Probing the Origin of Magnetic Flux Noise using Superconducting Qubits

L. Ateshian | D. A. Rower | L. Li, B. Kannan | K. Serniak | D. Bluvstein | L. Ding, A. Almanakly | J. Braumueller | D. K. Kim | A. Melville | B. M. Niedzielski | J. L. Yoder | M. E. Schwartz | T. P. Orlando | J. Wang | S. Gustavsson | R. Comin | W. D. Oliver

Superconducting qubits are a promising platform for realizing applications in quantum information science and technology. However, a major challenge is mitigating qubit dephasing due to environmental fluctuations, particularly low-frequency magnetic flux noise. Flux noise is commonly attributed to surface defect species such as adsorbed molecular oxygen, but the microscopic origins of these presumed surface spins have not been thoroughly studied. While it is known that certain dephasing errors can be corrected by applying sequences of dynamical decoupling pulses, more is required to further reduce qubit decoherence to levels needed for scaling.

To this end, we focus on a set of spectroscopy protocols to probe the origin of the low-frequency flux noise, including passive (free evolution) and active (driven evolution) techniques, to specifically identify the microscopic surface defect species with the ultimate goal of eliminating them. We present progress on theory and experiments using magnetic fields applied to superconducting qubits to detect parasitically coupled spins. Once the specific noise sources are identified, developing surface treatments or advanced decoupling protocols to further extend qubit lifetimes may bring superconducting quantum computing closer to reality.

Funding Sources: National Science Foundation Graduate Research Fellowship |Department of Energy | Under Secretary of Defense for Research and Engineering