Abstract
To fully exploit the potential of quantum technologies, quantum networks are needed to link different systems, enhancing applications in computing, cryptography and metrology. Central to these networks are quantum relays that can facilitate long-distance entanglement distribution and quantum communication. In this work, we present a modular and scalable quantum relay architecture using a high-quality single-photon source. The proposed network incorporates three untrusted intermediate nodes and is capable of a repetition rate of 304.52 MHz. We use a measurement-device-independent protocol to demonstrate secure key establishment over fibres covering up to 300 km. This study highlights the potential of single-photon sources in quantum relays to enhance information transmission, expand network coverage and improve deployment flexibility, with promising applications in future quantum networks.
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Data availability
All data are available from the corresponding authors upon reasonable request. Source data are provided with this paper.
Code availability
The code for simulating the key rate is available from the corresponding authors upon reasonable request.
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Acknowledgements
This work was supported by the Innovation Program for Quantum Science and Technology (grant numbers 2021ZD0300702 to T.-Y.C., 2021ZD0301300-1 to T.-Y.C., 2021ZD0300804 to X.M., 2021ZD0301400 to Y.-M.H., 2021ZD0300204 to Y.-H.H., 2021ZD0300800 to Q.Z., X.-P.X. and M.-Y.Z.), the National Natural Science Foundation of China (grant numbers 12174216 to X.M., 12022402 to Y.-M.H. and 62474168 to Y.-H.H.), the Anhui Initiative in Quantum Information Technologies (grant number AHY060000 to C.-Y.L.), the Shanghai Municipal Science and Technology Major Project (grant number 2019SHZDZX01 to C.-Y.L. and Y.-H.H.), the Chinese Academy of Sciences (CAS) Project for Young Scientists in Basic Research (grant number YSBR-112 to Y.-H.H.), the Youth Innovation Promotion Association of CAS (grant number Y2023128 to Y.-M.H.), the Independent Deployment Project of HFNL (grant number ZB2025010300 to Y.-M.H.), the Strategic Priority Research Program of CAS (grant number XDA0520401 to Y.-M.H.), the China Postdoctoral Science Foundation (grant number 2022T150628 to X.D.) and the Postdoctoral Research Project in Anhui Province (grant number 2024C890 to X.Y.). C.-Y.L. acknowledges support from the New Cornerstone Science Foundation. T.-Y.C. acknowledges support from the Anhui Initiative in Quantum Information Technologies.
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T.-Y.C., X.M. and J.-W.P. conceived the research. M.Z., Y.-M.H., T.-Y.C., Y.H., X.M., C.-Y.L. and J.-W.P. designed the experiment. M.Z. and Y.-M.H. carried out the experiment and performed data post-processing. Y.H. and X.M. performed the protocol security analysis and data post-processing. Y.H., Y.-M.H. and B.-C.L. performed a theoretical interference analysis. J.-Y.Z., R.-Z.L. and Y.-H.H. grew and fabricated the quantum dot samples. Y.-P.G., X.D., G.-Y.Z., H.W. and C.-Y.L. contributed to the generation of single-photon sources. M.-C.X. and Z.N. fabricated the cavity mirror. X.Y., M.-Y.Z., X.-P.X. and Q.Z. contributed to fluorescence upconversion. W.-X.P. and H.-T.Z. assisted with the experiment scheme discussion. D.Q. and X.J. developed the polyimide circuit board and maintained it for frequency locking. Y.H., X.M., M.Z., Y.-M.H., T.-Y.C., C.-Y.L. and J.-W.P. co-wrote the paper, with input from the other authors. All authors discussed the results and proofread the paper. J.-W.P. supervised the project.
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Zou, M., He, YM., Huang, Y. et al. Realization of an untrusted intermediate relay architecture using a quantum dot single-photon source. Nat. Phys. (2025). https://doi.org/10.1038/s41567-025-03005-5
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DOI: https://doi.org/10.1038/s41567-025-03005-5
