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Experimental quantum repeater without quantum memory

Abstract

Quantum repeaters—important components of a scalable quantum internet—enable entanglement to be distributed over long distances. The standard paradigm for a quantum repeater relies on the necessary, demanding requirement of quantum memory. Despite significant progress, the limited performance of quantum memory means that making practical quantum repeaters remains a challenge. Remarkably, a proposed all-photonic quantum repeater avoids the need for quantum memory by harnessing the graph states in the repeater nodes. Here we perform an experimental demonstration of an all-photonic quantum repeater. By manipulating a 12-photon interferometer, we implement a 2 × 2 parallel all-photonic quantum repeater, and observe an 89% enhancement of entanglement-generation rate over standard parallel entanglement swapping. These results provide a new approach to designing repeaters with efficient single-photon sources and photonic graph states, and suggest that the all-photonic scheme represents an alternative path—parallel to matter-memory-based schemes—towards realizing practical quantum repeaters.

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Fig. 1: Overview of the all-photonic quantum repeater protocol.
Fig. 2: Experimental set-up.
Fig. 3: Experimental characterization of the four-photon GHZ state and PCM device.
Fig. 4: Experimental results for the 2 × 2 parallel all-photonic quantum repeater.

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

The authors thank H.-K. Lo for helpful discussions. This work was supported by the National Key Research and Development (R&D) Plan of China (grants 2018YFB0504300 and 2018YFA0306501), the National Natural Science Foundation of China (grants 11425417, 61771443 and U1738140), the Anhui Initiative in Quantum Information Technologies and the Chinese Academy of Sciences.

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Z.-D.L., F.X., Y.-A.C. and J.-W.P. conceived and designed the experiments. Z.-D.L., F.X. and Y.-A.C. designed and characterized the multiphoton optical circuits. Z.-D.L., R.Z., X.-F.Y., L.-Z.L., Y.H., Y.-Q.F. and Y.-Y.F. carried out the experiments. Z.-D.L., R.Z., F.X. and Y.-A.C. analysed the data. All authors discussed the results and wrote the manuscript. F.X., Y.-A.C. and J.-W.P. supervised the project.

Corresponding authors

Correspondence to Feihu Xu or Yu-Ao Chen or Jian-Wei Pan.

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The authors declare no competing interests.

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Li, ZD., Zhang, R., Yin, XF. et al. Experimental quantum repeater without quantum memory. Nat. Photonics 13, 644–648 (2019). https://doi.org/10.1038/s41566-019-0468-5

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