与双模场依赖强度耦合下多光子通道中原子比 特周期量子回声产生和调控

旋波近似条件下,运用全量子理论研究了与双模相干光场依赖强度耦合多光子通道中原子比特周期量子回声的产生和控制. 采用数值计算的方法,讨论了双模相干光场平均光子数分布形式、分布范围及原子跃迁时吸收(或发射)的光子数k对原子比特态保真度演化的影响,获得了产生和控制原子比特周期量子回声的系统参量;根据纠缠理论,分析了原子比特态保真度演化与原子约化熵演化的关联. 结果表明:在k=1的双光子过程中,调控光场平均光子数呈对称或不对称分布,当它的取值在一定范围内,原子比特保持良好的相干性和保真度,产生周期量子回声; 对于k≥2的多光子过程,原子比特与双模相干光场始终处于最大纠缠,因此导致了原子比特始终处于部分失真状态,不产生周期量子回声. 本研究揭示了周期量子回声产生的物理实质是原子比特与光场周期性退纠缠.

Preparation and Control for Periodic Quantum Echo of Atom Bit via Two-mode Light Field Intensity-dependent Coupling Multiphoton Channel

In the rotating-wave approximation, the produce and control for periodic quantum echo of atom bit interacting with a two-mode coherent light field is investigated via intensity-dependent coupling multiphoton channel by means of the full quantum theory. The effects on the evolution of the fidelity of atom bit for both the distribution form and distribution range of the average photon number of the two-mode coherent light field, and the photon number k of absorbed (emitted) as the atoms transition are discussed by numerical calculations, respectively. The system parameter of preparation and control for periodic quantum echo of atomic bits are obtained. According to the entanglement theory, the relation of the fidelity of atom bit with atomic reduced entropy is analyzed. The results show that atom bitkeeps good coherence and fidelity, and will produce periodic quantum echo for the two photon process as k=1, by regulation average photon number of the light fields being symmetrical or asymmetrical distribution and its value in a certain range. For k≥2 multiphoton process, the atom bit is always in a maximally entangled with the two-mode coherent light field so that the atom bit is in a state of partial distortion without periodic quantum echo. It is shown that the physical nature of the periodic quantum echo produce is periodic disentangled between the atom bit and the light field.