Research, teaching and outreach in Physics at UW–Madison
Thad Walker honored with Vilas Distinguished Achievement Professorship
Extraordinary members of the University of Wisconsin–Madison faculty, including physics professor Thad Walker, have been honored during the last year with awards supported by the estate of professor, U.S. senator and UW Regent William F. Vilas (1840-1908).
Walker was one of seventeen professors were named to Vilas Distinguished Achievement Professorships, an award recognizing distinguished scholarship as well as standout efforts in teaching and service. The professorship provides five years of flexible funding — two-thirds of which is provided by the Office of the Provost through the generosity of the Vilas trustees and one-third provided by the school or college whose dean nominated the winner.
In addition, nine professors received Vilas Faculty Mid-Career Investigator Awards and six professors received Vilas Faculty Early Career Investigator Awards.
Alex Levchenko awarded NSF condensed matter and materials theory grant
This award supports theoretical research on quantum materials where the strong electron-electron interaction leads to unique transport, thermodynamic and magnetic properties. The research agenda addresses both fundamental physics of electronic interactions in complex materials and practical physics of mesoscopic devices relevant for applications in the domain of quantum science with micro and nanostructures.
The conversion of heat into electricity in solid state systems is governed by thermoelectric effects. The thermoelectric transport in quantum materials and devices is at the heart of various modern electronics applications. Over the last decade, transport measurements in atomically thin two-dimensional materials, such as graphene composed of a single layer of carbon atoms, provided overwhelming evidence that the flow of electrons in such systems exhibits hydrodynamic behavior that resembles the flow of a viscous fluid. These advances pushed the limits of hydrodynamics, providing new perspectives on old fundamental problems and opening doors for completely new discoveries of emergent physics phenomena. This project is, in part, devoted to new research on thermoelectric resistance of such systems as they are subjected to magnetic fields. The PI will also extend these studies to other forms of low-temperature electronic behavior in solids such as superconductivity, where electrons flow without any resistance, and magnetism, as well as their coexistence.
This award also supports the PI’s educational and outreach activities. The project places significant emphasis on training graduate and undergraduate students by engaging them in research in a highly collaborative environment with a postdoctoral scholar and colleagues from other groups. The PI will reach out to the public and high-school student audiences through (i) collaboration with the USA Physics Olympiad team to foster new generation of physicists and train high-school students for international scholastic competition and (ii) public education via entertaining Wonders of Physics shows. The PI will also be involved in the scientific coordination of a physics summer school as well as organization of international conferences and workshops.
UW–Madison celebrates the first World Quantum Day, April 14
Even quantum physicists do not understand quantum physics, or so the saying* goes.
“The worst grade I ever got in any class was my first quarter of quantum mechanics, because it just was weird and I didn’t understand it and I couldn’t get my head around it,” says Shimon Kolkowitz, a UW–Madison physics professor with the Wisconsin Quantum Institute (WQI), who now conducts research in quantum sensing. “It is something you develop some kind of feeling and intuition for over time, so it’s my personal feeling, and the feeling of many, that it’s important to start exposing people to these concepts much earlier [than in college].”
Quantum science is weird because it explains the workings of our world at the sub-atomic level. The classical physical world we experience and understand — the predictable trajectory of a baseball in the air or the Earth rotating around the sun — breaks down at these tiny scales.
Understand it or not, quantum science is here to stay.
“Quantum science is a rapidly-growing area of research and industry, and it’s going to have a number of major impacts on any number of different areas of commerce,” Kolkowitz says. “There’s a huge need to train a growing quantum workforce that can participate in, engage with, and develop these new technologies.”
The first-ever World Quantum Day, to be celebrated annually on April 14, is an international, community driven event to spark interest and generate enthusiasm for quantum mechanics. A goal of World Quantum Day is to promote public awareness of the positive impact quantum science has had and will have on society. [The date is taken from Planck’s constant, 4.14 * 10-15 eV · s, a value that is used in many quantum mechanics equations.]
“It’s a day to engage people in quantum science and let them know what is going on in current research, but it’s also a chance to demystify and make quantum science more accessible and available,” says Mallory Conlon, a quantum science outreach coordinator at UW–Madison.
Conlon is working with QuanTime, an educational initiative developed by leading quantum institutions to introduce quantum activities to middle and high school students. Anyone can play QuanTime’s online games, where they will learn about principals such as entanglement and superposition. There is even a quantum chess game.
“We also have Wonders of Quantum Physics electron transition kits, and we’re sending out nearly 1000 kits to classrooms across the country,” Conlon says. “It’s an inquiry-based activity where participants learn how we can use light to manipulate atoms and electrons, which is really the underpinnings of how quantum computers work.”
