原子运动与场频率变化操控下的场熵演化及量子态制备

在旋波近似下,同时考虑原子运动和光场频率随时间作正弦函数变化,研究了二能级原子与单模辐射场相互作用系统中场的量子约化熵的演化规律.运用数值计算的方法分别给出了在不考虑原子的运动和考虑原子的运动的情况下场熵随时间的演化曲线,讨论了原子运动、场模结构、场频率的幅值和角频率变化对场熵的影响.根据Schmidt分解定理,解析制备了光场与原子的纠缠态、光场偶数态及原子相干叠加态,获得了调控和制备上述量子态的系统参量.研究结果表明:场熵的演化受场频率变化的调制,场频率变化的幅值增大会削弱场与原子的相互作用,场熵演化的周期性与场频率变化一致|原子的运动导致了场熵演化周期加倍|在场频率变化的角频率一定的情形下,场熵演化规律与场模结构参量的奇偶性有关|无论原子运动与否,都可周期性制备场-原子的近似EPR态.

Evolution of the Field Entropy and Preparation of Quantum States in the Control of Atomic Motion and Field-frequency Variation

 In the rotating-wave approximation,the evolution of the field quantum entropy in the system that consists of a two-level atom interacting with a single-mode field was studied,considering the atomic motion and the field frequency varying with the time in the form of sine-function at the same time.In two cases of neglecting atomic motion and considering atomic motion,figures of the time evolutions of the field entropy were plotted respectively using numerical calculations.Influences of the atomic motion,the field-model structure parameter,amplitude and angular frequency of the field-frequency variation on the field entropy were also discussed.The atom-field entangled states,field fock states and atomic high fidelity states were prepared by analytic method according to the decomposition theorem of Schmidt,and the related system parameters of these quantum states operation were acquired.The results show that:the time evolution behavior of the field entropy is modulated by the frequency variation of field|the interaction between the field and atom will weaken with the increase of the amplitude of variation of the field frequency|the period of the field entropy agrees with the period of field-frequency variation|the atomic motion will result in the period of the field entropy doubled|the evolution of the field entropy is related to the parity of field-mode structure parameter|the approximate EPR states of field-atom can be prepared periodically whether the atom moves or not.