Yang Kui-Xing, Mao Ya-Li, Chen Hu, Dong Xiduo, Zhu Jiankun, Wu Jizhou, Li Zheng-Da
Shenzhen Institute for Quantum Science and Engineering, <a href="https://ror.org/049tv2d57">Southern University of Science and Technology</a>, Shenzhen 518055, China.
Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology, Center for Intense Laser Application Technology, and College of Engineering Physics, <a href="https://ror.org/04qzpec27">Shenzhen Technology University</a>, Shenzhen 518118, China.
Phys Rev Lett. 2024 Nov 22;133(21):210803. doi: 10.1103/PhysRevLett.133.210803.
Quantum networks aim to enable quantum information tasks among multiple parties. Quantum conference key agreement (QCKA) is a typical task in quantum networks, which distributes information-theoretically secure keys among multiple users. However, QCKA relying on directly distributing Greenberger-Horne-Zeilinger (GHZ) states over long distances faces significant challenges due to the fragility of these states. Measurement-device-independent QCKA (MDI-QCKA) based on distributing the postselected GHZ entanglement can address this issue and eliminate all loopholes in detection side channels. Here, by developing three-photon GHZ interference technology with high visibility among three independent coherent sources, we realized the first MDI-QCKA experiment over a 60 km fiber link, achieving a secret key rate of 45.5 bits/s. Our result represents a significant step towards practical long-distance QCKA using realistic devices. Moreover, the technology we developed opens the way to future multiparty quantum communications in quantum networks.
量子网络旨在实现多方之间的量子信息任务。量子会议密钥协商（QCKA）是量子网络中的一项典型任务，它在多个用户之间分发信息理论上安全的密钥。然而，由于格林伯格-霍恩-泽林格（GHZ）态的脆弱性，依赖于在长距离上直接分发GHZ态的QCKA面临重大挑战。基于分发后选择的GHZ纠缠的测量设备无关QCKA（MDI-QCKA）可以解决这个问题，并消除检测侧信道中的所有漏洞。在此，通过开发在三个独立相干源之间具有高可见度的三光子GHZ干涉技术，我们在60公里的光纤链路上实现了首个MDI-QCKA实验，实现了45.5比特/秒的密钥生成率。我们的结果代表了朝着使用实际设备实现实用的长距离QCKA迈出的重要一步。此外，我们开发的技术为量子网络中未来的多方量子通信开辟了道路。
