Research, teaching and outreach in Physics at UW–Madison
Correlated errors in quantum computers emphasize need for design changes
Quantum computers could outperform classical computers at many tasks, but only if the errors that are an inevitable part of computational tasks are isolated rather than widespread events.
Now, researchers at the University of Wisconsin–Madison have found evidence that errors are correlated across an entire superconducting quantum computing chip — highlighting a problem that must be acknowledged and addressed in the quest for fault-tolerant quantum computers.
The researchers report their findings in a study published June 16 in the journal Nature, Importantly, their work also points to mitigation strategies.
“I think people have been approaching the problem of error correction in an overly optimistic way, blindly making the assumption that errors are not correlated,” says UW–Madison physics Professor Robert McDermott, senior author of the study. “Our experiments show absolutely that errors are correlated, but as we identify problems and develop a deep physical understanding, we’re going to find ways to work around them.”
The UW–Madison Physics Department is pleased to welcome 18 students to the M.S. in Physics – Quantum Computing program. These students make up the third cohort to begin the program and are the largest entering class to date.
“We are really pleased and proud that the MSPQC program continues to grow and prosper in its third year,” says Bob Joynt, MSPQC Program Director and professor of physics. “We look forward to providing a great experience for the class of 2021. A particular focus this year will be the formation of collaborative teams that will push forward research in quantum computing.”
Of note, three women are in the entering class, marking the first time that women have enrolled in MSPQC. Other facts and figures about this year’s cohort include:
11 students are coming directly from completing their Bachelors
Three students have Master’s degrees
Six students have at least four years of professional experience, and four of those students have over 10 years professional experience
15 are international students, and seven of those students have attended U.S. institutions for previous studies
The students’ academic backgrounds include physics, astronomy, engineering, and business administration.
The department is following University guidelines and is planning for students to join us in Madison this fall, with in-person instruction. Over the summer, students can attend optional virtual orientation sessions to prepare for the program.
“The pandemic imposed restrictions on our admissions and recruitment activities which forced us to work virtually, but I believe these barriers made our programming more accessible and led to the most diverse and determined incoming cohort of MSPQC students to date,” says Jackson Kennedy, MSPQC coordinator. “Although I have been able to meet our incredibly talented students virtually, I cannot wait to greet them in-person this Fall as we celebrate a long-awaited return to campus.”
In addition to Joynt, the department thanks the other faculty who serve on the MSPQC admissions committee — Alex Levchenko, Robert McDermott, Maxim Vavilov and Deniz Yavuz — for application review. We also thank Michelle Holland and Jackson Kennedy for organizing recruiting efforts.
The MSPQC program welcomed its first students in Fall 2019 – the first-ever class of students in the U.S. to enroll in a quantum computing M.S. degree program. The accelerated program was born out of a recognized need to rapidly train students for the quantum computing workforce and is designed to be completed in 12 months. It provides students with a thorough grounding in the new discipline of quantum information and quantum computing.
Congratulations to Professor Sue Coppersmith on her retirement!
With the best of wishes — and some sadness — the Department of Physics says “Happy Retirement” to Professor Sue Coppersmith. Her last day at UW–Madison was February 14.
Coppersmith, the Robert E. Fassnacht Professor of Physics, joined the department in 2001. Prior to coming to UW–Madison, she earned her Ph.D. from Cornell University, conducting her thesis work at Bell Labs. She completed a postdoc at Brookhaven National Lab, then worked at Bell Labs for eight years before joining the faculty at the University of Chicago.
During her tenure here, she served as Department Chair for one three-year term, and earned recognition as a Fellow of the National Academy of Sciences, the American Academy of Arts and Sciences, the American Association for the Advancement of Science, and the American Physical Society.
At UChicago, Coppersmith’s research focused on soft matter physics and non-linear dynamics, work that she continued at UW–Madison, primarily with Prof. Pupa Gilbert. But her research program largely shifted over the years into quantum computing, an area that was just getting started when she started in Madison..
