Research, teaching and outreach in Physics at UW–Madison
AMO
Mark Saffman named “Outstanding Referee” for American Physical Society journals
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Mark Saffman
Congrats to Prof. Mark Saffman on being named a 2026 Outstanding Referee of the American Physical Society journals!
The highly selective Outstanding Referee program annually recognizes about 150 of the roughly 56,000 referees who have been asked to review one or more papers in the last twelve months. Like Fellowship in the APS, this is a lifetime award.
In this year, 2026, 156 Outstanding Referees were selected. APS Editors select the honorees based on the quality, number, and timeliness of their reports, without regard for membership in the APS, country of origin, or field of research. Referees are rewarded for their work carried out since 1978, the earliest year for which we have accurate data on referee reports returned. The decisions are difficult and there are many excellent referees who are still to be recognized.
The Outstanding Referee program was instituted in 2008 to recognize scientists who have been exceptionally helpful in assessing manuscripts for publication in the APS journals. By means of the program, APS expresses its appreciation to all referees, whose efforts in peer review not only keep the standards of the journals at a high level, but in many cases also help authors to improve the quality and readability of their articles – even those that are not published by APS.
Other current UW–Madison physics department members who are recipients of this honor include Baha Balantekin (2024), Mark Friesen (2023), Lisa Everett (2021), Deniz Yavuz (2013), and Thad Walker (2009).
A Path to Scalable Quantum Computing with Faster Qubit Measurements and 99.93% Reliability
This post is derived from content originally published by the University of Toronto
Mark Saffman
Congrats to Mark Saffman, the Johannes Rydberg Professor of Physics and director of the Wisconsin Quantum Institute, on earning the ninth Biennial John Stewart Bell Prize for Research on Fundamental Issues in Quantum Mechanics and Their Applications.
He shares the prize with Antoine Browaeys (CNRS, Université Paris-Saclay) and Mikhail Lukin (Harvard) for their pioneering contributions to quantum simulation and quantum computing with neutral atoms in optical tweezer arrays, including the development of large-scale programmable arrays for scalable quantum computation. The prize will be given at the eleventh international conference on Quantum Information and Quantum Control, University of Toronto.
Saffman’s career-spanning work was also recognized last month with the American Physical Society’s Ramsey Prize in AMO Physics and in Precision Tests of Fundamental Laws and Symmetries, a prize he shares with Browaeys.
The John Stewart Bell Prize for Research on Fundamental Issues in Quantum Mechanics and their Applications (short form: “Bell Prize”) was established in 2009, and is awarded every other year, for significant contributions first published in the preceding 6 years. The award is meant to recognize major advances relating to the foundations of quantum mechanics and to the applications of these principles – this covers, but is not limited to, quantum information theory, quantum computation, quantum foundations, quantum cryptography, and quantum control. The award is not intended as a “lifetime achievement” award, but rather to highlight the continuing rapid pace of research in these areas, and the fruitful interplay of fundamental research and potential applications. It is intended to cover even-handedly both of these aspects, and to include both theoretical and experimental contributions.
Mark Saffman awarded 2026 APS Ramsey Prize
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Mark Saffman, the Johannes Rydberg Professor of Physics and director of the Wisconsin Quantum Institute, won the American Physical Society’s 2026 Norman F. Ramsey Prize in Atomic, Molecular, and Optical Physics, and in Precision Tests of Fundamental Laws and Symmetries.
The Ramsey prize recognizes outstanding accomplishments in the two fields of Norman Ramsey: atomic, molecular, and optical (AMO) physics; and precision tests of fundamental laws and symmetries. Saffman won “for seminal developments of quantum information processing with neutral atoms that allow the investigation of many-body problems that are intractable by classical computing.” He shares the prize with Antoine Browaeys at the Institut d’Optique in France.
Mark Saffman
Saffman joined the UW–Madison physics faculty in 1999 with ideas for his research program but struggled to acquire enough funding. Then, he started reading theory papers about the relatively new field of quantum computing and how to develop qubits, or quantum bits.
