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This research introduces a sub-second adaptive spectroscopy technique that captures fast two-level-system dynamics in superconducting qubits, which were previously obscured by slower conventional measurement methods. By leveraging FPGA-based controllers to resolve these rapid fluctuations across multiple devices and laboratories, the study provides critical new data for characterizing defect-induced errors and improving calibration protocols. This advancement directly addresses a fundamental bottleneck limiting coherence times and stability in scalable quantum processors.
Adaptive Spectroscopy of Fast Two-Level-System Dynamics in Superconducting Qubits
arXiv:2608.02086v1 Announce Type: new Abstract: Parasitic two-level-system (TLS) defects are a major source of energy relaxation and temporal instability in superconducting quantum processors. Our sub-second adaptive spectroscopy reveals telegraphic switching of TLSs with a characteristic timescale of a few seconds and spectral diffusion with diffusivity $D \approx 0.9~\mathrm{MHz}^2/\mathrm{s}$. These timescales are about $3 \times 10^2$ times faster than what is observed in conventional nonadaptive spectroscopy, which typically requires hours of measurement time. We resolve such fast dynamics on a field-programmable gate array (FPGA)-based controller that enables measurement of frequency- and time-resolved relaxations with sub-second temporal resolution in flux-tunable superconducting qubits. We observe similar defect dynamics across multiple qubits in independently fabricated devices measured in different laboratories. We correlate TLS-induced fluctuations with gate-level errors using randomized benchmarking. Our results reveal a previously inaccessible regime of frequency-resolved TLS dynamics and redefine the timescales relevant to TLS-aware characterization and calibration of superconducting quantum processors.
Authors:Fabrizio Berritta, David Pahl, Lukas Pahl, William P. Banner, Gabriel Cutter, Jan A. Krzywda, Spencer Weeden, Shravan Patel, Paul Buttles, Stanislav Eilhart, Michael Gingras, Bethany M. Niedzielski, Robert McDermott, Mollie E. Schwartz, Kyle Serniak, Max Hays, Jeffrey A. Grover, William D. Oliver
Abstract:Parasitic two-level-system (TLS) defects are a major source of energy relaxation and temporal instability in superconducting quantum processors. Our sub-second adaptive spectroscopy reveals telegraphic switching of TLSs with a characteristic timescale of a few seconds and spectral diffusion with diffusivity $D \approx 0.9~\mathrm{MHz}^2/\mathrm{s}$. These timescales are about $3 \times 10^2$ times faster than what is observed in conventional nonadaptive spectroscopy, which typically requires hours of measurement time. We resolve such fast dynamics on a field-programmable gate array (FPGA)-based controller that enables measurement of frequency- and time-resolved relaxations with sub-second temporal resolution in flux-tunable superconducting qubits. We observe similar defect dynamics across multiple qubits in independently fabricated devices measured in different laboratories. We correlate TLS-induced fluctuations with gate-level errors using randomized benchmarking. Our results reveal a previously inaccessible regime of frequency-resolved TLS dynamics and redefine the timescales relevant to TLS-aware characterization and calibration of superconducting quantum processors.
Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
arXiv:2608.02086 [quant-ph]
(or arXiv:2608.02086v1 [quant-ph] for this version)
https://doi.org/10.48550/arXiv.2608.02086 arXiv-issued DOI via DataCite (pending registration)
Full text under the publisher's open licence · 211 words
