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Entanglement of three quantum memories via interference of three single photons


Quantum memory networks as an intermediate stage in the development of a quantum internet1 will enable a number of significant applications2,3,4,5. To connect and entangle remote quantum memories, it is best to use photons. In previous experiments6,7,8,9,10,11,12,13, entanglement of two memory nodes has been achieved via photon interference. Going beyond the state of the art by entangling many quantum nodes at a distance is highly sought after. Here, we report the entanglement of three remote quantum memories via three-photon interference. We employ laser-cooled atomic ensembles and make use of a ring cavity to enhance the overall efficiency of our memory–photon entanglement. By interfering three single photons from three separate set-ups, we create entanglement of three memories and three photons. Then, by measuring the photons and applying feed-forward, we achieve heralded entanglement between the three memories. Our experiment may be employed as a building block to construct larger and complex quantum networks14,15.

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This work was supported by National Key R&D Program of China (no. 2017YFA0303902), Anhui Initiative in Quantum Information Technologies, National Natural Science Foundation of China, and the Chinese Academy of Sciences.

Author information

X.-H.B. and J.-W.P. conceived and designed the experiment. B.J. and X.-J.W. mainly carried out the experiment and collected the data with assistance from all other authors. B.J., X.-J.W. and X.-H.B. analysed the data. B.J., X.-J.W., X.-H.B. and J.-W.P. wrote the paper with input from all other authors. X.-H.B. and J.-W.P. supervised the whole project.

Competing interests

The authors declare no competing interests.

Correspondence to Xiao-Hui Bao or Jian-Wei Pan.

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Fig. 1: Experiment layout.
Fig. 2: Characterization of a single entangled atom–photon pair.
Fig. 3: Characterization of the sixfold entanglement |GHZ6〉.
Fig. 4: Characterization of the three-memory entanglement |GHZ3〉.