Adaptive Spectroscopy of Fast Two-Level-System Dynamics in Superconducting Qubits

• URL: http://arxiv.org/abs/2608.02086v1
• Date: Mon, 03 Aug 2026 11:44:42 GMT
• Title: Adaptive Spectroscopy of Fast Two-Level-System Dynamics in Superconducting Qubits
• Abstract summary: Parasitic two-level-system (TLS) defects are a major source of energy relaxation and temporal instability in superconducting quantum processors.<n>Our sub-second adaptive spectroscopy reveals telegraphic switching of TLSs with a characteristic timescale of a few seconds.<n>Results reveal a previously inaccessible regime of frequency-induced TLS dynamics and redefine the relevant to TLS-aware characterization and calibration of superconducting quantum processors.
• Score: 0.23977562853295534
• License: http://creativecommons.org/licenses/by/4.0/
• 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.

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