The physics department and WQI will also be celebrating WQD by highlighting several quantum science researchers and sharing the top five quantum stories from the past year on social media. Follow along on Twitter and Instagram (both @UWMadPhysics) to learn more about the exciting quantum research being done at UW–Madison.
UW–Madison and WQI are members of the Chicago Quantum Exchange, the NSF-funded Quantum Leap Challenge Institute HQAN, and the Department of Energy’s National Quantum Information Science (QIS) Research Center Q-NEXT, three collaborative efforts that are advancing quantum information science and engineering, especially in Great Lakes region. Learn more about the research happening across our collaborations by searching #MidwestQuantum on social media.
* Borrowed from quantum physicist Richard Feynman’s quote: “I think I can safely say that nobody understands quantum mechanics.”
Ultraprecise atomic clock poised for new physics discoveries
Their instrument, known as an optical lattice atomic clock, can measure differences in time to a precision equivalent to losing just one second every 300 billion years and is the first example of a “multiplexed” optical clock, where six separate clocks can exist in the same environment. Its design allows the team to test ways to search for gravitational waves, attempt to detect dark matter, and discover new physics with clocks.
“Optical lattice clocks are already the best clocks in the world, and here we get this level of performance that no one has seen before,” says Shimon Kolkowitz, a UW–Madison physics professor and senior author of the study. “We’re working to both improve their performance and to develop emerging applications that are enabled by this improved performance.”
Atomic clocks are so precise because they take advantage of a fundamental property of atoms: when an electron changes energy levels, it absorbs or emits light with a frequency that is identical for all atoms of a particular element. Optical atomic clocks keep time by using a laser that is tuned to precisely match this frequency, and they require some of the world’s most sophisticated lasers to keep accurate time.
By comparison, Kolkowitz’s group has “a relatively lousy laser,” he says, so they knew that any clock they built would not be the most accurate or precise on its own. But they also knew that many downstream applications of optical clocks will require portable, commercially available lasers like theirs. Designing a clock that could use average lasers would be a boon.
Shimon Kolkowitz one of four UW professors awarded Sloan Fellowship
Four University of Wisconsin–Madison professors, including assistant professor of physics Shimon Kolkowitz, have been named to Sloan Research Fellowships — competitive, prestigious awards given to promising researchers in the early stages of their careers.
“Today’s Sloan Research Fellows represent the scientific leaders of tomorrow,” says Adam F. Falk, president of the Alfred P. Sloan Foundation, which has awarded the fellowships since 1955. “As formidable young scholars, they are already shaping the research agenda within their respective fields—and their trailblazing won’t end here.”
Kolkowitz, an assistant professor of physics, builds some of the most precise clocks in the world by trapping ultracold atoms of strontium — clocks so accurate they could be used to test fundamental theories of physics and search for dark matter.
UW–Madison’s other 2022 Sloan Fellows are Tatyana Shcherbina (math), Zachary K. Wickens (chemistry) and Andrew Zimmer (math).
The UW–Madison professors are among 118 researchers from the United States and Canada honored by the New York-based philanthropic foundation. The four new fellows join 110 UW–Madison researchers honored in the past.
Each fellow receives $75,000 in research funding from the foundation, which awards Sloan Research Fellowships in eight scientific and technical fields: chemistry, computer science, economics, mathematics, computational and evolutionary molecular biology, neuroscience, ocean sciences and physics.
Shimon Kolkowitz earns NSF CAREER award
Shimon Kolkowitz has already developed one of the most precise atomic clocks ever. Now, the UW–Madison physics professor has been awarded a Faculty Early Career Development (CAREER) award from the National Science Foundation (NSF) to use his atomic clocks to potentially answer some big questions about the physics of our universe.
The five-year, $800,000 in total award will cover research expenses, graduate student support, and outreach projects based on the research.
“I am honored and proud to receive an NSF CAREER award, which will help my research group expand our experimental efforts and build upon our recent results,” Kolkowitz says. “This award will support research into new ways to harness the remarkable precision of optical atomic clocks for exciting physics applications such as searching for dark matter and detecting gravitational waves.”
Atomic clocks are so precise because they take advantage of the natural vibration frequencies of atoms, which are identical for all atoms of a particular element. Kolkowitz and his research group have developed atomic clocks that can detect the difference in these frequencies between two clocks that would only disagree with each other by one second after 300 billion years, the tiniest detectable frequency changes to date. These clocks, then, can measure effects that shifts their frequency by only 0.00000000000000001%, opening the possibility of using them in the search for new physics.