“At the time, I would tell people what we were doing, and of course nothing was working yet, and people would say, ‘Well, that’s all crap, isn’t it?’” Coppersmith recalls. “So, it was really fun to go from a time where there was nothing working, to now we have qubits, and being a part of the effort and feeling like I was helping.”
Coppersmith describes herself as a theorist who went into the lab every day to better understand the experimental side of quantum computing, And, she says, UW–Madison stands out as one of the universities where theory and experiment are so closely tied together. Here, she frequently collaborated with Prof. Mark Eriksson and Distinguished Scientist Mark Friesen.
“She just comes up with a lot of ideas, and what matters most is how many of them are home runs. She had an unusually large number,” Eriksson says. “She came up with the idea for a brand new qubit, the quantum dot hybrid qubit, and we’re still working on it to this day in my lab. And other people around the world have picked it up.”
“As a researcher, Sue is highly intuitive and focused more on the high-level physical picture rather than specific technical details. She typically breaks a problem down to a ‘minimal model’ that captures its basic physics. She has studied a wide variety of problems in her career, for which she is highly respected in many different communities, and she is able to apply lessons learned from one area to another. Her memory is legendary! She is also known for her quickness, both in being able to understand a problem (and how it fits into the big picture) and being able to immediately respond to it. I also say this in a good way: she is not shy about expressing her opinions.”
Legacy as Department Chair
Perhaps equal to her scientific achievements is the mark Coppersmith made on the department during her time as Chair, from 2005-08. The Department was hiring three faculty positions, and she reasoned that if eight offers were made, at worst four people would accept.
“But eight people came! And I was famous for it because I ruined the College’s budget,” Coppersmith says. “I think this is the highlight of my Chair career. I loved recruiting people.”
There are a number of factors that go into faculty candidates accepting or not accepting offers, but Eriksson is certain that Coppersmith‘s ability to recruit was a significant one.
“They came in large part because Sue understood and was able to get them to explain and she was able to hear what they really needed, and then go deliver on it,” Eriksson says. “It’s one thing to have any subset of those skills, but she has the whole package.”
Current Department Chair Sridhara Dasu credits Coppersmith with shaping the direction of the department in all areas of physics, adding, “Her tenure continues to be an inspiration for all chairs of the department who followed her.”
Mentorship of students and colleagues
Coppersmith’s mentorship of junior colleagues and students will also be missed. Both Friesen and Susan Nossal, senior scientist and director of the Physics Learning Center, noted that Coppersmith’s support has been crucial to their success as researchers in the department. They both applauded her as a champion of women and girls in science, citing her participation – with Nossal, Gilbert and several graduate students – in the annual Expanding Your Horizons event at which middle school girls participate in fun, hands-on science activities.
“As a mentor, she is highly dedicated to her students and colleagues,” says Friesen, who co-advised several students with Coppersmith. “For me personally, she has been very supportive of my career path, helping me to obtain promotions and advancements, and providing on-point advice.”
Adds Nossal: “As a scientist, you have your ups and downs, and she helped me through some of the downs. It’s always helpful to have people who believe in you, and she helped me in persisting as a scientist.”
Between Coppersmith and everyone else mentioned in this piece, there were certainly plenty of stories that could be shared. But for now, we’ll let emeritus professor Lou Bruch sum up Coppersmith’s tenacity and well-placed ambition with this anecdote:
“Sue touted the usefulness of the Mathematica package and would at times get into competition on speed of getting to the answer — her using the package and me using ad hoc analyses. I recall only one instance where I won.”
Coppersmith may be retired from UW–Madison, but she is not retiring from science. She is currently Professor and Head of the School of Physics at the University of New South Wales in Australia, where she will continue her research and collaborations with colleagues here and around the world.
“Wisconsin was so good to me. The people are so nice, and we did good work,” Coppersmith says. “I like to feel that I contributed in a positive way. I’ll always be grateful.”
Mark Friesen promoted to Distinguished Scientist
Congratulations to Mark Friesen on his promotion to Distinguished Scientist! The distinguished title is the highest title available to an academic staff member at UW–Madison.
