Heralded Entanglement Distribution Between Two Spin‐Wave Memories Using Temporally Multiplexed Scheme

Abstract

AbstractThe elementary link, which is formed by entanglement between two remote atomic ensembles, is a fundamental component of Duan–Lukin–Cirac–Zoller (DLCZ) quantum repeater. For practical realization of quantum repeaters, it is required that entanglement between two atomic‐ensemble‐based memories can be generated with high rates and retrieved with high efficiencies. However, so far, such quantum‐repeater links remain challenge in experiments. Here, heralded entanglement distribution between atomic‐ensemble‐based memories is demonstrated via temporally multiplexed scheme. A train of 12 write pulses in time is applied to a cloud of cold atoms along different directions, which generates temporally multiplexed pairs of Stokes photons and spin waves via DLCZ processes. The Stokes fields propagating in the two spatial modes, which are paired with two spin waves are combined to perform a single‐photon Bell‐state measurement. A successful detection projects the two spin waves into a single‐excitation entanglement, which represents entanglement distribution in an elementary link. Compared with single‐mode storage scheme, the temporally multiplexed scheme gives rise to a 11.8‐fold increase in entanglement generation rate. By using cavity‐enhanced scheme, spin waves stored in the atoms are retrieved on demand and the retrieval efficiencies are up to 70%, which is beneficial for the subsequent entanglement swapping between adjacent links.