A significant advancement in Kolkowitz’s clocks is that they are multiplexed, with six or more separate clocks in one
vacuum chamber, effectively placing each clock in the same environment. Mutliplexing means that comparisons between the clocks, and not their individual accuracy, is what matters — and allows the group to use commercially available, robust and portable lasers in their measurements. Though the clocks are not yet ready to be used to detect gravitational waves, Kolkowitz says the current setup “looks a bit like how you would eventually do that,” and will allow him to test out and demonstrate the concept.
In the spirit of the Wisconsin Idea and the NSF’s “broader impacts” to benefit society beyond scientific merit, with this award, Kolkowitz will focus efforts on quantum science outreach with pre-college students.
“We’ll be developing new demos and hands-on activities designed to introduce K-12 students to modern physics concepts,” Kolkowitz says. “We’ll use these activities to engage students at live shows and interactive events as part of The Wonders of Physics outreach program, with an emphasis on reaching rural and Native American communities in Wisconsin.”
NSF established these awards to help scientists and engineers develop simultaneously their contributions to research and education early in their careers. CAREER funds are awarded by the federal agency to junior-level faculty at colleges and universities.
Undergraduate quantum science research fellowship launches
The Open Quantum Initiative (OQI), a working group of students, researchers, educators, and leaders across the Chicago Quantum Exchange (CQE), announced the launch of the OQI Undergraduate Fellowship as part of their effort to advocate for and contribute to the development of a diverse and inclusive quantum workforce.
The primary mission of the OQI is to champion the development of a more inclusive quantum community. Science, technology, engineering, and mathematics (STEM) fields remain overwhelmingly white and male—only about 20% of bachelor’s degrees in physics, engineering, and computer science go to women, a mere 6% of all STEM bachelor’s degrees are awarded to African American students, and 12% of all STEM bachelor’s degrees are awarded to Hispanic students. But as the field of quantum science is still relatively new compared to other STEM subjects, groups like the OQI see a chance to make the foundations of the field diverse and accessible to all from the start.
“In many respects, we are building a national workforce from the ground up,” says David Awschalom, the Liew Family Professor in Molecular Engineering and Physics at the University of Chicago, senior scientist at Argonne National Laboratory, director of the Chicago Quantum Exchange, and director of Q-NEXT, a Department of Energy quantum information science center led by Argonne. “There are incredible opportunities here to make the field of quantum engineering as inclusive and equitable as possible from the very beginning, creating a strong ecosystem for the future.”
At the heart of the OQI’s effort is a new fellowship starting in summer 2022. For 10 weeks, fellows will live and work at a CQE member or partner institution, completing a research project in quantum information science and engineering under the guidance of a mentor. Students will have numerous opportunities to interact with the other fellows in their cohort during the summer research period and throughout the following academic year.
Through this fellowship, the students can expand their understanding of quantum science, receive career guidance, and grow their professional networks with leaders in academia and industry. The OQI will also aim to provide future research experiences in subsequent summers, as well as provide opportunities to mentor future fellows, helping to build a larger, diverse quantum community over time.
With the support of CQE’s member and partner institutions, including the University of Chicago, Argonne, Fermilab, University of Illinois Urbana-Champaign, University of Wisconsin-Madison, Northwestern University, and The Ohio State University, along with the NSF Quantum Leap Challenge Institute for Hybrid Quantum Architectures and Networks (HQAN) and Q-NEXT, this fellowship helps to establish diversity, equity, and inclusion as priorities central to the development of the quantum ecosystem.
The OQI launched the fellowship alongside a workshop on September 22 and 23. The OQI workshop, titled “Building a Diverse Quantum Ecosystem,” brought together CQE students, researchers, and professionals from across different institutions, including industry, to discuss the prevailing issues and barriers in quantum information science as the field develops. Institutional changemakers also shared what they have learned from their own efforts to increase representation. A panel on education and workforce development at the upcoming Chicago Quantum Summit on Nov. 4 will continue the discussion on building inclusive onramps for the quantum information science field.
“For quantum science and engineering to achieve its full potential, it must be accessible to all,” says Kayla Lee, Academic Alliance Lead at IBM Quantum and keynote speaker of the OQI workshop. “The OQI Undergraduate Fellowship provides explicit support for historically marginalized communities, which is crucial to increasing quantum engagement in a way that creates a more diverse and equitable field.”
Applications for the OQI Undergraduate Fellowship are open now.
New 3D integrated semiconductor qubit saves space without sacrificing performance
Small but mighty, semiconducting qubits are a promising area of research on the road to a fully functional quantum computer. Less than one square micron, thousands of these qubits could fit into the space taken up by one of the current industry-leading superconducting qubit platforms, such as IBM’s or Google’s.
