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A photonic entanglement filter with Rydberg atoms


Devices capable of deterministically manipulating photonic entanglement are of paramount importance, because photons are ideal messengers for quantum information. However, due to the non-interacting nature of photons, many photonic quantum operations have only been demonstrated using probabilistic linear-optical approaches, leading to an overwhelming resource overhead and poor scalability. Here we report a novel entanglement filter that transmits the desired photonic entangled state and blocks unwanted ones. In contrast to previous probabilistic approaches, our experiment exploits the strong and controllable photon–photon interaction enabled by Rydberg atoms, so the filtering of undesired states succeeds in every experimental trial. Photonic entanglement with near-unity fidelity can be extracted from an input state with an arbitrarily low initial fidelity. The protocol is inherently robust, and succeeds both in the Rydberg blockade regime and in the interaction-induced dissipation regime. Such an entanglement filter opens new routes towards achieving scalable photonic quantum information processing with multiple ensembles of Rydberg atoms.

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Fig. 1: Illustration of the experimental protocol.
Fig. 2: Blockade-based EF.
Fig. 3: Extracting entanglement from an arbitrarily noisy input.
Fig. 4: Interaction-induced two-body decoherence.
Fig. 5: EF via dissipative quantum evolution.

Data availability

Data supporting the plots within this paper are available through Zenodo at Further information is available from the corresponding author upon reasonable request.

Code availability

The code used in this study is available from the corresponding author upon reasonable request.


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We thank D. Su and K. Zhang for valuable discussions and C. Du, F.-Y. Kuang, Y. Cai and D.-S. Xiang for experimental assistance. This work was supported by the National Key Research and Development Program of China (grant no. 2021YFA1402003), the National Natural Science Foundation of China (grants nos. U21A6006, 12004127 and 12104173) and the Fundamental Research Funds for the Central Universities (HUST). Y.C. is supported by the National Natural Science Foundation of China (grant no. U2141237). T.S. is supported by the National Key Research and Development Program of China (grant no. 2017YFA0718304) and the National Natural Science Foundation of China (grants nos. 11974363, 12135018 and 12047503).

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Authors and Affiliations



G.-S.Y., B.X. and S.S. built the experimental set-up, performed the measurements and carried out data analysis. Y.C., G.-S.Y. and T.S. developed the theoretical model and accomplished numerical simulations. L.L. conceived the idea and supervised the experiment. G.-S.Y., Y.C. and L.L. wrote the paper with input from all authors.

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Correspondence to Lin Li.

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Ye, GS., Xu, B., Chang, Y. et al. A photonic entanglement filter with Rydberg atoms. Nat. Photon. 17, 538–543 (2023).

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