Multiplexed spin-wave-photon entanglement source using temporal multimode memories and feedforward-controlled readout

摘要

A source that can generate atom-photon quantum correlations or entanglement based on a quantum memory is a basic building block of quantum repeaters (QRs). To achieve high entanglement generation rates in ensemblebased QRs, spatial-, temporal-, and spectral-multimode memories are needed. Previous temporal-multimode memories are based on rephasing mechanisms in inhomogeneously broadened media. Here, by applying a train of write pulses in time, with each pulse coming from a different direction, to a homogeneously broadened atomic ensemble to induce Duan-Lukin-Cirac-Zoller-like Raman processes, we prepare up to 19 pairs of modes, namely, one spin-wave mode and one photonic time bin. Spin-wave-photon (i.e., atom-photon) entanglement is probabilistically produced in these mode pairs. Based on the stored spin-wave modes together with feedforwardcontrolled readout, we build a temporally multiplexed source and then demonstrate an 18.8-fold increase in the probability of the generation of spin-wave-photon entanglement compared to the sources that use individual modes. The measured Bell parameter for the multiplexed source is 2.30 ± 0.02, and the memory lifetime is 30 μs.