高效长寿命量子存储

This project will study quantum information storage in cold atoms. Through the Raman process, we shall inject a "write" laser beam to generate a Stokes photon and a "read" beam to generate an anti-Stokes photon, thus information carried by the write photon and stored in the quantum memory can be retrieved by the read process. By using degenerate sideband Raman cooling in a one-dimensional optical lattice, we shall obtain atoms in the vibrational ground state. This will prevent decoherence of the spin waves induced by the atoms' free motion and vibration. With an appropriate magnetic field to eliminate the Stark shift influence, we can prolong the information storage time. To improve the retrieval efficiency, an optical ring cavity will be used. In this way, we hope to realize a highly efficient and long-lived quantum memory system.

本项目将研究冷原子系统中的量子信息存储；利用原子的Raman过程，引入"写入"斯托克斯和"读取"反斯托克斯光，将写入光信息存入原子系综，再读出来，从而实现信息的存储与复现。利用一维光晶格中的简并边带Raman冷却使原子处于振动基态模式来消除原子自由运动和振动带来的自旋波的退相干，并配合合适的外加磁场来消除原子Stark频移的影响，提高量子信息的存储寿命。拟通过制备光学环形腔来提高量子信息的恢复效率，从而实现高恢复效率、长寿命的量子信息存储器。

我们完成了热原子和冷原子系统中基于电磁感应透明(EIT)的光存储实验。初步结果：热原子存储寿命30μs，读出效率20%；冷原子存储寿命100μs，读出效率2%。为了理解和优化EIT过程，我们分析了冷原子系统中EIT与Autler-Townews(AT)分裂在吸收和色散上的区别和过渡，并通过原子数Rabi振荡来区分EIT分裂和AT信号，该方法更为简单和直接。为了提高存储寿命和效率，我们初步搭建了垂直腔面发射激光（VCSEL）锁相系统，光晶格和大光学厚度近为1000的一维光阱，为将来实现高恢复效率、长寿命的量子信息存储器奠定基础。