Friesen joined the physics department in 2004 as an associate scientist, and has been with UW–Madison since 1998, when he began a postdoc in the Materials Sciences and Engineering department. His main research effort at UW–Madison has been related to silicon quantum dot quantum computing, in collaboration with physics professors Mark Eriksson, Sue Coppersmith, Bob Joynt, Maxim Vavilov, and others.
Friesen says his most important achievement in the department is serving as a research advisor: In 16 years with UW–Madison physics, he has advised or co-advised six postdocs, 11 Ph.D. theses, four current Ph.D. students, two M.S. theses, and several undergraduate research projects. He also has 123 peer-reviewed publications and five U.S. patents, and serves as a consultant for ColdQuanta, a quantum computing company.
“Mark is known around the world for his expertise in semiconductor-based quantum computing,” Mark Eriksson says. “He is especially well known for his calculations on how the band structure in silicon interacts with interfaces to determine the quantum states for electrons in silicon-based quantum devices.”
Congrats, Mark Friesen, on this well-deserved honor!
Chuanhong (Vincent) Liu named to Fall 2020 cohort of the Quantum Information Science and Engineering Network (QISE-NET)
Graduate student Chuanhong (Vincent) Liu (McDermott Group) has had his project awarded funding through QISE-NET, the Quantum Information Science and Engineering Network. Run through the University of Chicago, QISE-NET is open to any student pursuing an advanced degree in any field of quantum science. Liu and other students in his cohort earn up to three years of support, including funding, mentoring and training at annual workshops. All awardees are paired with a mentoring QISE company or national lab, at which they will complete part of their projects. Liu describes his project, below. Cecilia Vollbrecht, a grad student in Chemistry, also earned this honor. Both Liu and Volbrecht are students in the Wisconsin Quantum Institute.
The Single Flux Quantum (SFQ) digital logic family has been proposed as a scalable approach for the control of next-generation multiqubit arrays. With NIST’s strong track record in the field of SFQ digital logic and the expertise of McDermott’s lab in the superconducting qubit area, we expect to achieve high fidelity SFQ-based qubit control. The successful completion of this research program will represent a major step forward in the development of a scalable quantum-classical interface, a critical component of a fully error-corrected fault-tolerant quantum computer.
Robert McDermott elected Fellow of the American Physical Society
Congratulations to Prof. Robert McDermott, who was elected a 2020 Fellow of the American Physical Society! He was elected for seminal contributions to quantum computing with superconducting qubits, including elucidating the origins of decoherence mechanisms, and development of new qubit control and readout methods. He was nominated by the Division of Quantum Information.
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.
Q-NEXT collaboration awarded National Quantum Initiative funding
The University of Wisconsin–Madison solidified its standing as a leader in the field of quantum information science when the U.S. Department of Energy (DOE) and the White House announced the Q-NEXT collaboration as a funded Quantum Information Science Research Center through the National Quantum Initiative Act. The five-year, $115 million collaboration was one of five Centers announced today.
Q-NEXT, a next-generation quantum science and engineering collaboration led by the DOE’s Argonne National Laboratory, brings together nearly 100 world-class researchers from three national laboratories, 10 universities including UW–Madison, and 10 leading U.S. technology companies to develop the science and technology to control and distribute quantum information.
“The main goals for Q-NEXT are first to deliver quantum interconnects — to find ways to quantum mechanically connect distant objects,” says Mark Eriksson, the John Bardeen Professor of Physics at UW–Madison and a Q-NEXT thrust lead. “And next, to establish a national resource to both develop and provide pristine materials for quantum science and technology.”
Q-NEXT will focus on three core quantum technologies:
Communication for the transmission of quantum information across long distances using quantum repeaters, enabling the establishment of “unhackable” networks for information transfer
Sensors that achieve unprecedented sensitivities with transformational applications in physics, materials, and life sciences
Processing and utilizing “test beds” both for quantum simulators and future full-stack universal quantum computers with applications in quantum simulations, cryptanalysis, and logistics optimization.
