Implementing arbitrary single-qubit gates with near perfect fidelity is among the most fundamental requirements in gate-based quantum information processing. In this work, we fabric a transmon qubit with long coherence times and demonstrate single-qubit gates with the average gate error below 10−4, i.e. (7.42±0.04)×10−5 by randomized benchmarking (RB). To understand the error sources, we experimentally obtain an error budget, consisting of the decoherence errors lower bounded by (4.62±0.04)×10−5 and the leakage rate per gate of (1.16±0.04)×10−5. Moreover, we reconstruct the process matrices for the single-qubit gates by the gate set tomography (GST), with which we simulate RB sequences and obtain single-qubit fedlities consistent with experimental results. We also observe non-Markovian behavior in the experiment of long-sequence GST, which may provide guidance for further calibration. The demonstration extends the upper limit that the average fidelity of single-qubit gates can reach in a transmon-qubit system, and thus can be an essential step towards practical and reliable quantum computation in the near future.
@article{arxiv.2302.08690,
title = {Error per single-qubit gate below $10^{-4}$ in a superconducting qubit},
author = {Zhiyuan Li and Pei Liu and Peng Zhao and Zhenyu Mi and Huikai Xu and Xuehui Liang and Tang Su and Weijie Sun and Guangming Xue and Jing-Ning Zhang and Weiyang Liu and Yirong Jin and Haifeng Yu},
journal= {arXiv preprint arXiv:2302.08690},
year = {2023}
}