Multiqubit entanglement is an indispensable resource for quantum information science. In particular, the entanglement of photons is of conceptual interest due to its implications in measurement-based quantum computing, communication and metrology. The traditional way of spontaneous parametric downconversion already demonstrates the entanglement of up to a dozen photons but is hindered by its probabilistic nature. Here we experimentally demonstrate an efficient approach for multiphoton generation with a Rydberg superatom, a mesoscopic atomic ensemble under Rydberg blockade. Using it as an efficient single-photon interface, we iterate the photon creation process that gives rise to a train of single photons entangled in the time-bin degree of freedom. Photon correlations verify entanglement up to six qubits. The overall efficiency to detect one photon is 9.4%. After correcting the measurement inefficiencies, we obtain a scaling factor of 27%, surpassing previous results and paving the way for larger-scale photonic entanglement.
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This work was supported by the National Key R&D Program of China (nos. 2017YFA0303902 and 2020YFA0309804); Anhui Initiative in Quantum Information Technologies, National Natural Science Foundation of China; and the Chinese Academy of Sciences.
The authors declare no competing interests.
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Yang, CW., Yu, Y., Li, J. et al. Sequential generation of multiphoton entanglement with a Rydberg superatom. Nat. Photon. 16, 658–661 (2022). https://doi.org/10.1038/s41566-022-01054-3