level language so that users can focus on designing applications instead of gate-level code.

Two people sitting at computers. The computer screens have Classiq's synthesis engine software on them.

In addition to designing state-of-the-art circuits for near-term quantum devices, Classiq's synthesis engine allows researchers to easily explore large complex quantum circuits. The circuits, generated in QIR code, can then be sent to Azure Quantum's resource estimation service, providing practitioners and classrooms critical insight with respect to designing quantum applications for the fault-tolerant quantum computers of tomorrow.

Azure Quantum and Classiq collaborate to empower educators worldwide

Azure Quantum was the natural choice for Classiq to collaborate with as its academic program launch partner.

"The combined offering seamlessly pairs Classiq's easy-to-use software design platform with Azure Quantum's robust portfolio of NISQ hardware, resource estimator, and hybrid quantum computing features. The pairing enables quantum researchers and educators to focus on application development uninhibited by low-level code. This program reflects Classiq and Azure Quantum's deep and shared commitment to invest in global workforce development."

Nir Minerbi, Co-Founder and CEO of Classiq

The combined offering will empower professors worldwide, including those already in Classiq and Azure Quantum's networks across leading institutions, to teach courses and conduct research in all aspects of quantum computing.

“In order to make quantum computing a success, we need a strong interplay between hardware and software. Designing quantum software at the functional level and executing it on multiple QPUs will advance both quantum research and education. The collaboration between Classiq and Microsoft aims at exactly that and will pave the way towards a quantum computing ecosystem capable of solving some of the future's most important challenges."

Dr. Robert Wille, Technical University of Munich Professor and Chair for Design Automation of the Bavarian State Ministry for Science and Arts

The joint offering accelerates quantum software education by providing an advanced platform for automated quantum software design, with seamless execution on quantum hardware.

"The Classiq platform's ability to simplify complex quantum circuits through visualization and automation, in fact, mirrors Classiq's integration approach with Azure Quantum. Users access the best of Classiq's quantum circuit design software and Azure Quantum's cloud-based endpoints and capabilities through a single, simple-to-use Classiq interface and workspace."

Fabrice Frachon, Azure Quantum Principal Program Manager

Azure Quantum is ready to meet learners and practitioners wherever they are in their quantum journey. This new academic program supports application development-focused teams, with only nominal quantum software programming experience required. Because of its functional descriptive approach, Classiq makes it easy to upskill domain experts with little quantum experience and integrate them into high-performing quantum teams.

This global program expands the research and learning applications of Azure Quantum as well as the Azure Quantum for Educators portfolio of approaches, resources, and tools to facilitate the critical objective of skilling up a quantum-ready workforce.

Explore Azure Quantum and Classiq

Learn more about Classiq Academia.

The post Azure Quantum and Classiq collaborate to offer researchers and educators accelerated quantum algorithm design appeared first on Microsoft Azure Quantum Blog.

How ultracold, superdense atoms become invisible

An atom’s electrons are arranged in energy shells. Like concertgoers in an arena, each electron occupies a single chair and cannot drop to a lower tier if all its chairs are occupied. This fundamental property of atomic physics is known as the Pauli exclusion principle, and it explains the shell structure of atoms, the diversity of the periodic table of elements, and the stability of the material universe.

Now, MIT physicists have observed the Pauli exclusion principle, or Pauli blocking, in a completely new way: They’ve found that the effect can suppress how a cloud of atoms scatters light.

Normally, when photons of light penetrate a cloud of atoms, the photons and atoms can ping off each other like billiard balls, scattering light in every direction to radiate light, and thus make the cloud visible. However, the MIT team observed that when atoms are supercooled and ultrasqueezed, the Pauli effect kicks in and the particles effectively have less room to scatter light. The photons instead stream through, without being scattered.

In their experiments, the physicists observed this effect in a cloud of lithium atoms. As they were made colder and more dense, the atoms scattered less light and became progressively dimmer. The researchers suspect that if they could push the conditions further, to temperatures of absolute zero, the cloud would become entirely invisible.

The team’s results, reported today in Science, represent the first observation of Pauli blocking’s effect on light-scattering by atoms. This effect was predicted 30 years ago but not observed until now.

“Pauli blocking in general has been proven, and is absolutely essential for the stability of the world around us,” says Wolfgang Ketterle, the John D. Arthur Professor of Physics at MIT. “What we’ve observed is one very special and simple form of Pauli blocking, which is that it prevents an atom from what all atoms would naturally do: scatter light. This is the first clear observation that this effect exists, and it shows a new phenomenon in physics.”

Ketterle’s co-authors are lead author and former MIT postdoc Yair Margalit, graduate student Yu-Kun Lu, and Furkan Top PhD ’20. The team is affiliated with the MIT Physics Department, the MIT-Harvard Center for Ultracold Atoms, and MIT’s Research Laboratory of Electronics (RLE).

A light kick

When Ketterle came to MIT as a postdoc 30 years ago, his mentor, David Pritchard, the Cecil and Ida Green Professor of Physics, made a prediction that Pauli blocking would suppress the way certain atoms known as fermions scatter light.

His idea, broadly speaking, was that if atoms were frozen to a near standstill and squeezed into a tight enough space, the atoms would behave like electrons in packed energy shells, with no room to shift their velocity, or position. If photons of light were to stream in, they wouldn’t be able to scatter.

“An atom can only scatter a photon if it can absorb the force of its kick, by moving to another chair,” explains Ketterle, invoking the arena seating analogy. “If all other chairs are occupied, it no longer has the ability to absorb the kick and scatter the photon. So, the atoms become transparent.”

“This phenomenon had never been observed before, because people were not able to generate clouds that were cold and dense enough,” Ketterle adds.

“Controlling the atomic world”

In recent years, physicists including those in Ketterle’s group have developed magnetic and laser-based techniques to bring atoms down to ultracold temperatures. The limiting factor, he says, was density.

“If the density is not high enough, an atom can still scatter light by jumping over a few chairs until it finds some room,” Ketterle says. “That was the bottleneck.”

In their new study, he and his colleagues used techniques they developed previously to first freeze a cloud of fermions — in this case, a special isotope of lithium atom, which has three electrons, three protons, and three neutrons. They froze a cloud of lithium atoms down to 20 microkelvins, which is about 1/100,000 the temperature of interstellar space.  