For a quantum computer on the order of tens or hundreds of qubits, that size difference is insignificant. But to get to the millions or billions of qubits needed to use these computers to model quantum physical processes or fold a protein in a matter of minutes, the tiny size of the semiconducting qubits could become a huge advantage.
Except, says Nathan Holman, who graduated from UW–Madison physics professor Mark Eriksson’s group with a PhD in 2020 and is now a scientist with HRL Laboratories, “All those qubits need to be wired up. But the qubits are so small, so how do we get the lines in there?”
In a new study published in NPJ Quantum Information on September 9, Holman and colleagues applied flip chip bonding to 3D integrate superconducting resonators with semiconducting qubits for the first time, freeing up space for the control wires in the process. They then showed that the new chip performs as well as non-integrated ones, meaning that they solved one problem without introducing another.
If quantum computers are to have any chance of outperforming their classical counterparts, their individual qubit units need to be scalable so that millions of qubits can work together. They also need an error correction scheme such as the surface code, which requires a 2D qubit grid and is the current best-proposed scheme.
To attain any 2D tiled structure with current semiconducting devices, it quickly gets to the point where 100% of available surface area is covered by wires — and at that point, it is physically impossible to expand the device’s capacity by adding more qubits.
To try to alleviate the space issue, the researchers applied a 3D integration method developed by their colleagues at MIT. Essentially, the process takes two silicon dies, attaches pillars of the soft metal indium placed onto one, aligns the two dies, and then presses them together. The result is that the wires come in from the top instead of from the side.
“The 3D integration helps you get some of the wiring in in a denser way than you could with the traditional method,” Holman says. “This particular approach has never been done with semiconductor qubits, and I think the big reason why it hadn’t is that it’s just a huge fabrication challenge.”
In the second part of their study, the researchers needed to confirm that their new design was functional — and that it didn’t add disadvantages that would negate the spacing success.
The device itself has a cavity with a well-defined resonant frequency, which means that when they probe it with microwave photons at that frequency, the photons transmit through the cavity and are registered by a detector. The qubit itself is coupled to the cavity, which allows the researchers to determine if it is functioning or not: a functioning qubit changes the resonant frequency, and the number of photons detected goes down.
They probed their 3D integrated devices with the microwave photons, and when they expected their qubits to be working, they saw the expected signal. In other words, the new design did not negatively affect device performance.
“Even though there’s all this added complexity, the devices didn’t perform any worse than devices that are easier to make,” Holman says. “I think this work makes it conceivable to go to the next step with this technology, whereas before it was very tricky to imagine past a certain number of qubits.”
Holman emphasizes that this work does not solve all the design and functionality issues currently hampering the success of fully functional quantum computers.
“Even with all the resources and large industry teams working on this problem, it is non-trivial,” Holman says. “It’s exciting, but it’s a long-haul excitement. This work is one more piece of the puzzle.”
The article reports that this work was sponsored in part by the Army Research Office (ARO) under Grant Number W911NF-17-1-0274 (at UW–Madison) and by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract No. FA8721-05-C-0002 (at MIT Lincoln Laboratory).
Flexible, easy-to-scale nanoribbons move graphene toward use in tech applications
From radio to television to the internet, telecommunications transmissions are simply information carried on light waves and converted to electrical signals.
Silicon-based fiber optics are currently the best structures for high-speed, long distance transmissions, but graphene — an all-carbon, ultra-thin and adaptable material — could improve performance even more.
In a study published April 16 in ACS Photonics, University of Wisconsin–Madison researchers fabricated graphene into the smallest ribbon structures to date using a method that makes scaling-up simple. In tests with these tiny ribbons, the scientists discovered they were closing in on the properties they needed to move graphene toward usefulness in telecommunications equipment.
“Previous research suggested that to be viable for telecommunication technologies, graphene would need to be structured prohibitively small over large areas, (which is) a fabrication nightmare,” says Joel Siegel, a UW–Madison graduate student in physics professor Victor Brar’s group and co-lead author of the study. “In our study, we created a scalable fabrication technique to make the smallest graphene ribbon structures yet and found that with modest further reductions in ribbon width, we can start getting to telecommunications range.”
The Office of the Vice Chancellor for Research and Graduate Education has announced 23 faculty winners of the Vilas Associates Competition, including physics professor Deniz Yavuz. The Vilas Associates Competition recognizes new and ongoing research of the highest quality and significance.
The award is funded by the William F. Vilas Estate Trust.
Recipients are chosen competitively by the divisional research committees on the basis of a detailed proposal. Winners receive up to two-ninths of research salary support (including the associated fringe costs) for both summers 2021 and 2022, as well as a $12,500 flexible research fund in each of the two fiscal years. Faculty paid on an annual basis are not eligible for the summer salary support but are eligible for the flexible fund portion of this award.