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Twin-field quantum key distribution over 830-km fibre

Abstract

Quantum key distribution (QKD) provides a promising solution for sharing information-theoretic secure keys between remote peers with physics-based protocols. According to the law of quantum physics, the photons carrying signals cannot be amplified or relayed via classical optical techniques to maintain quantum security. As a result, the transmission loss of the channel limits its achievable distance, and this has been a huge barrier towards building large-scale quantum-secure networks. Here we present an experimental QKD system that could tolerate a channel loss beyond 140 dB and obtain a secure distance of 833.8 km, setting a new record for fibre-based QKD. Furthermore, the optimized four-phase twin-field protocol and high-quality set-up make its secure key rate more than two orders of magnitude greater than previous records over similar distances. Our results mark a breakthrough towards building reliable and efficient terrestrial quantum-secure networks over a scale of 1,000 km.

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Fig. 1: Summary of recent long-distance QKD experiments beyond 400 km.
Fig. 2: Optical layout of the TF-QKD system.
Fig. 3: Results of source noise and phase drift with fibre channels.
Fig. 4: Interference visibility and MPI noise versus the intensity of the reference pulses.
Fig. 5: System stability over a distance of 833.80 km of quantum channel.
Fig. 6: Simulation and experimental results for the SKR and QBER.

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Data availability

All of the data that support the findings of this study are available in the main text or Supplementary Information. Source data are available from the corresponding authors on reasonable request.

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Acknowledgements

We acknowledge financial support from the National Key Research and Development Program of China (grant no. 2018YFA0306400), the National Natural Science Foundation of China (grants nos. 61622506, 61627820, 61822115, 61875181 and 61675189) and the 111 Project (D20031), and the Anhui Initiative in Quantum Information Technologies.

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Authors

Contributions

S.W., Z.-Q.Y., D.-Y.H. and Wei Chen (University of Science and Technology of China) developed the experimental set-up, performed the measurements and analysed the data. P.Y., G.-J.F.-Y., F.-X.W. and Z.Z. supported the experimental work. R.-Q.W., Y.Z. and Z.-Q.Y. provided the simulations. Wei Chen (Shanghai University & Jiangsu Hengtong Optical Fiber Technology Co. Ltd.) and Y.-G.Z. provided the ultra-low-loss fibres. P.V.M., A.V.D., D.-Y.H. and S.W. designed the low-noise detector. Wei Chen (University of Science and Technology of China), G.-C.G. and Z.-F.H. guided the work. S.W. and Z.-Q.Y. wrote the manuscript, with contributions from all the authors.

Corresponding authors

Correspondence to De-Yong He, Wei Chen or Zheng-Fu Han.

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Nature Photonics thanks Marco Lucamarini and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary sections, Figs. 1–7 and Tables 1–3.

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Wang, S., Yin, ZQ., He, DY. et al. Twin-field quantum key distribution over 830-km fibre. Nat. Photon. 16, 154–161 (2022). https://doi.org/10.1038/s41566-021-00928-2

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