超导量子比特中快速二能级系统动力学的自适应光谱学研究
Adaptive Spectroscopy of Fast Two-Level-System Dynamics in Superconducting Qubits
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中文总结 AI 辅助
针对超导量子比特中寄生TLS缺陷引发的稳定性问题，提出基于FPGA的亚秒级自适应光谱方法，观测到比传统方法快约300倍的TLS快速动力学，并关联其与门级误差，重新定义了相关表征校准的时间尺度。
中文摘要 AI 辅助
寄生二能级系统（TLS）缺陷是超导量子处理器中能量弛豫和时间不稳定性的主要来源。我们的亚秒级自适应光谱学揭示了TLS的电报式开关（特征时间尺度为几秒）以及扩散系数约为$D \approx 0.9~\mathrm{MHz}^2/\mathrm{s}$的光谱扩散。这些时间尺度比传统非自适应光谱学（通常需要数小时测量时间）观测到的快约$3 \times 10^2$倍。我们通过基于现场可编程门阵列（FPGA）的控制器解析了这类快速动力学，该控制器可在通量可调超导量子比特中以亚秒时间分辨率测量频率分辨和时间分辨的弛豫过程。我们在不同实验室测量的、独立制备的器件中的多个量子比特上观测到了相似的缺陷动力学。我们使用随机基准测试将TLS诱导的涨落与门级误差关联起来。我们的结果揭示了此前无法触及的频率分辨TLS动力学区间，并重新定义了与超导量子处理器的TLS感知表征和校准相关的时间尺度。
英文摘要
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.