Eriksson is leading the Materials and Integration thrust, one of six Q-NEXT focus areas that features researchers from across the collaboration. This thrust aims to: develop high-coherence materials, including for silicon and superconducting qubits, which is an essential component of preserving entanglement; develop a silicon-based optical quantum memory, which is important in developing a quantum repeater; and improve color-center quantum bits, which are used in both communication and sensing.
“One of the key goals in Materials and Integration is to not just improve the materials but also to improve how you integrate those materials together so that in the end, quantum devices maintain coherence and preserve entanglement,” Eriksson says. “The integration part of the name is really important. You may have a material that on its own is really good at preserving coherence, yet you only make something useful when you integrate materials together.”
“I’m excited about Q-NEXT because of the connections and collaborations it provides to national labs, other universities, and industry partners,” Eriksson says. “When you’re talking about research, it’s those connections that often lead to the breakthroughs.
The potential impacts of Q-NEXT research include the creation of a first-ever National Quantum Devices Database that will promote the development and fabrication of next generation quantum devices as well as the development of the components and systems that enable quantum communications across distances ranging from microns to kilometers.
“This funding helps ensure that the Q-NEXT collaboration will lead the way in future developments in quantum science and engineering,” says Steve Ackerman, UW–Madison vice chancellor for research and graduate education. “Q-NEXT is the epitome of the Wisconsin Idea as we work together to transfer new quantum technologies to the marketplace and support U.S. economic competitiveness in this growing field.”
New study expands types of physics, engineering problems that can be solved by quantum computers
A well-known quantum algorithm that is useful in studying and solving problems in quantum physics can be applied to problems in classical physics, according to a new study in the journal Physical Review A from University of Wisconsin–Madison assistant professor of physics Jeff Parker.
Quantum algorithms – a set of calculations that are run on a quantum computer as opposed to a classical computer – used for solving problems in physics have mainly focused on questions in quantum physics. The new applications include a range of problems common to physics and engineering, and expands on the types of questions that can be asked in those fields.
“The reason we like quantum computers is that we think there are quantum algorithms that can solve certain kinds of problems very efficiently in ways that classical computers cannot,” Parker says. “This paper presents a new idea for a type of problem that has not been addressed directly in the literature before, but it can be solved efficiently using these same quantum computer types of algorithms.”
The type of problem Parker was investigating is known as generalized eigenvalue problems, which broadly describe trying to find the fundamental frequencies or modes of a system. Solving them is crucial to understanding common physics and engineering questions, such as the stability of a bridge’s design or, more in line with Parker’s research interests, the stability and efficiency of nuclear fusion reactors.
As the system being studied becomes more and more complex — more components moving throughout three-dimensional space — so does the numerical matrix that describes the problem. A simple eigenvalue problem can be solved with a pencil and paper, but researchers have developed computer algorithms to tackle increasingly complex ones. With the supercomputers available today, more and more difficult physics problems are finding solutions.
“If you want to solve a three-dimensional problem, it can be very complex, with a very complicated geometry,” Parker says. “You can do a lot on today’s supercomputers, but there tends to be a limit. Quantum algorithms may be able to break that limit.”
The specific quantum algorithm that Parker studied in this paper, known as quantum phase estimation, had been previously applied to so-called standard eigenvalue problems. However, no one had shown that they could be applied to the generalized eigenvalue problems that are also common in physics. Generalized eigenvalue problems introduce a second matrix that ups the mathematical complexity.
Parker took the quantum algorithm and extended it to generalized eigenvalue problems. He then looked to see what types of matrices could be used in this problem. If the matrix is sparse — meaning, if most of the numerical components that make it up are zero — it means this problem could be solved efficiently on a quantum computer.
“What I showed is that there are certain types of generalized eigenvalue problems that do lead to a sparse matrix and therefore could be efficiently solved on a quantum computer,” Parker says. “This type includes the very natural problems that often occur in physics and engineering, so this study provides motivation for applying these quantum algorithms more to generalized eigenvalue problems, because it hasn’t been a big focus so far.”
