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Implementation of quantum key distribution surpassing the linear rate-transmittance bound

Nature Photonics volume 14, pages 422–425 (2020)Cite this article

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Abstract

Quantum key distribution (QKD)1,2 offers a long-term solution to secure key exchange. Due to photon loss in transmission, it was believed that the repeaterless key rate is bounded by a linear function of the transmittance, O(η) (refs. 3,4), limiting the maximal secure transmission distance5,6. Recently, a novel type of QKD scheme has been shown to beat the linear bound and achieve a key rate performance of \(O(\sqrt{\eta })\) (refs. 7,8,9). Here, by employing the laser injection technique and the phase post-compensation method, we match the modes of two independent lasers and overcome the phase fluctuation. As a result, the key rate surpasses the linear bound via 302 km and 402 km commercial-fibre channels, over four orders of magnitude higher than existing results5. Furthermore, our system yields a secret key rate of 0.118 bps with a 502 km ultralow-loss fibre. This new type of QKD pushes forward long-distance quantum communication for the future quantum internet.

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Fig. 1: Schematic of PM-QKD.
Fig. 2: Experimental set-up.
Fig. 3: Experimental parameters and results.

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Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

We thank H. Zhou for insightful discussions. This work was supported by the National Key R&D Program of China (2017YFA0303903), the Chinese Academy of Science, the National Fundamental Research Program, the National Natural Science Foundation of China (grants 11875173, 61875182 and 11674193) and Anhui Initiative in Quantum Information Technologies and Fundamental Research Funds for the Central Universities (WK2340000083).

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Author notes

  1. These authors contributed equally: Xiao-Tian Fang, Pei Zeng, Hui Liu.

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, Anhui, China

    Xiao-Tian Fang, Hui Liu, Mi Zou, Yu-Ao Chen, Qiang Zhang, Cheng-Zhi Peng, Teng-Yun Chen & Jian-Wei Pan

  2. CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, China

    Xiao-Tian Fang, Hui Liu, Mi Zou, Yu-Ao Chen, Qiang Zhang, Cheng-Zhi Peng, Teng-Yun Chen & Jian-Wei Pan

  3. Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing, China

    Pei Zeng, Weijie Wu & Xiongfeng Ma

  4. QuantumCTek Corporation Limited, Hefei, Anhui, China

    Yan-Lin Tang, Ying-Jie Sheng, Yao Xiang & Cheng-Zhi Peng

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

    Weijun Zhang, Hao Li, Zhen Wang & Lixing You

  6. Corning Incorporated, Corning, NY, USA

    Ming-Jun Li & Hao Chen

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  1. Xiao-Tian Fang
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Contributions

X.M., T.-Y.C. and J.-W.P. conceived the research. Y.-A.C. Q.Z., C.-Z.P., X.M., T.-Y.C. and J.-W.P. designed the experiment. X.-T.F., H.Liu and T.-Y.C. carried out the experiment. P.Z., W.W. and X.M. performed the protocol security analysis and data post-processing. M.Z. and Y.-L.T. assisted with the experiment scheme discussion and verification. Y.-J.S. designed and developed the voltage pulse generator. Y.X. programmed the field-programmable gate array logic. W.Z., H.Li, Z.W. and L.Y. designed and fabricated the superconducting nanowire single-photon detector. M.-J.L. and H.C. provided the ultralow-loss fibres. P.Z., X.-T.F., H.Liu, X.M., T.-Y.C. and J.-W.P. co-wrote the manuscript, with input from the other authors. All authors discussed the results and proofread the manuscript.

Corresponding authors

Correspondence to Xiongfeng Ma, Teng-Yun Chen or Jian-Wei Pan.

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Supplementary Information

Supplementary Figs. 1–4, discussion, equations 1–28 and Tables 1–10.

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Fang, XT., Zeng, P., Liu, H. et al. Implementation of quantum key distribution surpassing the linear rate-transmittance bound. Nat. Photonics 14, 422–425 (2020). https://doi.org/10.1038/s41566-020-0599-8

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