量子梯度存储器中极化声子演化的研究

Analysis of Polaritonic in the Quantum Gradient-echo Memory

本文从量子梯度回声存储器(GEM)存储光脉冲时的麦克斯韦-布洛赫方程组出发,推导了GEM在k空间的极化声子描述及其满足的微分方程。我们解出了k空间行波通解,得到极化声子演化规律的数学表达式,加深了对已有的实验和数值模拟结果的理解。然后,我们考虑了实际原子系综量子态的退相干效应,解出了带有退相干参数的通解,发现了退相干效应对存储失真影响的定量关系。基于此,我们提出了GEM存储的一个优化方案。这个优化方案不但使存储的保真度有所提高,还缩短了翻转梯度外场与回声脉冲读取的时间间隔,为量子存储器走向实际应用提供了理论帮助。

Start from Maxwell-Bloch equations, we deduced the polaritonic description of the gradient-echo memory（GEM）in the k space and its differential equations. Solving the differential equations, we got the wave solution of evolution of the decoherence-free polaritonic mode inside the GEM system, whcih clearly illustrated the result of experiment and numerical simulation that had been done. In the same way, we took decoherence into account, and solved the differential equation with the parameter of decoherence rate. We found the contribution that the decohence made to the distortion within echo-pulse. Based on our analysis, we optimized the storage procedure of GEM. It not only improves the fidelity of echo-pulse, but also reduces the duration between manipulation of gradient field and output of echo-pulse, which will make sense in practical application of GEM in the future.