“This was in an era when people were proposing all these different ideas for qubits,” Saffman says. “I read this paper about using Rydberg gates to entangle atomic qubits and thought, ‘This looks interesting, let’s do that.’ That was the smartest decision I ever made in my career.”
An atom can be induced into a Rydberg state by a strong laser, when one of its outer shell electrons is excited into a very high energy state. The atom is effectively much larger than usual, and can lead to interesting quantum properties. Relatively inexperienced in experimental atomic physics, Saffman approached Thad Walker, a professor in the department and an expert on how to laser cool atoms, about collaborating. A decade later, they had their major success: a Rydberg blockade.
“The basic interaction is that you excite one atom to a Rydberg state and then you cannot excite a second one close by,” Saffman says. “That blockade interaction lies behind the ability to do a logic gate — a CNOT gate — and entangle two qubits.”
A year later, Saffman and Walker demonstrated the first CNOT gate for atomic qubits. These qubits, also called neutral atom qubits, quickly are now one of the leading platforms for achieving fault tolerant quantum computing.
Over the next decade Saffman started to realize that building a fully functional quantum computer was not just a scientific effort, it was a major engineering effort, one that was likely outside the scope of an academic research group.
“It became clear to me that to compete at the forefront, I needed more resources. I wanted to go faster,” Saffman says. “So, I ended up joining forces with ColdQuanta (now Infleqtion), an existing small cold atom sensing and components company .”
The glow of red and green lasers and an array of supporting electronics fill the Saffman lab | Jacob Scott, PhD’25
Saffman brought his quantum computing ideas to the company as Chief Scientist for Quantum Information at Colorado-based Infleqtion in 2018, and the company now has a satellite office in Madison.
The partnership with Infleqtion did, in fact, accelerate Saffman’s research. In 2022, his group, including long-time scientist and group member Trent Graham, co-authored a paper with engineers at Infleqtion where they demonstrated the first quantum algorithm to be run on an atomic quantum computer. It was a huge proof of principle and significant step forward in the field.
Quantum information research has emerged as a major topic within the AMO physics community. At UW–Madison, Saffman has been a key player in that shift. In 2019, he helped develop the Wisconsin Quantum Institute, an interdisciplinary effort of all quantum information science and engineering researchers on campus. That same year, he was named the institute’s director.
“UW–Madison was one of the first places to have multiple serious efforts in qubits: Thad and I pioneered neutral atoms, (physics professor) Mark Eriksson pioneered silicon spin qubits, (physics professor) Robert McDermott has superconducting qubits,” Saffman says. “Now, a huge fraction of new faculty coming out of academia and starting their own groups are working in quantum information-related science and engineering, including many of our new faculty. The state of quantum computing at UW–Madison is very strong.”
Welcome, Prof. Josiah Sinclair!
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Josiah Sinclair
When he was younger, UW–Madison assistant professor of physics Josiah Sinclair wanted to be a scientist-inventor when he grew up. In high school, he would ask questions in biology and chemistry classes that his teachers said were really physics questions. So, when he began his undergrad at Calvin University, he majored in physics, believing that experimental physics would be at the intersection of his interests. In the end, it was quantum physics that really fascinated him, motivating him to complete a PhD in experimental quantum optics and atomic physics at the University of Toronto. He says, “The ethos of my PhD group was this idea that with modern technology, maybe we can invent an apparatus that can reproduce the essential elements of this or that classic thought experiment and learn something new.” After completing a postdoc at MIT, Sinclair joined the UW–Madison physics department as an assistant professor in August, where he will tinker in the lab as an experimental quantum physicist, and just maybe invent a new kind of neutral atom quantum computer.
Please give an overview of your research.