“We  then used a tightly focused laser to squeeze the ultracold atoms to record densities, which reached about a quadrillion atoms per cubic centimeter,” Lu explains.

The researchers then shone another laser beam into the cloud, which they carefully calibrated so that its photons would not heat up the ultracold atoms or alter their density as the light passed through. Finally, they used a lens and camera to capture and count the photons that managed to scatter away.

“We’re actually counting a few hundred photons, which is really amazing,” Margalit says. “A photon is such a little amount of light, but our equipment is so sensitive that we can see them as a small blob of light on the camera.”

At progressively colder temperatures and higher densities, the atoms scattered less and less light, just as Pritchard’s theory predicted. At their coldest, at around 20 microkelvin, the atoms were 38 percent dimmer, meaning they scattered 38 percent less light than less cold, less dense atoms.

“This regime of ultracold and very dense clouds has other effects that could possibly deceive us,” Margalit says. “So, we spent a few good months sifting through and putting aside these effects, to get the clearest measurement.”

Now that the team has observed Pauli blocking can indeed affect an atom’s ability to scatter light, Ketterle says this fundamental knowledge may be used to develop materials with suppressed light scattering, for instance to preserve data in quantum computers.

“Whenever we control the quantum world, like in quantum computers, light scattering is a problem, and means that information is leaking out of your quantum computer,” he muses. “This is one way to suppress light scattering, and we are contributing to the general theme of controlling the atomic world.”

This research was funded, in part, by the National Science Foundation and the Department of Defense. Related work by teams from the University of Colorado and the University of Otago appears in the same issue of Science.

© Image: Christine Daniloff, MIT

A new study confirms that as atoms are chilled and squeezed to extremes, their ability to scatter light is suppressed.

Sensor based on quantum physics could detect SARS-CoV-2 virus

A novel approach to testing for the presence of the virus that causes Covid-19 may lead to tests that are faster, less expensive, and potentially less prone to erroneous results than existing detection methods. Though the work, based on quantum effects, is still theoretical, these detectors could potentially be adapted to detect virtually any virus, the researchers say.

The new approach is described in a paper published Thursday in the journal Nano Letters, by Changhao Li, an MIT doctoral student; Paola Cappellaro, a professor of nuclear science and engineering and of physics; and Rouholla Soleyman and Mohammad Kohandel of the University of Waterloo.

Existing tests for the SARS-CoV-2 virus include rapid tests that detect specific viral proteins, and polymerase chain reaction (PCR) tests that take several hours to process. Neither of these tests can quantify the amount of virus present with high accuracy. Even the gold-standard PCR tests might have false-negative rates of more than 25 percent. In contrast, the team’s analysis shows the new test could have false negative rates below 1 percent. The test could also be sensitive enough to detect just a few hundred strands of the viral RNA, within just a second.

The new approach makes use of atomic-scale defects in tiny bits of diamond, known as nitrogen vacancy (NV) centers. These tiny defects are extremely sensitive to minute perturbations, thanks to quantum effects taking place in the diamond’s crystal lattice, and are being explored for a wide variety of sensing devices that require high sensitivity.

The new method would involve coating the nanodiamonds containing these NV centers with a material that is magnetically coupled to them and has been treated to bond only with the specific RNA sequence of the virus. When the virus RNA is present and bonds to this material, it disrupts the magnetic connection and causes changes in the diamond’s fluorescence that are easily detected with a laser-based optical sensor.

The sensor uses only low-cost materials (the diamonds involved are smaller than specks of dust), and the devices could be scaled up to analyze a whole batch of samples at once, the researchers say. The gadolinium-based coating with its RNA-tuned organic molecules can be produced using common chemical processes and materials, and the lasers used to read out the results are comparable to cheap, widely available commercial green laser pointers.

While this initial work was based on detailed mathematical simulations that proved the system can work in principle, the team is continuing to work on translating that into a working lab-scale device to confirm the predictions. “We don’t know how long it will take to do the final demonstration,” Li says. Their plan is first to do a basic proof-of-principle lab test, and then to work on ways to optimize the system to make it work on real virus diagnosis applications.

The multidisciplinary process requires a combination of expertise in quantum physics and engineering, for producing the detectors themselves, and in chemistry and biology, for developing the molecules that bind with the viral RNA and for finding ways to bond these to the diamond surfaces.

Even if complications arise in translating the theoretical analysis into a working device,  Cappellaro says, there is such a large margin of lower false negatives predicted from this work that it will likely still have a strong advantage over standard PCR tests in that regard. And even if the accuracy were the same, this method would still have a major advantage in producing its results with a matter of minutes, rather than requiring several hours, she says.

The basic method can be adapted to any virus, she says, including any new ones that may arise, simply by adapting the compounds that are attached to the nanodiamond sensors to match the generic material of the specific target virus.

“The proposed approach is appealing both for its generality and its technological simplicity,” says David Glenn, senior research scientist at Quantum Diamond Technologies Inc., who was not associated with this work. “In particular, the sensitive, all-optical detection technique described here requires minimal instrumentation compared to other methods that employ nitrogen vacancy centers,” he says.

He adds that for his company, “we're very excited about using diamond-based quantum sensors to build powerful tools for biomedical diagnostics. Needless to say, we will be following along with great interest as the ideas presented in this work are translated to the lab.”

The work was supported by the U.S. Army Research Office and the Canada First Research Excellence Fund.

© Courtesy of the researchers, edited by MIT News

Using mathematical simulations, MIT researchers have shown that it would be possible to design a sensor, based on quantum physics, that could detect the SARS-CoV-2 virus.

Quantum information science momentum accelerates in the Pacific Northwest

14 February 2023 at 18:00

Nearly 275 quantum computing enthusiasts convened in January for the Northwest Quantum Nexus Summit around a shared mission to accelerate quantum information science (QIS) research, co-innovation, and workforce development in the Pacific Northwest. The Northwest Quantum Nexus (NQN) coalition brought together 50 speakers and panelists from over 20 organizations for the two-day summit at the University of Washington (UW).

Collage of 4 photos- upper lefthand corner is Dr.Troyer and Student seated while in a discussion, upper righthand corner is 3 speakers seated while one holds a microphone, lower lefthand corner is the Northwest Quantum Nexus logo, and the lower right hand corner is an image of Dr. Krysta Svore speaking at a podium.