Parker emphasizes that quantum computers are in their infancy, and these classical physics problems are still best approached through classical computer algorithms.
“This study provides a step in showing that the application of a quantum algorithm to classical physics problems can be useful in the future, and the main advance here is it shows very clearly another type of problem to which quantum algorithms can be applied,” Parker says.
The study was completed in collaboration with Ilon Joseph at Lawrence Livermore National Laboratory. Funding support was provided by the U.S. Department of Energy to Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 and U.S. DOE Office of Fusion Energy Sciences “Quantum Leap for Fusion Energy Sciences” (FWP SCW1680).
UW–Madison named member of new $25 million Midwest quantum science institute
As joint members of a Midwest quantum science collaboration, the University of Wisconsin–Madison, the University of Illinois at Urbana–Champaign and the University of Chicago have been named partners in a National Science Foundation Quantum Leap Challenge Institute, NSF announced Tuesday.
The five-year, $25 million NSF Quantum Leap Challenge Institute for Hybrid Quantum Architectures and Networks (HQAN) was one of three in this first round of NSF Quantum Leap funding and helps establish the region as a major hub of quantum science. HQAN’s principal investigator, Brian DeMarco, is a professor of physics at UIUC. UW–Madison professor of physics Mark Saffman and University of Chicago engineering professor Hannes Bernien are co-principal investigators.
“HQAN is very much a regional institute that will allow us to accelerate in directions in which we’ve already been headed and to start new collaborative projects between departments at UW–Madison as well as between us, the University of Illinois, and the University of Chicago.” says Saffman, who is also director of the Wisconsin Quantum Institute. “These flagship institutes are being established as part of the National Quantum Initiative Act that was funded by Congress, and it is a recognition of the strength of quantum information research at UW–Madison that we are among the first.”
Chicago Quantum Exchange, including UW–Madison, welcomes seven new partners in tech, computing and finance, to advance research and training
The Chicago Quantum Exchange, a growing intellectual hub for the research and development of quantum technology, has added to its community seven new corporate partners in computing, technology and finance that are working to bring about and primed to take advantage of the coming quantum revolution.
These new industry partners are Intel, JPMorgan Chase, Microsoft, Quantum Design, Qubitekk, Rigetti Computing, and Zurich Instruments.
The Chicago Quantum Exchange and its corporate partners advance the science and engineering necessary to build and scale quantum technologies and develop practical applications. The results of their work – precision data from quantum sensors, advanced quantum computers and their algorithms, and securely transmitted information – will transform today’s leading industries. The addition of these partners brings a total of 13 companies into the Chicago Quantum Exchange to work with scientists and engineers at universities and the national laboratories in the region.
“These new corporate partners join a robust collaboration of private and public universities, national laboratories, companies, and non-profit organizations. Together, their efforts — with federal and state support —will enhance the nation’s leading center for quantum information and engineering here in Chicago,” said University of Chicago Provost Ka Yee C. Lee.
“Developing a new technology at nature’s smallest scales requires strong partnerships with complementary expertise and significant resources. The Chicago Quantum Exchange enables us to engage leading experts, facilities and industries from around the world to advance quantum science and engineering,” said David Awschalom, the Liew Family Professor in Molecular Engineering at the University of Chicago, senior scientist at Argonne, and director of the Chicago Quantum Exchange. “Our collaborations with these companies will be crucial to speed discovery, develop quantum applications and prepare a skilled quantum workforce.”
Chicago Quantum Exchange member institutions engage with corporate partners in collaborative research efforts, joint workshops to develop new research directions, and opportunities to train future quantum engineers. The CQE has existing partnerships with Boeing, IBM, Applied Materials, Inc., Cold Quanta, HRL Laboratories, LLC, and Quantum Opus, LLC.
The CQE’s newest corporate partners include a broader set of companies ranging in interest and expertise from quantum communication hardware to quantum computing systems and controls to finance and cryptography applications.