There’s a global race underway to build a quantum computer—a machine that operates according to the laws of quantum mechanics and uses an entirely different, more powerful kind of logic to solve certain problems exponentially faster than any classical computer can. Quantum computers won’t solve all problems, but there’s strong confidence they’ll solve some very important ones. Moreover, as we build them, we’re likely to discover new applications we can’t yet imagine.
The approach my group focuses on uses arrays of single neutral atoms as qubits. Right now, the central challenge in practical quantum computing is how to scale up quantum processors without compromising their quality. Today’s atom-array quantum computers are remarkable, hand-built systems that have reached hundreds or even thousands of qubits in recent years—a truly impressive feat and possible in part due to pioneering work done right here in Madison. However, as these systems grow larger, we’re hitting fundamental size limits that call for new strategies.
My lab is working to develop modular interconnects for neutral-atom quantum computers. Instead of trying to build a single massive machine, we aim to link multiple smaller systems together using single photons traveling through optical fibers. The challenge is that single photons are easily misplaced, so to make this work, we need to develop the most efficient atom–photon interfaces ever built—pushing the limits of our ability to control the interaction between one atom and one photon.
Once we get these quantum links working, we’ll have realized the essential building block for a truly scalable quantum computer and maybe someday the quantum internet. Beyond computing, these technologies could also enable new kinds of distributed quantum sensors, where multiple quantum systems work together to detect extremely faint signals spread across a large area, like photons arriving from distant planets.
What are the one or two main projects your new group will work on?
Our main focus will be to build two neutral atom quantum processors in adjacent rooms and link them together with an optical fiber. This project will teach us how to integrate highly efficient photonic interfaces—such as optical cavities—with atom arrays, and how to precisely control the interactions between atoms and photons. Step by step, we aim to demonstrate atom-photon entanglement and eventually send quantum information back and forth through the fiber.
We’re collaborating with a new company called CavilinQ, a Harvard spin-out supported by Argonne National Lab, to integrate a new cavity design with the geometry we want to explore for atom-photon coupling. Because we intend to iterate rapidly on the cavity design, our setup will be built on a precision translation stage, allowing us to easily slide the system in and out and swap out cavity components.
Another project in the lab will focus on developing a new kind of cold-atom quantum sensor. Most current sensors rely on magneto-optical traps, which require bulky electromagnets and impose constraints that limit performance. We plan to explore magnetic-field-free trapping techniques that could lead to simpler, more compact, and ultimately higher-performance quantum sensors.
What attracted you to Madison and the university?
Well, for me professionally, Madison’s a powerhouse in atomic physics and quantum computing. There are groups here that have been highly influential since the beginning in developing neutral atoms as a platform for quantum information science. So there’s a strong atomic physics community here that has incredible overlap with my research interests, and a thriving broader quantum information community as well. Some people work best in isolation, but that is not who I am, so the prospects of joining this vibrant collaborative environment was very appealing to me.
I also really enjoyed all my interactions with the members of the search committee and other faculty here both during my interview and subsequent visits. On the personal side, my wife’s family is all in the Chicago area, so the prospects of being so close to one side of the family were very appealing. We have a 18-month-old daughter, and when we visited, we just had such a positive impression of Madison as a place to have a family and to grow up.
What is your favorite element and/or elementary particle?
It’s rubidium. I worked with it in my PhD, I worked with it in my postdoc, and I will work with it again. It’s simple. It has one electron in the outer valence shell, which makes it easy to work with. It was one of the first atoms to be laser cooled and one of the first to be Bose condensed, but I think it still has some tricks for us up its sleeve. I believe the first quantum computers are going to be built out of rubidium atoms. Some people (and companies) think we will need a more complicated atom, like strontium or ytterbium, but I think we already have the atom we need—we just need to figure out how to make it work.
What hobbies and interests do you have?
In the last year: spending time with my eighteen-month-old daughter. It’s been a special time. I also enjoy photography. I do some photography of research labs, but mostly I do adventure photography. I don’t think of myself as a particularly talented photographer, my specialty is more being willing to lug a heavy camera up a mountain. I also really enjoy cycling, rock climbing, reading, and traveling.
