Cao Yuan, Li Yu-Huai, Yang Kui-Xing, Jiang Yang-Fan, Li Shuang-Lin, Hu Xiao-Long, Abulizi Maimaiti, Li Cheng-Long, Zhang Weijun, Sun Qi-Chao, Liu Wei-Yue, Jiang Xiao, Liao Sheng-Kai, Ren Ji-Gang, Li Hao, You Lixing, Wang Zhen, Yin Juan, Lu Chao-Yang, Wang Xiang-Bin, Zhang Qiang, Peng Cheng-Zhi, Pan Jian-Wei
Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China.
Shanghai Branch, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China.
Phys Rev Lett. 2020 Dec 31;125(26):260503. doi: 10.1103/PhysRevLett.125.260503.
Measurement-device-independent quantum key distribution (MDI-QKD), based on two-photon interference, is immune to all attacks against the detection system and allows a QKD network with untrusted relays. Since the MDI-QKD protocol was proposed, fiber-based implementations aimed at longer distance, higher key rates, and network verification have been rapidly developed. However, owing to the effect of atmospheric turbulence, MDI-QKD over a free-space channel remains experimentally challenging. Herein, by developing a robust adaptive optics system, high-precision time synchronization and frequency locking between independent photon sources located far apart, we realized the first free-space MDI-QKD over a 19.2-km urban atmospheric channel, which well exceeds the effective atmospheric thickness. Our experiment takes the first step toward satellite-based MDI-QKD. Moreover, the technology developed herein opens the way to quantum experiments in free space involving long-distance interference of independent single photons.
基于双光子干涉的测量设备无关量子密钥分发（MDI-QKD）对针对检测系统的所有攻击具有免疫能力，并允许构建带有不可信中继的量子密钥分发网络。自MDI-QKD协议提出以来，旨在实现更长距离、更高密钥率和网络验证的基于光纤的实现方案得到了迅速发展。然而，由于大气湍流的影响，在自由空间信道上实现MDI-QKD在实验上仍具有挑战性。在此，通过开发一个强大的自适应光学系统、实现位于远处的独立光子源之间的高精度时间同步和频率锁定，我们在一条19.2公里的城市大气信道上实现了首个自由空间MDI-QKD，这一距离远超有效大气厚度。我们的实验朝着基于卫星的MDI-QKD迈出了第一步。此外，本文所开发的技术为涉及独立单光子长距离干涉的自由空间量子实验开辟了道路。
