Metropolitan-scale ion-photon entanglement via a quantum network node with hybrid multiplexing enhancements.

Cui, Z-B; Wang, Z-Q; Lai, P-C; Wang, Y; Shi, J-X; Liu, P-Y; Sun, Y-D; Tian, Z-C et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Quantum network and quantum repeater are promising ways to scale up a quantum information system. In a functional quantum network, it is required that the distribution rate of heralded remote entanglement should be higher than the decoherence rate of each local node. A promising scheme to accelerate the remote entanglement distribution is through multiplexing enhancement. In this work, we experimentally realize a multiplexed quantum network node based on a chain of <sup>40</sup>Ca<sup>+</sup> ions. We employ a hybrid multiplexing scheme in which maximally 44 time-bin modes are generated and sent through a long fiber to boost the entangling rate. Via this scheme, we can generate heralded ion-photon entanglement with a success rate of 4.28 s<sup>-1</sup> over a 12 km fiber. In addition, a dual-type framework is utilized to protect quantum information from the destructive ion-photon entangling attempts and a memory coherence time of 366 ms is achieved, which has exceeded the entanglement generation time.