“The time is right for regions across the U.S. to ignite around quantum innovation. In the past year alone, the number of U.S. quantum professionals on LinkedIn grew 36% with 3 of the top 5 employers of quantum professionals in the U.S. posting double-digit growth of their talent pools*. The Pacific Northwest is ripe with candidates from the fields of study that most quantum professionals on LinkedIn have in their backgrounds: physics, computer science, computational science, math, and electrical and electronics engineering.”*

Nick DePorter, Senior Lead Manager, U.S. Public Policy and Economic Graph at LinkedIn.
*Source: LinkedIn Talent Insights

Microsoft and fellow NQN founding members Pacific Northwest National Laboratory and the University of Washington are committed to building connections and synergy across the Pacific Northwest to help the quantum community accelerate technical innovation, application development, and a quantum-ready workforce. The end game is to nurture a vibrant, regional quantum economy with national and global impact, and advance QIS technologies to their full potential toward solving some of society's most pressing issues. The summit was kicked off by UW Provost Mark Richards and Charles Tahan, Executive Office of the President, Office of Science and Technology Policy Assistant Director for QIS and Quantum Coordination Office Director.

New members across industry and academia

NQN welcomed five new members from industry and academia to take the stage at the summit: AWS, Boeing, IonQ, the University of Oregon, and Washington State University. The addition of AWS and Boeing brings two of the Pacific Northwest's largest tech leaders into the coalition. AWS discussed the customer verticals interested in quantum computing technologieslogistics, agriculture, machine learning, finance, energy, and pharma. Boeing shared their Disruptive Computing and Networks team's investments in quantum sensing, computing, and networks. IonQ generated excitement around their plans and vision for a 65,000-square-foot Seattle-area campus.

The University of Oregon described scientific programs in the over 50 members of the Oregon Center for Optical Molecular & Quantum Science, including the Oregon Ions program led by Assistant Professor David Allcock and Nobel Prize-winner Professor David Wineland. Washington State University Associate Professor Michael Forbes provided insight into key research areas such as NMR and imaging, analog quantum computing, quantum chaos, atom interferometry, and cryoelectronics.

Driving QIS accessibility and impact

The summit featured a Workforce Development session that brought together Scientific and Business audience tracks in showcases and discussions around workforce development, upskilling, and curriculum collaborations. Dr. Matthias Troyer, Technical Fellow and CVP at Azure Quantum, participated in an onstage conversation with Ewin Tang, a Ph.D. student in the UW theoretical computer science group. They discussed the most promising applications for scaled quantum computing, the hardware resources required to achieve practical quantum advantage, and what can be done by the market and policymakers to drive quantum impact and equity.

The post-event survey results underscored these themes, with attendees wanting more local and state government participation; more frequent summits, scientific forums, and facilitated networking opportunities; member expansion to cover additional organizations and adjacent geographies; and programs to attract entrepreneurs and investors.

In the intervening years since the first Summit, the NQN founding members highlighted progress and impact including Azure Quantum's demonstration of the formerly elusive physics needed to build scalable topological qubits; UW's attraction of $45 million USD in QISE funding to its ECE, Chemistry and Physics departments; and PNNL's new superconducting qubit testbed and HiSVSIM and Ensembled Quantum Computing (EQC) advancements.

A successful first NQN Hackathon 

This year's summit also featured a new NQN Hackathon hosted by Azure Quantum and IonQ where 75 students rolled up their sleeves to tackle hands-on problems. During the hackathon, teams self-organized to build solutions in response to challenges on IonQ's premium 23 algorithmic qubit (#AQ) trapped ion system, Aria. The hybrid event included virtual workshops before the in-person hackathon staffed by Azure Quantum and IonQ teams at the UW campus. Three winning teams were selected by an NQN Member judging panel and celebrated at the summit's close. Read what EyeQ had to say about their experience and check out Team I-Tummy's project.

Five college age students sit at a table with their laptops, smiling at the camera as they participate in the NQN Hackathon.

Unlocking the collective genius of the Pacific Northwest

The summit reinforced the message from keynote speaker, Krysta Svore, Vice President for Advanced Quantum Development at Microsoft: "The promise of quantum will only be realized by unlocking the collective genius, not by one company or institution alone." To connect with the Azure Quantum team, we invite you to join the conversation by registering for the Microsoft Quantum Innovator Seriesthe next webinar is on February 28, 2023 at 9:00 AM PT.

Last but not least, the summit's organizing committee extends its sincere and heartfelt thanks to all NQN session chairs, speakers, panelists, attendees, administrative and operational contributors, and the UW HUB venue. With 94 percent of post-event survey respondents indicating their intent to attend the next summit, we look forward to the momentum continuing.

*LinkedIn Talent Insights data is derived by aggregating profile data voluntarily submitted by LinkedIn members. As such, LinkedIn cannot guarantee the accuracy of LinkedIn Talent Insights data.

The post Quantum information science momentum accelerates in the Pacific Northwest appeared first on Microsoft Azure Quantum Blog.

Physicists discover “secret sauce” behind exotic properties of a new quantum material

MIT physicists and colleagues have discovered the “secret sauce” behind some of the exotic properties of a new quantum material that has transfixed physicists due to those properties, which include superconductivity. Although theorists had predicted the reason for the unusual properties of the material, known as a kagome metal, this is the first time that the phenomenon behind those properties has been observed in the laboratory.

“The hope is that our new understanding of the electronic structure of a kagome metal will help us build a rich platform for discovering other quantum materials,” says Riccardo Comin, the Class of 1947 Career Development Associate Professor of Physics at MIT, whose group led the study. That, in turn, could lead to a new class of superconductors, new approaches to quantum computing, and other quantum technologies.

The work is reported in the Jan. 13 online issue of the journal Nature Physics.

Classical physics can be used to explain any number of phenomena that underlie our world — until things get exquisitely small. Subatomic particles like electrons and quarks behave differently, in ways that are still not fully understood. Enter quantum mechanics, the field that tries to explain their behavior and resulting effects.

