Experimental Quantum Error Correction below the Surface Code Threshold via All-Microwave Leakage Suppression
Tan He, W. W. Lin, R. N. Wang, Yuan Li, Jiahao Bei, Jianbin Cai, Sirui Cao, Danning Chen, Kefu Chen, Xiawei Chen, Zhe Chen, Zhiyuan Chen, Zihua Chen, Wenhao Chu, Hui Deng, Xun Ding, Zhuzhengqi Ding, Bo Fan, Daojin Fan, Yuanhao Fu, Dongxin Gao, M. Gong, Jiacheng Gui, Cheng Guo, Shaojun Guo, Lianchen Han, Linyin Hong, Yisen Hu, He-Liang Huang, Yong-Heng Huo, C. P. Jiang, Lei Jiang, Tao Jiang, Zuokai Jiang, Honghong Jin, Dayu Li, Dongdong Li, Jiaqi Li, Jinjin Li, Junyan Li, J.F. Li, Na Li, Shaowei Li, Yuhuai Li, Futian Liang, Nanxing Liao, Jin Lin, Ke Liu, Maliang Liu, YanCheng Liu, Haoxin Lou, Yuwei Ma, K. J. Nan, M. Nie, Le Niu, Wenyi Peng, Haoran Qian, Hao Rong, Rong Tao, Huiyan Shen, Qiong Shen, Hong Su, Feifan Su, Chenyin Sun, Lihua Sun, Tianzuo Sun, Yingxiu Sun, Yimeng Tan, Jun Tan, Wenbing Tu, Jiafei Wang, Biao Wang, Chang Wang, Chen Wang, Chu Wang, Jian Wang, Shengtao Wang, Xinzhe Wang, Zuolin Wei, Dachao Wu, Gang Wu, Yulin Wu, Yu Xu, Chun Jason Xue, Kai Yan, Xin Yan, Weifeng Yang, Xinpeng Yang, Yang Yang, Y. Ye, Zhenping Ye, Zhengzhong Yi, Chong Ying, Jiale Yu, Qinjing Yu, Xiangdong Zeng, Chen Zha, Shaoyu Zhan, Haibin Zhang, He Zhang
Abstract
Quantum error correction (QEC) enables practical quantum computing by encoding logical qubits in many physical qubits, which can exponentially suppress the logical error rate with increasing code size provided that the physical error rate is below a critical threshold. However, the leakage of quantum information from the computational subspace presents a critical challenge to the development of scalable QEC, which creates long-lived, correlated errors that spread across space and time. Here, we demonstrate a quantum memory operating below the threshold by implementing an all-microwave leakage suppression architecture on a distance-7 surface code. We achieve a logical error suppression factor of Λ=1.40(6), definitively reversing the above-threshold scaling (Λ<1) caused by unmitigated leakage. This scheme integrates a hardware-efficient leakage reduction unit for data qubits with a fast, unconditional reset for ancilla qubits, suppressing the average leakage population after 40 cycles by a factor of 72 to 6.4(5)×10^{-4}. Our results demonstrate the viability of all-microwave control architectures for suppressing critical errors at scale, paving the way for more advanced quantum error correction implementations.