频率变化的光场对双光子过程中量子纠缠的调控

运用量子信息熵理论研究了二能级原子与频率随时间变化的相干态光场作用的双光子过程中纠缠度演化，主要讨论了光场频率随时间作正弦调制和脉冲调制两种情况下，纠缠随时间的演化特性. 当光场频率随时间作正弦调制时，原子与光场的纠缠度明显增大，并保持高纠缠度. 通过改变光场频率调制的频率β和振幅α，发现原子与光场纠缠度的演化过程对调制的振幅更加敏感. 当光场频率随时间作脉冲调制时，在纠缠度最大值处开始加脉冲比在最小值处加脉冲能够更快、更容易实现原子与光场纠缠度的提高和稳定. 脉冲调制的突变使 关键词： 纠缠 场熵 相干态 双光子Jaynes-Cummings模型

The influence of the field frequency modulation on quantum entanglement via two-photon process

The entanglement degree is investigated by means of the entropy theory between a two-level atom and a coherent field with varying frequency via two-photon transition. We restrict our attention to two cases, the field frequency varying with time in the forms of sine and rectangle. When the field frequency varies with time in the form of sine, the entanglement degree will increase sharply and maintain high values. By changing the amplitude α and angular frequency β of the field-frequency variation respectively, we find that the evolution process is more sensitive to the former. In the rectangular modulation case, different results will be produced when the pulses appear at different time. Comparing the pulses appearing at every minimum value with that at every maximum value, the entanglement degree will increase and reach stability more quickly and easily in the lattev case. The sudden change caused by the rectangular modulation is particularly beneficias to the control of the value of the field entropy.