The kagome metal at the heart of the current work is a new quantum material, or one that manifests the exotic properties of quantum mechanics at a macroscopic scale. In 2018 Comin and Joseph Checkelsky, MIT’s Mitsui Career Development Associate Professor of Physics, led the first study on the electronic structure of kagome metals, spurring interest into this family of materials. Members of the kagome metal family are composed of layers of atoms arranged in repeating units similar to a Star of David or sheriff’s badge. The pattern is also common in Japanese culture, particularly as a basket-weaving motif.

“This new family of materials has attracted a lot of attention as a rich new playground for quantum matter that can exhibit exotic properties such as unconventional superconductivity, nematicity, and charge-density waves,” says Comin.

Unusual properties

Superconductivity and hints of charge density wave order in the new family of kagome metals studied by Comin and colleagues were discovered in the laboratory of Professor Stephen Wilson at the University of California at Santa Barbara, where single crystals were also synthesized (Wilson is a coauthor of the Nature Physics paper). The specific kagome material explored in the current work is made of only three elements (cesium, vanadium, and antimony) and has the chemical formula CsV3Sb5.

The researchers focused on two of the exotic properties that a kagome metal shows when cooled below room temperatures. At those temperatures, electrons in the material begin to exhibit collective behavior. “They talk to each other, as opposed to moving independently,” says Comin.

One of the resulting properties is superconductivity, which allows a material to conduct electricity extremely efficiently. In a regular metal, electrons behave much like people dancing individually in a room. In a kagome superconductor, when the material is cooled to 3 kelvins (about -454 degrees Fahrenheit) the electrons begin to move in pairs, like couples at a dance. “And all these pairs are moving in unison, as if they were part of a quantum choreography,” says Comin.

At 100 K, the kagome material studied by Comin and collaborators exhibits yet another strange kind of behavior known as charge density waves. In this case, the electrons arrange themselves in the shape of ripples, much like those in a sand dune. “They’re not going anywhere; they’re stuck in place,” Comin says. A peak in the ripple represents a region that is rich in electrons. A valley is electron-poor. “Charge density waves are very different from a superconductor, but they’re still a state of matter where the electrons have to arrange in a collective, highly organized fashion. They form, again, a choreography, but they’re not dancing anymore. Now they form a static pattern.”

Comin notes that kagome metals are of great interest to physicists in part because they can exhibit both superconductivity and charge density waves. “These two exotic phenomena are often in competition with one another, therefore it is unusual for a material to host both of them.”

The secret sauce?

But what is behind the emergence of these two properties? “What causes the electrons to start talking to each other, to start influencing each other? That is the key question,” says first author Mingu Kang, a graduate student in the MIT Department of Physics also affiliated with the Max Planck POSTECH Korea Research Initiative. That’s what the physicists report in Nature Physics. “By exploring the electronic structure of this new material, we discovered that the electrons exhibit an intriguing behavior known as an electronic singularity,” Kang says. This particular singularity is named for Léon van Hove, the Belgian physicist who first discovered it.

The van Hove singularity involves the relationship between the electrons’ energy and velocity. Normally, the energy of a particle in motion is proportional to its velocity squared. “It’s a fundamental pillar of classical physics that [essentially] means the greater the velocity, the greater the energy,” says Comin. Imagine a Red Sox pitcher hitting you with a fast ball. Then imagine a kid trying to do the same. The pitcher’s ball would hurt a lot more than the kid’s, which has less energy.

What the Comin team found is that in a kagome metal, this rule doesn’t hold anymore. Instead, electrons traveling with different velocities happen to all have the same energy. The result is that the pitcher’s fast ball would have the same physical effect as the kid’s. “It’s very counterintuitive,” Comin says. He noted that relating the energy to the velocity of electrons in a solid is challenging and requires special instruments at two international synchrotron research facilities: Beamline 4A1 of the Pohang Light Source and Beamline 7.0.2 (MAESTRO) of the Advanced Light Source at Lawrence Berkeley National Lab.

Comments Professor Ronny Thomale of the Universität Würzburg (Germany): "Theoretical physicists (including my group) have predicted the peculiar nature of van Hove singularities on the kagome lattice, a crystal structure made of corner-sharing triangles. Riccardo Comin has now provided the first experimental verification of these theoretical suggestions." Thomale was not involved in the work.

When many electrons exist at once with the same energy in a material, they are known to interact much more strongly. As a result of these interactions, the electrons can pair up and become superconducting, or otherwise form charge density waves. “The presence of a van Hove singularity in a material that has both makes perfect sense as the common source for these exotic phenomena” adds Kang. “Therefore, the presence of this singularity is the ‘secret sauce’ that enables the quantum behavior of kagome metals.”

The team’s new understanding of the relationship between energy and velocities in the kagome material “is also important because it will enable us to establish new design principles for the development of new quantum materials,” Comin says. Further, “we now know how to find this singularity in other systems.”

Direct feedback

When physicists are analyzing data, most of the time that data must be processed before a clear trend is seen. The kagome system, however, “gave us direct feedback on what’s happening,” says Comin. “The best part of this study was being able to see the singularity right there in the raw data.”

Additional authors of the Nature Physics paper are Shiang Fang of Rutgers University; Jeung-Kyu Kim, Jonggyu Yoo, and Jae-Hoon Park of Max Planck POSTECH/Korea Research Initiative and Pohang University of Science and Technology (Korea); Brenden Ortiz of the University of California, Santa Barbara; Jimin Kim of the Institute for Basic Science (Korea); Giorgio Sangiovanni of the Universität Würzburg (Germany); Domenico Di Sante of the University of Bologna (Italy) and the Flatiron Institute; Byeong-Gyu Park of Pohang Light Source (Korea); Sae Hee Ryu, Chris Jozwiak, Aaron Bostwick and Eli Rotenberg of Lawrence Berkeley National Laboratory; and Efthimios Kaxiras of Harvard University.

This work was funded by the Air Force Office of Scientific Research, the National Science Foundation, the National Research Foundation of Korea, a Samsung Scholarship, a Rutgers Center for Material Theory Distinguished Postdoctoral Fellowship, the California NanoSystems Institute, the European Union Horizon 2020 program, the German Research Foundation, and it used the resources of the Advanced Light Source, a Department of Energy Office of Science user facility.

© Image courtesy of the Comin Laboratory.

