发表机构
Amazon Center for Quantum Computing; Institute for Quantum Information and Matter, California Institute of Technology; Thomas J. Watson, Sr., Laboratory of Applied Physics, California Institute of Technology（亚马逊量子计算中心; 加州理工学院量子信息与物质研究所; 加州理工学院托马斯·J·沃森Sr.应用物理实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对超导量子电路中TLS损耗问题，本文提出一种仅在态制备和读出阶段使用快速磁通脉冲的序列，实现了0.1 MHz低交换速率下的拉比Chevron图样探测，揭示了此前被认为非相干的TLS的相干特性，其交换相干时间受缀饰能隙保护。
AI 中文摘要
超导量子电路中一项突出的挑战是抑制两能级系统（TLS）缺陷带来的损耗。利用磁通可调量子比特的SWAP谱学可探测单个TLS，但仅在耦合最强的缺陷中观测到了标志相干交换的拉比 Chevron 图样。本文提出一种序列，仅在态制备和读出阶段使用快速磁通脉冲，在能量弛豫延迟阶段关闭脉冲，以获得更精细的频率分辨率和更长的相互作用时间。我们在低至0.1 MHz的交换速率下探测到了拉比 Chevron 图样，比此前报道的结果低一个数量级。在缀饰态图像中，我们拟合相干交换振荡以提取TLS的能量弛豫时间。这些拉比 Chevron 图样揭示了相干TLS，其中值能量弛豫时间为10微秒，对应耦合强度此前被认为与非相干TLS相关。交换相干时间超过了受磁通噪声限制的量子比特T2*，表明缀饰能隙可保护它们免受低频1/f噪声的影响。
英文摘要
An outstanding challenge in superconducting quantum circuits is mitigating loss from two-level system (TLS) defects. SWAP spectroscopy with flux-tunable qubits can detect individual TLSs, but the Rabi chevrons that signal coherent exchange have been observed only for the most strongly coupled defects. Here, we introduce a sequence with fast flux pulses only at state preparation and readout, switched off during the energy-relaxation delay for finer frequency resolution and longer interaction times. We detect Rabi chevrons at swap rates as low as 0.1 MHz, an order of magnitude lower than previously reported. In the dressed-state picture, we fit the coherent swap oscillations to extract the TLS energy-relaxation time. These Rabi chevrons reveal coherent TLSs with a median energy-relaxation time of 10 microseconds, at coupling strengths previously associated with incoherent TLSs. The swap coherence times exceed the qubit T2* limited by flux noise, indicating that the dressed gap protects them from low-frequency 1/f noise.
Comments12 pages, 8 figures, 1 table. Includes Supplemental Material
