近日，清华大学的孙麓岩及其研究小组与中国科学技术大学的邹长铃等人合作并取得一项新进展。经过不懈努力，他们通过量子纠错保护逻辑量子比特之间的纠缠。相关研究成果已于2024年3月6日在国际知名学术期刊《自然—物理学》上发表。

本文通过将量子信息编码到空间分离的微波模式中，从实验上实现了具有玻色子量子模块的纠缠逻辑量子比特。通过重复量子纠错保护了纠缠，与未受保护的逻辑量子比特相比，纠缠的相干时间提高了45%。

此外，研究人员通过对每个逻辑量子比特的独立错误检测和后选择，证明了纯化的纠缠逻辑量子比特违反贝尔不等式，从而导致测量的贝尔信号超过经典界限。受保护的纠缠逻辑量子比特可以应用于未来量子基础的探索和量子网络中。

据悉，量子纠缠是量子计算、密码学和传感领域最重要的资源之一。然而，纠缠也是脆弱的，它的潜在优势在实验中受到退相干效应的阻碍。

附：英文原文

Title: Protecting entanglement between logical qubits via quantum error correction

Author: Cai, Weizhou, Mu, Xianghao, Wang, Weiting, Zhou, Jie, Ma, Yuwei, Pan, Xiaoxuan, Hua, Ziyue, Liu, Xinyu, Xue, Guangming, Yu, Haifeng, Wang, Haiyan, Song, Yipu, Zou, Chang-Ling, Sun, Luyan

Issue&Volume: 2024-03-06

Abstract: Entanglement is one of the most important resources in quantum computing, cryptography and sensing. However, entanglement is also fragile, and its potential advantages are hindered by decoherence effects in experiments. Here we experimentally realize entangled logical qubits with a bosonic quantum module by encoding quantum information into spatially separated microwave modes. The entanglement is protected by repetitive quantum error correction, which improves the coherence time of the entangled logical qubits compared with their unprotected counterparts by 45%. In addition, we demonstrate the violation of the Bell inequality by the purified entangled logical qubits via independent error detection and post-selection on each logical qubit, resulting in measured Bell signals that surpass the classical bound. The protected entangled logical qubits could be applied in future explorations of quantum foundations and applications of quantum networks.

DOI: 10.1038/s41567-024-02446-8

Source: https://www.nature.com/articles/s41567-024-02446-8