Deniz Yavuz elected Fellow of the American Physical Society
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Deniz Yavuz
Congratulations to Prof. Deniz Yavuz, who was elected a 2025 Fellow of the American Physical Society!
He was elected “for outstanding experimental and theoretical contributions to nanoscale localization of atoms with electromagnetically induced transparency and collective radiation effects in atomic ensembles,” and nominated by the Division of Atomic, Molecular & Optical Physics (DAMOP).
APS Fellowship is a distinct honor signifying recognition by one’s professional peers for outstanding contributions to physics. Each year, no more than one half of one percent of the Society’s membership is recognized by this honor.
The Office of the Vice Chancellor for Research (OVCR) hosts the Research Forward initiative to stimulate and support highly innovative and groundbreaking research at the University of Wisconsin–Madison. The initiative is supported by the Wisconsin Alumni Research Foundation (WARF) and will provide funding for 1–2 years, depending on the needs and scope of the project.
Research Forward seeks to support collaborative, multidisciplinary, multi-investigator research projects that are high-risk, high-impact, and transformative. It seeks to fund research projects that have the potential to fundamentally transform a field of study as well as projects that require significant development prior to the submission of applications for external funding. Collaborative research proposals are welcome from within any of the four divisions (Arts & Humanities, Biological Sciences, Physical Sciences, Social Sciences), as are cross-divisional collaborations.
Physics professor Mark Saffman is part of a team awarded funding in Round 4 of the Research Forward competition for their project:
Quanta sensing for next generation quantum computing
Future quantum computers could open new scientific and engineering frontiers, impacting existential challenges like climate change. However, quantum information is delicate; it leaks with time and is prone to significant errors. These errors are exacerbated by imperfect reading and writing of quantum bits (qubits). These challenges fundamentally limit our ability to run quantum programs, and could hold back this powerful technology. Fast and accurate qubit readout, therefore, is essential for unlocking the quantum advantage. Current quantum computers use conventional cameras for reading qubits, which are inherently slow and noisy.
This research project will use quanta (single-photon) sensors for fast and accurate qubit readout. Quanta sensors detect individual photons scattered from qubits, thus enabling sensing qubits at 2-3 orders of magnitude higher speeds (few microseconds from ~10 milliseconds), thereby transforming the capabilities (speed, accuracy) of future quantum computers, and for the first time, paving the way for scalable and practical quantum computing.
Principal investigator: Mohit Gupta, associate professor of computer sciences
Co-PIs: Mark Saffman, professor of physics; Swamit Tannu, assistant professor of computer sciences; Andreas Velten, associate professor of biostatistics and medical informatics, electrical and computer engineering
Welcome, Professor Matthew Otten!
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Matthew Otten
Atomic, molecular and optical and quantum theorist Matthew Otten will join the UW–Madison physics department as an assistant professor on January 3, 2024. He joins us most recently from HRL Laboratories. Prior to HRL, Otten earned his PhD from Cornell University, and then was the Maria Goeppert Mayer fellow at Argonne National Laboratory.
Please give an overview of your research.
Very generally, my goal is to make utility scale quantum computing a reality, and to get there faster than we would otherwise without my help. We have a lot of theoretical reasons to believe that quantum algorithms will be faster in certain areas; in practice, we need to know how expensive it’s going to be. It could be that a back of the envelope calculation says a quantum computer might be better, but because quantum computers are very expensive to build and have a lot of overhead, you could find that once you crunch the numbers really carefully, it turns out to cost more money or more energy or more time than just doing it on a supercomputer. In that case, it’s not worth the investment to build it, or at least not at this point. Part of my research is to understand and develop quantum algorithms and count how expensive they are. Once you do that, you can figure out the reason it’s so expensive is A and B. Then we go and we try to fix A and B, and then whack-a-mole all these bottlenecks down and eventually you go from, “It’ll never work,” to “Okay, it’ll work in twenty years.”
