Chicago Quantum Profile: Roman Kuzmin

Editor’s note: This is part of a series of profiles of scientists and engineers from across the Chicago Quantum Exchange member institutions.

After finishing his PhD in condensed matter physics, Roman Kuzmin wanted to “find something exciting” for the next stage of his career. Quantum information technology sparked his interest, so he took a position at the Joint Quantum Institute at the University of Maryland researching superconducting qubits. But condensed matter—a broad field that focuses on the study of materials—remained essential to his work.

As Kuzmin built his career, becoming the Dunson Cheng Assistant Professor of Physics at the University of Wisconsin–Madison earlier this year, he found a home at the intersection of the two fields, leveraging his expertise in each to better study the other.

“I essentially have two backgrounds: condensed matter physics and quantum information science,” he said. “I use quantum information to solve condensed matter problems, and I use condensed matter knowledge to improve qubits.”

Condensed matter physics focuses on the properties of materials and the microscopic processes that create those properties. Quantum information is a more specialized area, one that focuses on creating and manipulating information using the quantum states of a system. Kuzmin is drawing on both as he prepares to launch experimental research in quantum simulations and superconducting qubits in his new lab at UW–Madison. It is work that could contribute to a variety of advancements, including in quantum computing.

Quantum simulations use one kind of quantum system to model the behavior and properties of a different quantum system that is difficult to study directly. For example, a large superconducting circuit with qubits—like the ones Kuzmin works with—can be used to model the behavior of electrons in a material or the behavior of decaying particles. In this way, Kuzmin uses his quantum information research to answer questions in other fields, including condensed matter physics.

“You design the circuit in a way that it behaves like something else,” he said. “You are trying to solve a problem in another field that is hard to solve or hard to do an experiment for. You have much more control, and it is much easier to get information from superconducting circuits.”

The superconducting qubits he works with are called fluxonium qubits. Unlike the more ubiquitous transmon qubits—which are used by Google and IBM, for example—these include a component called a superinductor. This difference has allowed Kuzmin and his colleagues to demonstrate longer coherence times with fluxonium qubits—a potentially important finding because the longer a quantum system coheres, the longer it can hold information. This is essential to the development of quantum computers and has been an important focus for quantum scientists.

“I’m excited about the growing complexity of superconducting circuits,” Kuzmin said. “Because I think that’s the way to go, with quantum simulations. You get into the most interesting physics, at least for me right now, which is physics that involves many degrees of freedom, many particles, and many strong interactions between them.”

Just as his quantum simulation technology helps model condensed matter systems, he says his knowledge of condensed matter experimental techniques helps him design better fluxonium qubits, though they still need more improvements in order to be implemented in a quantum computer.

“It’s a good time” to join quantum, he said. “There is still a lot of work to do.”

In his spare time, Kuzmin likes reading, traveling, and juggling—up to five balls, rings, or clubs at a time, alone or in a group. He attended juggling school in St. Petersburg, Russia, before he moved to Maryland, and is planning to teach his students how to juggle as a group activity while they continue to set up their lab. He says he hopes to start experiments in the next month or so.

“I like Madison very much, I’m really enjoying being here,” Kuzmin said. “It’s very nice, I like being close to the lakes, and it’s very compact so I don’t need to spend a lot of time driving. There’s just a wonderful quality of life here.”