A visualization of the zero-energy electronic states — also known as a "Fermi surface" — from the kagome material studied by MIT’s Riccardo Comin and colleagues

Quantum Computing Innovation Panel

There was a Quantum Computing Innovation Panel at the Q2B conference a couple of weeks ago. The Q2B conference had over 800 attendees and 140+ speakers. The Panelists were: Celia Mertzbacker – Quantum economic development consortium (setup by NIST) QEDC Jake Taylor – Chief science officer – Riverlane. Error correction quantum computing, Cambridge UK High ...

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A new language for quantum computing

Time crystals. Microwaves. Diamonds. What do these three disparate things have in common? 

Quantum computing. Unlike traditional computers that use bits, quantum computers use qubits to encode information as zeros or ones, or both at the same time. Coupled with a cocktail of forces from quantum physics, these refrigerator-sized machines can process a whole lot of information — but they’re far from flawless. Just like our regular computers, we need to have the right programming languages to properly compute on quantum computers. 

Programming quantum computers requires awareness of something called “entanglement,” a computational multiplier for qubits of sorts, which translates to a lot of power. When two qubits are entangled, actions on one qubit can change the value of the other, even when they are physically separated, giving rise to Einstein’s characterization of “spooky action at a distance.” But that potency is equal parts a source of weakness. When programming, discarding one qubit without being mindful of its entanglement with another qubit can destroy the data stored in the other, jeopardizing the correctness of the program. 

Scientists from MIT’s Computer Science and Artificial Intelligence (CSAIL) aimed to do some unraveling by creating their own programming language for quantum computing called Twist. Twist can describe and verify which pieces of data are entangled in a quantum program, through a language a classical programmer can understand. The language uses a concept called purity, which enforces the absence of entanglement and results in more intuitive programs, with ideally fewer bugs. For example, a programmer can use Twist to say that the temporary data generated as garbage by a program is not entangled with the program’s answer, making it safe to throw away.

While the nascent field can feel a little flashy and futuristic, with images of mammoth wiry gold machines coming to mind, quantum computers have potential for computational breakthroughs in classically unsolvable tasks, like cryptographic and communication protocols, search, and computational physics and chemistry. One of the key challenges in computational sciences is dealing with the complexity of the problem and the amount of computation needed. Whereas a classical digital computer would need a very large exponential number of bits to be able to process such a simulation, a quantum computer could do it, potentially, using a very small number of qubits — if the right programs are there. 

“Our language Twist allows a developer to write safer quantum programs by explicitly stating when a qubit must not be entangled with another,” says Charles Yuan, an MIT PhD student in electrical engineering and computer science and the lead author on a new paper about Twist. “Because understanding quantum programs requires understanding entanglement, we hope that Twist paves the way to languages that make the unique challenges of quantum computing more accessible to programmers.” 

Yuan wrote the paper alongside Chris McNally, a PhD student in electrical engineering and computer science who is affiliated with the MIT Research Laboratory of Electronics, as well as MIT Assistant Professor Michael Carbin. They presented the research at last week's 2022 Symposium on Principles of Programming conference in Philadelphia.

Untangling quantum entanglement 

Imagine a wooden box that has a thousand cables protruding out from one side. You can pull any cable all the way out of the box, or push it all the way in.

After you do this for a while, the cables form a pattern of bits — zeros and ones — depending on whether they’re in or out. This box represents the memory of a classical computer. A program for this computer is a sequence of instructions for when and how to pull on the cables.

Now imagine a second, identical-looking box. This time, you tug on a cable, and see that as it emerges, a couple of other cables are pulled back inside. Clearly, inside the box, these cables are somehow entangled with each other. 

The second box is an analogy for a quantum computer, and understanding the meaning of a quantum program requires understanding the entanglement present in its data. But detecting entanglement is not straightforward. You can’t see into the wooden box, so the best you can do is try pulling on cables and carefully reason about which are entangled. In the same way, quantum programmers today have to reason about entanglement by hand. This is where the design of Twist helps massage some of those interlaced pieces. 

The scientists designed Twist to be expressive enough to write out programs for well-known quantum algorithms and identify bugs in their implementations. To evaluate Twist's design, they modified the programs to introduce some kind of bug that would be relatively subtle for a human programmer to detect, and showed that Twist could automatically identify the bugs and reject the programs.

They also measured how well the programs performed in practice in terms of runtime, which had less than 4 percent overhead over existing quantum programming techniques.

For those wary of quantum’s “seedy” reputation in its potential to break encryption systems, Yuan says it’s still not very well known to what extent quantum computers will actually be able to reach their performance promises in practice. “There's a lot of research that's going on in post-quantum cryptography, which exists because even quantum computing is not all-powerful. So far, there's a very specific set of applications in which people have developed algorithms and techniques where a quantum computer can outperform classical computers.” 

An important next step is using Twist to create higher-level quantum programming languages. Most quantum programming languages today still resemble assembly language, stringing together low-level operations, without mindfulness towards things like data types and functions, and what’s typical in classical software engineering.

“Quantum computers are error-prone and difficult to program. By introducing and reasoning about the ‘purity’ of program code, Twist takes a big step towards making quantum programming easier by guaranteeing that the quantum bits in a pure piece of code cannot be altered by bits not in that code,” says Fred Chong, the Seymour Goodman Professor of Computer Science at the University of Chicago and chief scientist at

The work was supported, in part, by the MIT-IBM Watson AI Lab, the National Science Foundation, and the Office of Naval Research.

© Photo: Graham Carlow/IBM

While the nascent field of quantum computing can feel flashy and futuristic, quantum computers have the potential for computational breakthroughs in classically unsolvable tasks, like cryptographic and communication protocols, search, and computational physics and chemistry.

Vibrating atoms make robust qubits, physicists find

MIT physicists have discovered a new quantum bit, or “qubit,” in the form of vibrating pairs of atoms known as fermions. They found that when pairs of fermions are chilled and trapped in an optical lattice, the particles can exist simultaneously in two states — a weird quantum phenomenon known as superposition. In this case, the atoms held a superposition of two vibrational states, in which the pair wobbled against each other while also swinging in sync, at the same time.