Another part of my research is looking at the physical qubits. These devices all have a lot of deep physics inside of them. If you just look at it from the quantum algorithm level, you might get so far. But if you dig down and try to understand the underlying physics, I think you can get further. You might be able to make devices cheaper, faster, or more performant in general. I do a lot of simulations of the underlying physics of these various types of qubits to understand what their properties are, what causes the noise that ruins computation, and what we can do to fix that noise. Through simulations on classical computers, sometimes very large ones, we come up with ways to tweak the system so that you get better performance, by coming up with better quantum algorithms and better qubits. Put those together and hopefully you get to a better quantum computer.
Once you arrive in Madison, what are one or two research projects you think your group will focus on first?
I’ll be bringing a few projects with me. The first is part of a DARPA program called Quantum Benchmarking, which I was part of while at HRL. We found really high-value computational tasks, not specifically quantum, that Boeing, which owns HRL, would like calculated: for instance, reducing corrosion. Corrosion causes planes to be grounded for maintenance, which is costly. Reducing corrosion will reduce maintenance costs and increase uptime. We’ve been developing ways to ask and answer the question, how close are today’s quantum computers to solving that problem? How big do quantum computers need to be to solve that problem? The specific task is understanding what it takes to solve such a large-scale problem, counting the quantum resources that are necessary and coming up with tests so that you could go to a quantum computer, run the tests, and hopefully be able to predict how much bigger or how much faster they would need to be to solve the problem.
Another one comes from the Wellcome Leap Foundation. We are trying to do the largest, most accurate calculation of biological objects — a molecule, string of carbon, something like this — possible on a real-life quantum computer. We’re trying to take techniques that have already been developed or develop new techniques to make circuits smaller, which means a less expensive quantum computer, and faster. That one is a competition, they gave us funding to do it, but if we complete the task better than other competitors, we get more funding to do more.
What attracted you to UW–Madison?
The strength of the science that’s happening in the physics and broader Wisconsin community is very attractive. When I visited, everyone was very nice, it’s a very collegial department. And being from St. Louis, I like the Midwest. I’ve lived in Southern California for a couple of years now and I haven’t seen snow, and that’s sad. Madison is a lovely area. Great people.
What is your favorite element and/or elementary particle?
I think it has to be silicon. Silicon is used in classical computing and potentially has use in quantum computing. And you’re carrying around silicon right now, just like everyone else.
What hobbies and interests do you have?
I have a Siberian Husky puppy and we’ll be very happy to go to Madison and do a lot of skijoring, which is cross country skiing, but the dog pulls you. I started running recently and I was jazzed up for my first half marathon and then I got COVID and I didn’t do it, so I’m still jazzed up for my first half marathon. I play a lot of board games and have a very large board game collection. And my daughter just turned one. She’s become a new hobby.
NASA funds Fundamental Physics proposal from Shimon Kolkowitz
NASA’s Fundamental Physics Program has selected seven proposals, including one from UW–Madison physics professor Shimon Kolkowitz, submitted in response to the Research Opportunities in Space and Earth Sciences – 2022 Fundamental Physics call for proposal.
The selected proposals are from seven institutions in seven states, with the total combined award amount of approximately $9.6 million over a five-year period. Kolkowitz’s proposal is ““Developing new techniques for ultra-high-precision space-based optical lattice clock comparisons.”
Three of the selected projects will involve performing experiments using the Cold Atom Laboratory (CAL) aboard the International Space Station (ISS). Four of the selected proposals call for ground-based research to help NASA identify and develop the foundation for future space-based experiments.
The Fundamental Physics Program is managed by the Biological and Physical Sciences Division in NASA’s Science Mission Directorate. This program performs carefully designed research in space that advances our understanding of physical laws, nature’s organizing principles, and how these laws and principles can be manipulated by scientists and technologies to benefit humanity on Earth and in space.
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