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Twin-field quantum key distribution over a 511 km optical fibre linking two distant metropolitan areas

Nature Photonics volume 15, pages 570–575 (2021)Cite this article

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Abstract

The basic principle of quantum mechanics1 guarantees the unconditional security of quantum key distribution (QKD)2,3,4,5,6 at the cost of forbidding the amplification of a quantum state. As a result, and despite remarkable progress in worldwide metropolitan QKD networks7,8 over the past decades, a long-haul fibre QKD network without a trusted relay has not yet been achieved. Here, through the sending-or-not-sending protocol9, we achieve twin-field QKD10 and distribute secure keys without any trusted repeater over a 511 km long-haul fibre trunk that links two distant metropolitan areas. The fibre trunk contains 12 fibres in the cable, three of which are used for the quantum channel, optical synchronization and frequency locking, respectively. The remaining nine are used for classical fibre communication. Our secure key rate is around three orders of magnitude greater than that expected if the previous QKD field-test system was applied over the same length. Efficient quantum-state transmission and stable single-photon interference over such a long-haul deployed fibre pave the way to large-scale fibre quantum networks.

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Fig. 1: Field deployment of SNS-TF-QKD.
Fig. 2: Fluctuation of deployed fibre.
Fig. 3: Secure key rates of the SNS-TF-QKD experiment.

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Acknowledgements

This work was supported by the National Key R&D Program of China (grant numbers 2020YFA0309800, 2017YFA0303900 and 2017YFA0304000), the National Natural Science Foundation of China, the Chinese Academy of Sciences (CAS), the Key R&D Plan of Shandong Province (grant numbers 2019JZZY010205 and 2020CXGC010105), the Taishan Scholar Program of Shandong Province and the Anhui Initiative in Quantum Information Technologies.

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  1. These authors contributed equally: Jiu-Peng Chen, Chi Zhang.

Authors and Affiliations

  1. Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, China

    Jiu-Peng Chen, Chi Zhang, Yang Liu, Yu-Huai Li, Hui Liu, Hai-Feng Jiang, Teng-Yun Chen, Qiang Zhang & Jian-Wei Pan

  2. Jinan Institute of Quantum Technology, Jinan, China

    Jiu-Peng Chen, Chi Zhang, Yang Liu, Cong Jiang, Zhi-Yong Han, Shi-Zhao Ma, Fei Zhou & Xiang-Bin Wang

  3. State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China

    Cong Jiang, Xiao-Long Hu & Xiang-Bin Wang

  4. State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China

    Wei-Jun Zhang, Hao Li, Li-Xing You & Zhen Wang

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  1. Jiu-Peng Chen
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Contributions

Y.L., X.-B.W., Q.Z. and J.-W.P. conceived the research. W.-J.Z., H.Li., L.-X.Y. and Z.W. developed the SNSPD. J.-P.C., C.Z., Y.-H.L. and H.-F.J. implemented the stable laser system and the wavelength-locking system in the field. J.-P.C., C.Z., Z.-Y.H. and Q.Z. performed the field experiments. C.J., X.-L.H. and X.-B.W. developed the theory and calculated the secure key rate. J.-P.C., S.-Z.M., H.Liu., Z.-Y.H., F.Z. and T.-Y.C. arranged and tested the field fibre. All authors performed the data analysis and prepared the manuscript.

Corresponding authors

Correspondence to Xiang-Bin Wang, Qiang Zhang or Jian-Wei Pan.

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The authors declare no competing interests.

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Peer review information Nature Photonics thanks Charles C.-W. Lim and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–5, Discussion and Tables 1–5.

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Chen, JP., Zhang, C., Liu, Y. et al. Twin-field quantum key distribution over a 511 km optical fibre linking two distant metropolitan areas. Nat. Photon. 15, 570–575 (2021). https://doi.org/10.1038/s41566-021-00828-5

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