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

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 ⁴⁰Ca⁺ 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^-1 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.