Physicist fellow helps shed light on mysteries in quantum computing Meet David Harrison

David Harrison credits his high school physics teacher for his early fascination with science. Not only did he teach Harrision about the properties of physics, but also about how physics is a gateway into understanding the world around us. By becoming a science, technology, engineering and mathematics (STEM) student Harrison was able to begin taking the world apart and contribute to its understanding. He graduated from St. John’s University with his bachelor’s in physics, numerical computation and Spanish. Then, he received his doctoral degree in physics from the University of Minnesota.

“I think that scientific literacy is important for a society as a whole. For our nation to function, we need well-informed citizens who can understand complex, messy data,” said Harrison. “It is important to me that I contribute to ensuring that is the case, and hopefully also spread my love of science in the same way that my high school physics teacher did.”

He first heard about the Intelligence Community Postdoctoral Research Fellowship Program (IC Postdoc) from an alumnus of the program who recommended it. Harrison joined the Office of the Director of National Intelligence (ODNI) as a fellow alongside his mentor Robert McDermott. The IC Postdoc Program offers scientists and engineers from a wide variety of disciplines unique opportunities to conduct research relevant to the Intelligence Community.

Harrison researched alongside McDermott’s team at the University of Wisconsin-Madison with a focus on quantum computing, specifically superconducting qubits. Qubits, or quantum bits, are the most basic unit of information within a quantum system, similar to the bits comprising the binary code of modern computers. They are also sometimes referred to as “artificial atoms,” says Harrison. Superconducting qubits are electrical circuits that conduct electricity without losing energy when cooled. Their electrons pair up into “Cooper pairs,” and when the electrons break apart the broken pairs are detrimental to the quantum system.

“Normally we would expect only around one Cooper pair per 10⁵⁰ to be broken,” explained Harrison. “However, experimentally, it is always observed that one Cooper pair per 10¹⁰, or even more, are broken. This is an enormous discrepancy and a longstanding mystery. Our study shines some light on this problem, and it motivates several avenues for potential improvement.”

Harrison and McDermott’s team used photons to study the properties of superconductors and found that the physical shapes and sizes of qubits resulted in an unexpectedly large number of broken Cooper pairs when photons are sent in at certain frequencies. They were able to detect whenever a pair was broken and brainstormed ways to mitigate it. They currently are developing intricate ways to prevent the unwanted frequencies from reaching their devices.

“In addition, we noted that the origin of this problem for quantum computation is that the qubit structure is too sensitive to its environment,” continued Harrison. “The upshot of this is that these qubits can be efficient quantum sensors.”

Overall, he hopes that his research into broken Cooper pairs will lead to better, more efficient quantum computers. Then, Harrison believes that quantum computing will transform the way we can simulate and understand physics, chemistry and medicine among other scientific fields.

During his fellowship, he assisted with a paper that is being peer-reviewed, called “Quasiparticle Poisoning of Superconducting Qubits from Resonant Absorption of Pair-breaking Photons.” He also presented the research at the American Physical Society in March 2022 and the Quantum Computing Program Review.

As a fellow, Harrison spent his time designing or simulating new devices, fabricating tiny designs in the nanofabrication center and sometimes repairing broken equipment. Harrison tests and prepares new instruments for the lab when they arrive. He also frequently collaborates with other scientists in the lab. He “wholeheartedly recommends this program to others.”

“It is fun to learn new things every day, and exciting to be a part of such a rapidly growing and advancing field,” said Harrison. “The fellowship has definitely increased my opportunities to attend conferences and meet and interact with others in the field.”

The Intelligence Community Postdoctoral Research Fellowship Program is funded by the Office of the Director of National Intelligence (ODNI) and managed by the Oak Ridge Institute for Science and Education (ORISE) under an agreement between the IC and the U.S. Department of Energy (DOE). ORISE is managed for DOE by ORAU.