基于EuCl_(3)·6H_(2)O晶体的光存储

Atomic frequency comb optical memory in EuCl_(3)·6H_(2)O crystal

量子存储器是构建未来大规模量子网络的核心器件.由于具有超长的量子相干寿命,稀土掺杂晶体逐渐成为最有希望实现实用量子存储的材料之一.然而掺杂晶体中不可避免的晶格畸变限制了该类材料的吸收深度和存储效率.纯稀土化合物晶体则同时满足了低晶格畸变和高稀土离子密度的需求,有望实现高光存储效率. EuCl_(3)·6H_(2)O晶体是目前研究较多的一种纯稀土化合物晶体,已经实现了低于超精细能级间距的光学非均匀展宽,并且理论预测的自旋相干寿命可达1000 s,是一种颇具潜力的量子存储材料.目前光存储或量子存储功能仅仅在稀土掺杂晶体中实现过,尚无实验报道纯稀土化合物晶体中的光存储现象.本文报告了在EuCl_(3)·6H_(2)O晶体中实现了原子频率梳型光存储.通过降温法生长得到了EuCl_(3)·6H_(2)O单晶,实验测得其~7F_0→~5D_0跃迁相干时间为55.7μs,存储时间1μs时的存储效率为1.71%,展现了这种材料实现光量子存储的原理可行性.通过分析温度依赖的吸收线频率移动,指出在这一材料中实现高效率光存储的主要挑战在于高效率的光谱烧孔.

Quantum memory is a crucial component for the large-scale quantum networks.Rare-earth-ion doped crystals have been a promising candidate for the practical quantum memory because of its very long coherence time.However,doped ions cause unwanted lattice distortion,and consequently reduce the optical depth and the storage efficiency.The stoichiometric rare-earth crystals have low lattice distortion and high rare earth ion density,and thus are expected to enable high-efficiency storage.EuCl_(3)·6H_(2)O is a promising material for quantum memory applications because its optical inhomogeneous broadening can be smaller than its hyperfine splitting and the theoretically predicted spin coherence time is up to 1000 seconds.Despite the numerous efforts in solid-state quantum memory based on rare-earth ion doped crystals,optical memory and quantum memory have not been implemented with stoichiometric rare-earth crystals yet.Here,we report the atom frequency comb optical storage using a EuCl_(3)·6H_(2)O crystal.A coherence time of 55.7μs is obtained by photon echo measurements on 7F0→5D0 storage efficiency of 1.71%at a storage time of 1μs,showing the potential capability of optical quantum storage of this material.Based on the analysis of the line shift of 7F0→5D0 highlight the challenge of achieving high-efficiency optical pumping in this material,which imposes a limit on the achievable efficiency.