Characterization of tunable coupler without a dedicated readout resonator in superconducting circuits

作者：Chi Zhang, Tian-Le Wang, Liang-Liang Guo, Xiaoyan Yang, Xin-Xin Yang, Peng Duan, Zhi-Long Jia, Weicheng Kong, Guo‐Ping Guo · 发表于：Applied Physics Letters · 年份：2023 · DOI：10.1063/5.0135219 · 被引用次数：9 · 研究领域：Quantum Computing Algorithms and Architecture、Quantum Information and Cryptography、Quantum and electron transport phenomena

Tunable couplers have recently emerged as an essential component in superconducting quantum processors. These couplers usually do not have readout resonators to save control or hardware overhead; this makes it challenging to characterize and calibrate the coupler, which will undoubtedly limit the performance of a fast two-qubit gate. Here, we theoretically demonstrate that by mapping the coupler's state onto that of its neighboring qubit, the high-contrast readout of the coupler can be realized. We experimentally implement such a readout scheme with a single-shot readout fidelity of 86%, which is mainly limited by the thermal population of our sample. We further demonstrate how to calibrate the flux crosstalk related to the coupler and its flux distortion that are ignored in the previous works. These calibration steps are imperative for realizing robust and accurate quantum operations in frequency-tunable superconducting circuits.