Beating the break-even point with a discrete-variable-encoded logical qubit

Abstract Quantum error correction (QEC) aims to protect logical qubits from noises by using the redundancy of a large Hilbert space, which allows errors to be detected and corrected in real time 1. In most QEC codes 2–8, a logical qubit is encoded in some discrete variables, for example photon numbers, so that the encoded quantum information can be unambiguously extracted after processing. Over the past decade, repetitive QEC has been demonstrated with various discrete-variable-encoded scenarios 9–17. However, extending the lifetimes of thus-encoded logical qubits beyond the best available physical qubit still remains elusive, which represents a break-even point for judging the practical usefulness of QEC. Here we demonstrate a QEC procedure in a circuit quantum electrodynamics architecture 18, where the logical qubit is binomially encoded in photon-number states of a microwave cavity 8, dispersively coupled to an auxiliary superconducting qubit. By applying a pulse featuring a tailored frequency comb to the auxiliary qubit, we can repetitively extract the error syndrome with high fidelity and perform error correction with feedback control accordingly, thereby exceeding the break-even point by about 16% lifetime enhancement. Our work illustrates the potential of hardware-efficient discrete-variable encodings for fault-tolerant quantum computation 19.

Authors

Zhongchu Ni; Sai Li; Xiaowei Deng; Yanyan Cai; Libo Zhang; Weiting Wang; Zhen‐Biao Yang; Haifeng Yu; Fei Yan; Song Liu; Chang‐Ling Zou; Luyan Sun; Shi‐Biao Zheng; Yuan Xu; Dapeng Yu

Published

Mar 22, 2023

Journal or venue

Nature

DOI

10.1038/s41586-023-05784-4

Paper type

journal article

Source

Openalex