The team was able to maintain this state of superposition among hundreds of vibrating pairs of fermions. In so doing, they achieved a new “quantum register,” or system of qubits, that appears to be robust over relatively long periods of time. The discovery, published today in the journal Nature, demonstrates that such wobbly qubits could be a promising foundation for future quantum computers.

A qubit represents a basic unit of quantum computing. Where a classical bit in today’s computers carries out a series of logical operations starting from one of either two states, 0 or 1, a qubit can exist in a superposition of both states. While in this delicate in-between state, a qubit should be able to simultaneously communicate with many other qubits and process multiple streams of information at a time, to quickly solve problems that would take classical computers years to process.

There are many types of qubits, some of which are engineered and others that exist naturally. Most qubits are notoriously fickle, either unable to maintain their superposition or unwilling to communicate with other qubits.

By comparison, the MIT team’s new qubit appears to be extremely robust, able to maintain a superposition between two vibrational states, even in the midst of environmental noise, for up to 10 seconds. The team believes the new vibrating qubits could be made to briefly interact, and potentially carry out tens of thousands of operations in the blink of an eye.

“We estimate it should take only a millisecond for these qubits to interact, so we can hope for 10,000 operations during that coherence time, which could be competitive with other platforms,” says Martin Zwierlein, the Thomas A. Frank Professor of Physics at MIT. “So, there is concrete hope toward making these qubits compute.”

Zwierlein is a co-author on the paper, along with lead author Thomas Hartke, Botond Oreg, and Ningyuan Jia, who are all members of MIT’s Research Laboratory of Electronics.

quibits shaking

Happy accidents

The team’s discovery initially happened by chance. Zwierlein’s group studies the behavior of atoms at ultracold, super-low densities. When atoms are chilled to temperatures a millionth that of interstellar space, and isolated at densities a millionth that of air, quantum phenomena and novel states of matter can emerge.

Under these extreme conditions, Zwierlein and his colleagues were studying the behavior of fermions. A fermion is technically defined as any particle that has an odd half-integer spin, like neutrons, protons, and electrons. In practical terms, this means that fermions are prickly by nature. No two identical fermions can occupy the same quantum state — a property known as the Pauli exclusion principle. For instance, if one fermion spins up, the other must spin down.

Electrons are classic examples of fermions, and their mutual Pauli exclusion is responsible for the structure of atoms and the diversity of the periodic table of elements, along with the stability of all the matter in the universe. Fermions are also any type of atom with an odd number of elementary particles, as these atoms would also naturally repel each other.

Zwierlein’s team happened to be studying fermionic atoms of potassium-40. They cooled a cloud of fermions down to 100 nanokelvins and used a system of lasers to generate an optical lattice in which to trap the atoms. They tuned the conditions so that each well in the lattice trapped a pair of fermions. Initially, they observed that under certain conditions, each pair of fermions appeared to move in sync, like a single molecule.

To probe this vibrational state further, they gave each fermion pair a kick, then took fluorescence images of the atoms in the lattice, and saw that every so often, most squares in the lattice went dark, reflecting pairs bound in a molecule. But as they continued imaging the system, the atoms seemed to reappear, in periodic fashion, indicating that the pairs were oscillating between two quantum vibrational states.

“It’s often in experimental physics that you have some bright signal, and the next moment it goes to hell, to never come back,” Zwierlein says. “Here, it went dark, but then bright again, and repeating. That oscillation shows there is a coherent superposition evolving over time. That was a happy moment.”

A low hum

After further imaging and calculations, the physicists confirmed that the fermion pairs were holding a superposition of two vibrational states, simultaneously moving together, like two pendula swinging in sync, and also relative to, or against each other.

“They oscillate between these two states at about 144 hertz,” Hartke notes. “That’s a frequency you could hear, like a low hum.”

The team was able to tune this frequency, and control the vibrational states of the fermion pairs, by three orders of magnitude, by applying and varying a magnetic field, through an effect known as Feshbach resonance.

“It’s like starting with two noninteracting pendula, and by applying a magnetic field, we create a spring between them, and can vary the strength of that spring, slowly pushing the pendula apart,” Zwierlein says.

In this way, they were able to simultaneously manipulate about 400 fermion pairs. They observed that as a group, the qubits maintained a state of superposition for up to 10 seconds, before individual pairs collapsed into one or the other vibrational state.

“We show we have full control over the states of these qubits,” Zwierlein says.

To make a functional quantum computer using vibrating qubits, the team will have to find ways to also control individual fermion pairs — a problem the physicists are already close to solving. The bigger challenge will be finding a way for individual qubits to communicate with each other. For this, Zwierlein has some ideas.

“This is a system where we know we can make two qubits interact,” he says. “There are ways to lower the barrier between pairs, so that they come together, interact, then split again, for about one millisecond. So, there is a clear path toward a two-qubit gate, which is what you would need to make a quantum computer.”

This research was supported, in part, by the National Science Foundation, the Gordon and Betty Moore Foundation, the Vannevar Bush Faculty Fellowship, and the Alexander von Humboldt Foundation.

© Credit: Sampson Wilcox/RLE

MIT researchers have found a way to store quantum information in the vibrational motion of atom pairs, similar to the swinging motion of two pendula, connected by a spring. The quantum register contains hundreds of pairs of vibrating qubits that researchers can coherently control for over ten seconds.

Microsoft is harnessing the power of the cloud to make the promise of quantum at scale a reality

8 March 2023 at 17:00

Today, Microsoft announced a significant quantum advancement and made our new Integrated Hybrid feature in Azure Quantum available to the public. This new functionality enables quantum and classical compute to integrate seamlessly together in the clouda first for our industry and an important step forward on our path to quantum at scale. Now, researchers can begin developing hybrid quantum applications with a mix of classical and quantum code together that run on one of today's quantum machines, Quantinuum, in Azure Quantum.

An infographic with a 3-part Venn Diagram; the top circle is labeled "Artificial Intelligence" with a brain icon, the lower left-hand circle is labeled 'Quantum Computing" with a connector icon, and the lower right-hand corner is labeled "HPC Automation" with a gear icon.

Classical computing has come a long way over the past century to be extraordinarily versatile and has transformed every industry. Even though it will continue to advance, there are certain problems it will never be able to solve. For computational problems that require closely modeling the phenomena of quantum physics, quantum computers will complement classical computers, creating a hybrid architecture that leverages the best characteristics of each design.