Intel is advancing a systems-level approach to quantum research that demonstrates quantum practicality and a path to commercially viable quantum computing systems. Its research efforts – in partnership with QuTech, the quantum institute of TU Delft and TNO—include technology advancements in silicon spin qubits, control and interconnect systems for large-scale quantum systems, and quantum algorithms.
JPMorgan Chase is a leader in the field of quantum algorithms and applications for financial use cases, such as portfolio optimization, option pricing and reinforcement learning, as well as general foundational algorithms with cross-domain applicability, such as quantum search. The firm has made a significant investment in quantum computing, collaborating with multiple quantum providers and forums. Its research team is also actively working in the area of post-quantum cryptography.
Microsoft has driven advances in scalable quantum technology for nearly two decades. Their global team of physicists, computer and materials scientists, engineers, developers, and enthusiasts are collaborating with a broad community to advance a full-stack quantum computing system, develop practical solutions, enable a quantum community, and accelerate quantum workforce development.
Quantum Design manufactures automated characterization systems that allow research and exploration of new materials & devices. With the partnership, Quantum Design will support research and advanced teaching at the CQE, launching a new student laboratory for quantum measurements and the study of quantum materials.
Qubitekk develops and manufactures a variety of key components for quantum networks. Qubitekk provides entangled photon sources in its support for researchers across the CQE working on the Argonne quantum loop.
Rigetti Computing builds and delivers integrated quantum systems and offers a distinctive hybrid cloud computing access model for practical near-term applications. The company owns and operates Fab-1, the world’s first dedicated quantum integrated circuit foundry.
Zurich Instruments develops advanced instrumentation including quantum control systems that enable reliable control and measurement of superconducting qubits and silicon spin qubits. The company will collaborate with the CQE on student opportunities and research.
Many of the new industry partners already have ongoing or recent engagements with CQE and its member institutions. In recent collaborative research, spectrally entangled photons from a Qubitekk entangled photon source were transported and successfully detected after traveling through one section of the Argonne quantum loop.
Another example of these relationships is the work that University of Chicago computer scientist Fred Chong and his students have done with both Intel and Rigetti Computing on software and hardware solutions. With Intel’s support, Chong’s team invented a range of software techniques to more efficiently execute quantum programs on a coming crop of quantum hardware. For example, they developed methods that take advantage of the hierarchical structure of important quantum circuits that are critical to the future of reliable quantum computation.
Jim Clarke, director of quantum hardware at Intel, looks forward to further collaborations with Chicago Quantum Exchange members.
“Intel remains committed to solving intractable challenges that lie on the path of achieving quantum practicality,” said Clarke. “We’re focusing our research on new qubit technologies and addressing key bottlenecks in their control and connectivity as quantum systems get larger. Our collaborations with members of the Chicago Quantum Exchange will help us harness our collective areas of expertise to contribute to meaningful advances in these areas.”
The Chicago Quantum Exchange’s partnership with JPMorgan Chase will enable the use of quantum computing algorithms and software for secure transactions and high-speed trading.
“We are excited about the transformative impact that quantum computing can have on our industry,” said Marco Pistoia, managing director, head of applied research and engineering at JPMorgan Chase. “Collaborating with the Chicago Quantum Exchange will help us to be among the first to develop cutting-edge quantum algorithms for financial use cases, and experiment with the power of quantum computers on relevant problems, such as portfolio optimization and option pricing.”
Applying quantum science and technology discoveries to areas such as finance, computing and healthcare requires a robust workforce of scientists and engineers. The Chicago Quantum Exchange integrates universities, national laboratories and leading companies to train the next generation of scientists and engineers and to equip those already in the workforce to transition to quantum careers.
“Microsoft is excited to partner with the Chicago Quantum Exchange to accelerate the advancement of quantum computing,” said Chetan Nayak, general manager of Microsoft Quantum Hardware. “It is through these academic and industry partnerships that we’ll be able to scale innovation and develop a workforce ready to harness the incredible impact of this technology.”