The basic principle of quantum mechanics guarantee the unconditional security of quantum key distribution (QKD) at the cost of inability of amplification of quantum state. As a result, despite remarkable progress in worldwide metropolitan QKD networks over the past decades, long haul fiber QKD network without trustful relay has not been achieved yet. Here, through sending-or-not-sending (SNS) protocol, we complete a twin field QKD (TF-QKD) and distribute secure keys without any trusted repeater over a 511 km long haul fiber trunk linking two distant metropolitans. Our secure key rate is around 3 orders of magnitudes greater than what is expected if the previous QKD field test system over the same length were applied. The efficient quantum-state transmission and stable single-photon interference over such a long distance deployed fiber paves the way to large-scale fiber quantum networks.
@article{arxiv.2102.00433,
title = {Twin-Field Quantum Key Distribution over 511 km Optical Fiber Linking two Distant Metropolitans},
author = {Jiu-Peng Chen and Chi Zhang and Yang Liu and Cong Jiang and Wei-Jun Zhang and Zhi-Yong Han and Shi-Zhao Ma and Xiao-Long Hu and Yu-Huai Li and Hui Liu and Fei Zhou and Hai-Feng Jiang and Teng-Yun Chen and Hao Li and Li-Xing You and Zhen Wang and Xiang-Bin Wang and Qiang Zhang and Jian-Wei Pan},
journal= {arXiv preprint arXiv:2102.00433},
year = {2021}
}