The quantum industry has long understood that quantum computing will always be a hybrid of classical and quantum compute. In fact, it was a key discussion point during this week's annual American Physical Society (APS) March Meeting in Las Vegas. However, our industry is just starting to grapple with, and design for, the future of hybrid classical and quantum compute at scale in the public cloud. At Microsoft, we are architecting a public cloud with Azure that enables scaled quantum computing to become a reality and then seamlessly delivers the profound benefits of it to our customers. In essence, AI, high-performance computing, and quantum are being co-designed as part of Azure, and this integration will have an impact in three important and surprising ways in the future.

1. The power of the cloud will unlock scaled quantum computing

Quantum at scale is required for scientists to help solve the hardest, most intractable problems our society faces, like reversing climate change and addressing food insecurity. Based on what we know todaylargely through our resource estimation work, a machine capable of solving such problems will require at least one million stable and controllable qubits. Microsoft is making progress on a machine capable of this scale every day.

A fundamental part of our plan to reach scale is to integrate our quantum machine alongside supercomputing classical machines in the cloud. A driving force of this design is the reality that the power of the cloud is required to run a fault-tolerant quantum machine. Achieving fault tolerance requires advanced error correction techniques, which basically means making logical qubits from physical qubits. While our unique topological qubit design will greatly enhance our machine's fault tolerance, advanced software and tremendous compute power will still be required to keep the machine stable.

In fact, to achieve fault tolerance, our quantum machine will be integrated with peta-scale classical compute in Azure and be able to handle bandwidths between quantum and classical that exceed 10-100 terabits per second. At every logical clock cycle of the quantum computer, we need this back and forth with classical computers to keep the quantum computer “alive” and yielding a reliable output solution. You may be surprised with this throughput requirement, but what fault tolerance means for quantum computing at scale is that a machine has to be able to perform a quintillion operations while making at most one error.

To put this number into perspective, imagine each operation was a grain of sand. Then for the machine to be fault tolerant, only a few grains of sand out of every grain of sand on earth could be faulty. Clearly, this type of scale is only enabled by the cloud, making Azure both a key enabler and differentiator of Microsoft's strategy to bring quantum at scale to the world.

2. The rise of classical compute capabilities in the cloud can help scientists solve quantum mechanical problems today

An incredible benefit of the rise of classical public cloud services is that scientists are able to achieve more at lower costs right now through the power of the cloud. For example, scientists from Microsoft, ETH Zurich, and the Pacific Northwest National Laboratory have recently presented a new automated workflow to leverage the scale of Azure to transform R&D processes in quantum chemistry and materials science. By optimizing the classical simulation code and re-factoring it to be cloud-native, the team achieved 10 times cost reduction for the simulation of a catalytic chemical reaction. These benefits will continue to grow as classical compute capabilities across the cloud advance even further.

Increasingly, we see great potential for high-performance computing and AI to accelerate advancements in chemistry and materials science. Near term, Azure will empower R&D teams with scale and speed. And long term, when we bring our scaled quantum machine to Azure, it will enable greater accuracy in modeling new pharmaceuticals, chemicals, and materials. The opportunity to unlock progress and growth is tremendous when you consider that chemistry and materials science impact 96 percent of manufactured goods and 100 percent of humanity. The key is to move to Azure now to both accelerate progress and future-proof your investments, as Azure is the home of Microsoft's incredible AI and high-performance computing capabilities today, and for our scaled quantum machine in the future.

3. A hyperscale cloud with AI, HPC, and quantum will create unprecedented opportunities for innovators

It is only when a quantum machine is designed alongside of, and integrated with, the AI supercomputers and scale of Azure, that we will be able to realize the greatest impacts from computing. With Azure, innovators will be able to design and execute a new class of impactful cloud applications that seamlessly bring together AI, HPC, and quantum at scale. For example, imagine the impactful applications in the future that will enable researchers with the scale of AI to sort through massive data sets, the insights from HPC to narrow down options, and the power of quantum at scale to improve model accuracy. These scenarios will only be possible in one application because of the seamless integration of HPC, AI, and quantum in Azure. Realizing this unprecedented opportunity requires advancing this deep integration in Azure today. As we bring HPC and AI together for advanced capabilities, we are also expanding the classical and quantum integration available right now.

Today, Microsoft took a significant step forward towards this vision by making our new Integrated Hybrid feature in Azure Quantum available to the public.

The ability to develop hybrid quantum applications with a mix of classical and quantum code together will empower today's quantum innovators to create a new class of algorithms. For example, now developers can build algorithms with adaptive phase estimation that can take advantage of performing classical computation, and iterate and adapt while physical qubits are coherent. Students can start learning algorithms without drawing circuits, and by leveraging high-level programming constructs such as branching based on qubits measurements (if statements), loops (for), calculations, and function calls. Additionally, scientists can now more easily explore ways to advance quantum error correction at the physical level on real hardware. Taken together, a new generation of quantum algorithms and protocols that could only be described in scientific papers can now run elegantly on quantum hardware in the cloud. A major milestone on the journey to scaled quantum computing has been achieved. 

Learn more about Azure Quantum

Azure is the place where all of this innovation comes together, ensuring your investments are future-proof. It's the place to be quantum-ready and quantum-safe, and as the cloud scales, so will your opportunity for impact. Please join Mark Russinovich, Chief Technology Officer and Technical Fellow of Azure at Microsoft, and me as we explore the future of the cloud in an upcoming Microsoft Quantum Innovation Series event.

A static image with headshots of Dr. Krysta Svore and Mark Russinovich above copy stating: “How will a hybrid of classical and quantum compute in the cloud enable a new class of applications?” The image describes the Microsoft Quantum Innovation Series event on May 16, 2023.

The post Microsoft is harnessing the power of the cloud to make the promise of quantum at scale a reality appeared first on Microsoft Azure Quantum Blog.

Tiny materials lead to a big advance in quantum computing

Like the transistors in a classical computer, superconducting qubits are the building blocks of a quantum computer. While engineers have been able to shrink transistors to nanometer scales, however, superconducting qubits are still measured in millimeters. This is one reason a practical quantum computing device couldn’t be miniaturized to the size of a smartphone, for instance.

