Recently, under the leadership of Prof. Dapeng Yu, a joint research team consisting of Dr. Yuan Xu from Shenzhen International Quantum Research Institute (One of the top ten fundamental research institutes of Southern University of Science and Technology), Professor Shibiao Zheng from Fuzhou University and Professor Luyan Sun from Tsinghua University, made breakthroughs in the field of quantum error correction based on superconducting quantum circuit systems after overcoming various difficulties. The joint team prolonged the storage time of quantum information through real-time repeated quantum error correction technology, surpassing the break-even point for the first time internationally and demonstrating the advantage of quantum error correction. This milestone breakthrough represents a key step towards practical and scalable universal quantum computation, and the related research results have just been published online in Nature titled "Beating the break-even point with a discrete-variable-encoded logical qubit."

Although the research in the field of quantum information processing based on superconducting quantum circuit systems has developed rapidly in recent years, quantum error correction is still indispensable to building a universal quantum computer with practical value because the error rate of the quantum computer system is much higher than that of classical computers. Quantum error correction can effectively protect quantum information from interference by environmental noise. To encode a logical quantum qubit, traditional quantum error correction schemes require multiple redundant physical qubits, which results in huge hardware resource cost, and the number of error-prone channels also increases significantly with the number of qubits, leading to a potentially embarrassing situation of "more correction, more error."

Figure 1. Schematic diagram of the quantum error correction process.

To overcome the above difficulties, the joint team utilized the infinite-dimensional Hilbert space in microwave harmonic oscillators or Bosonic mode system to realize redundant coding and quantum error correction of quantum information. The quantum error correction approach based on Bosonic coding possesses the advantage of simple error types, convenient error detection, good coherence performance, more efficient hardware, and simple feedback control in the superconducting quantum circuit system. In this work, the research team developed a high-coherence quantum system, designed to realize a low-error-rate error symptom detection method, and optimized the quantum error correction technology, ultimately achieving a logical qubit based on discrete-variable-encoded binomial coding in the Bosonic mode. The storage time of quantum information was prolonged using real-time repeated quantum error correction, and the results exceeded the best value without error correction for the first time, beyond the break-even point. This is also the first time that the storage time of quantum information has been prolonged beyond the break-even point through active repeated error detection and correction, which shows significant milestone significance. 

Figure 2. Experimental characterization results of quantum error correction operations.

In this work, Zhongchu Ni, a doctoral candidate at Southern University of Science and Technology, is the first author of this paper. Dr. Yuan Xu is the main corresponding author. Professor Luyan Sun, Professor Shibiao Zheng, and Prof. Dapeng Yu are the joint corresponding authors.

论文链接：

https://www.nature.com/articles/s41586-023-05784-4