A joint research team from Southern University of Science and Technology of China, Tsinghua University, Fuzhou University, University of Science and Technology of China, and Beijing Academy of Quantum Information Sciences demonstrates a breakthrough QEC experiment, where the break-even point for a discrete-variable qubit is beaten by repetitive error detections and corrections in real time. This work is recently published online in Nature (s41586-023-05784-4) titled “Beating the break-even point with a discrete-variable-encoded logical qubit”.
In the past few decades, tremendous progress in superconducting quantum computing has been made: both coherence times and the number of qubits integrated on a chip have been significantly improved, and quantum advantage has been realized experimentally. However, the demonstration of large-scale superconducting quantum circuits is still facing the major obstacle of decoherence. Quantum error correction (QEC), believed to be able to fight against decoherence, is thus vital for realizing universal and reliable quantum computers.
As a significant milestone, demonstrating the QEC advantage of extending the lifetime of the protected quantum information over the best available physical component, i.e., beyond the break-even point, is extremely desirable. To achieve this goal, a logical qubit is binomially-encoded in photon-number states of a microwave cavity and dispersively coupled to an ancilla superconducting qubit. Such a logical qubit can correct single photon losses, the dominant error channel of this system. This QEC scheme benefits from the infinite dimensional Hilbert space of the cavity for redundant information encoding without increasing the number of error channels, thus greatly reduces the hardware requirement. By using fast real-time feedback control technique, the joint team demonstrates the exceeding of the break-even point of QEC by about 16%, representing a key step towards scalable quantum computing.
Fig.1 The quantum error correction protocol.
Fig.2 Quantum error correction results show the beating of break-even point.
Publication link：https://www.nature.com/articles/s41586-023-05784-4
