Affiliation:
1. State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto‐Electronics Taiyuan 030006 China
2. Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan 030006 China
Abstract
AbstractAtomic spin‐wave (SW) memory is a building block for quantum repeater. However, due to decoherence caused by atomic motions and magnetic‐field gradients, SW retrieval efficiency decays with storage time. Slow magnetic‐field fluctuations (SMFFs) lead to shot‐to‐shot phase noises of SWs, but have not been considered in previous repeater protocols. Here, a SW model including a homogeneous phase noise caused by SMFFs is developed, and then revealed that such phase noise induces decoherence of single‐excitation entanglement between two atomic ensembles in a repeater link. For verifying this conclusion, single‐excitation entanglement between two SWs in a cold atomic ensemble is experimentally prepared and observed entanglement decoherence induced by SMFFs. Limited by SMFFs, the evaluated lifetime of the single‐excitation entanglement over a repeater link is ≈135 ms, even if the link uses optical‐lattice atoms as nodes. Then an approach that may overcome such limitations and extend this lifetime to ≈1.7 s is presented.
Funder
National Natural Science Foundation of China
Fund for Shanxi Key Subjects Construction
Subject
Electrical and Electronic Engineering,Computational Theory and Mathematics,Condensed Matter Physics,Mathematical Physics,Nuclear and High Energy Physics,Electronic, Optical and Magnetic Materials,Statistical and Nonlinear Physics