MIT researchers have now used ultrathin materials to build superconducting qubits that are at least one-hundredth the size of conventional designs and suffer from less interference between neighboring qubits. This advance could improve the performance of quantum computers and enable the development of smaller quantum devices.

The researchers have demonstrated that hexagonal boron nitride, a material consisting of only a few monolayers of atoms, can be stacked to form the insulator in the capacitors on a superconducting qubit. This defect-free material enables capacitors that are much smaller than those typically used in a qubit, which shrinks its footprint without significantly sacrificing performance.

In addition, the researchers show that the structure of these smaller capacitors should greatly reduce cross-talk, which occurs when one qubit unintentionally affects surrounding qubits.

“Right now, we can have maybe 50 or 100 qubits in a device, but for practical use in the future, we will need thousands or millions of qubits in a device. So, it will be very important to miniaturize the size of each individual qubit and at the same time avoid the unwanted cross-talk between these hundreds of thousands of qubits. This is one of the very few materials we found that can be used in this kind of construction,” says co-lead author Joel Wang, a research scientist in the Engineering Quantum Systems group of the MIT Research Laboratory for Electronics.

Wang’s co-lead author is Megan Yamoah ’20, a former student in the Engineering Quantum Systems group who is currently studying at Oxford University on a Rhodes Scholarship. Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics, is a corresponding author, and the senior author is William D. Oliver, a professor of electrical engineering and computer science and of physics, an MIT Lincoln Laboratory Fellow, director of the Center for Quantum Engineering, and associate director of the Research Laboratory of Electronics. The research is published today in Nature Materials.

Qubit quandaries

Superconducting qubits, a particular kind of quantum computing platform that uses superconducting circuits, contain inductors and capacitors. Just like in a radio or other electronic device, these capacitors store the electric field energy. A capacitor is often built like a sandwich, with metal plates on either side of an insulating, or dielectric, material.

But unlike a radio, superconducting quantum computers operate at super-cold temperatures — less than 0.02 degrees above absolute zero (-273.15 degrees Celsius) — and have very high-frequency electric fields, similar to today’s cellphones. Most insulating materials that work in this regime have defects. While not detrimental to most classical applications, when quantum-coherent information passes through the dielectric layer, it may get lost or absorbed in some random way.

“Most common dielectrics used for integrated circuits, such as silicon oxides or silicon nitrides, have many defects, resulting in quality factors around 500 to 1,000. This is simply too lossy for quantum computing applications,” Oliver says.

To get around this, conventional qubit capacitors are more like open-faced sandwiches, with no top plate and a vacuum sitting above the bottom plate to act as the insulating layer.

“The price one pays is that the plates are much bigger because you dilute the electric field and use a much larger layer for the vacuum,” Wang says. “The size of each individual qubit will be much larger than if you can contain everything in a small device. And the other problem is, when you have two qubits next to each other, and each qubit has its own electric field open to the free space, there might be some unwanted talk between them, which can make it difficult to control just one qubit. One would love to go back to the very original idea of a capacitor, which is just two electric plates with a very clean insulator sandwiched in between.”

So, that’s what these researchers did.

They thought hexagonal boron nitride, which is from a family known as van der Waals materials (also called 2D materials), would be a good candidate to build a capacitor. This unique material can be thinned down to one layer of atoms that is crystalline in structure and does not contain defects. Researchers can then stack those thin layers in desired configurations.

To test hexagonal boron nitride, they ran experiments to characterize how clean the material is when interacting with a high-frequency electric field at ultracold temperatures, and found that very little energy is lost when it passes through the material.

“Much of the previous work characterizing hBN (hexagonal boron nitride) was performed at or near zero frequency using DC transport measurements. However, qubits operate in the gigahertz regime. It’s great to see that hBN capacitors have quality factors exceeding 100,000 at these frequencies, amongst the highest Qs I have seen for lithographically defined, integrated parallel-plate capacitors,” Oliver says.

Capacitor construction

They used hexagonal boron nitride to build a parallel-plate capacitor for a qubit. To fabricate the capacitor, they sandwiched hexagonal boron nitride between very thin layers of another van der Waals material, niobium diselenide.

The intricate fabrication process involved preparing one-atom-thick layers of the materials under a microscope and then using a sticky polymer to grab each layer and stack it on top of the other. They placed the sticky polymer, with the stack of 2D materials, onto the qubit circuit, then melted the polymer and washed it away.

Then they connected the capacitor to the existing structure and cooled the qubit to 20 millikelvins (-273.13 C).  

“One of the biggest challenges of the fabrication process is working with niobium diselenide, which will oxidize in seconds if it is exposed to the air. To avoid that, the whole assembly of this structure has to be done in what we call the glove box, which is a big box filled with argon, which is an inert gas that contains a very low level of oxygen. We have to do everything inside this box,” Wang says.

The resulting qubit is about 100 times smaller than what they made with traditional techniques on the same chip. The coherence time, or lifetime, of the qubit is only a few microseconds shorter with their new design. And capacitors built with hexagonal boron nitride contain more than 90 percent of the electric field between the upper and lower plates, which suggests they will significantly suppress cross-talk among neighboring qubits, Wang says. This work is complementary to recent research by a team at Columbia University and Raytheon.

In the future, the researchers want to use this method to build many qubits on a chip to verify that their technique reduces cross-talk. They also want to improve the performance of the qubit by finetuning the fabrication process, or even building the entire qubit out of 2D materials.

“Now we have cleared a path to show that you can safely use as much hexagonal boron nitride as you want without worrying too much about defects. This opens up a lot of opportunity where you can make all kinds of different heterostructures and combine it with a microwave circuit, and there is a lot more room that you can explore. In a way, we are giving people the green light — you can use this material in any way you want without worrying too much about the loss that is associated with the dielectric,” Wang says.

This research was funded, in part, by the U.S. Army Research Office, the National Science Foundation, and the Assistant Secretary of Defense for Research and Engineering via MIT Lincoln Laboratory.

© Image: Figure courtesy of the researcher; edited by Christine Daniloff and Jose-Luis Olivares, MIT.

MIT researchers used the 2D material hexagonal boron nitride to build much smaller capacitors for superconducting qubits, enabling them to shrink the footprint of a qubit by two orders of magnitude without sacrificing performance.