存在相位退相干时原子与光场相互作用的纠缠演化和保持

应用全量子理论研究了存在相位退相干时单模相干光场与一个二能级原子相互作用系统纠缠的时间演化规律;分别讨论了原子—光场耦合常数、光场的平均光子数以及失谐量的大小对场与原子纠缠的影响.结果表明:随着原子—光场耦合常数的增大和光场平均光子数的增加,系统纠缠的振荡频率都会明显增大.不存在相位退相干时,纠缠的时间演化明显受到失谐量的影响,若选取适当的失谐量,系统的纠缠可长时间保持在最大纠缠态.若考虑相位退相干的影响,则在共振情况下系统纠缠的时间演化是一个逐渐衰减的过程,且最终衰减到零;但若存在适当的失谐量,则在初始一段时间内系统的纠缠也是一个波动幅度逐渐衰减的过程,但随着时间的演化,失谐量抵消了相位退相干的影响,使系统的纠缠不再衰减到零.如果增大失谐量,纠缠在初始一段时间内波动的幅度会相应的减小,并且纠缠趋于稳定的时间也随着失谐量的增大而缩短;当失谐量适当时,系统可保持在纠缠相对较大的状态而无消纠缠态.

The time-evolution of entanglement in the interacting System of the atom and coherence field With phase decoherence

We investigate the time evolution of the entanglement in the interacting system of a single two-level atom and a single mode coherence field with phase decoherence and discuss the influences of the coupling constant of light and atoms,mean photon number of light and detuning.The results show that the oscillating frequency of the entanglement of the system will increase with the increasing of the coupling constant of light and atoms and the mean photon number of light.The influence of the detuning on time evolution of the entanglement is obvious without phase decoherence and the quantum state of the field and atom will stay in a most entangled state for a long time when the detuning is proper.The phase decoherence causes the fading of entanglement when the system is resonant and it will fade to zero at last.The entanglement of the system is a fading oscillation at first with phase decoherence.The detuning restrains the phase decoherence with the time evolution.In this case the entanglement of the system will not fade to zero at last.The oscillating amplitude of the entanglement is lessening at first and the entanglement will quickly become a constant value with the increasing of detuning.The system will stay in an entangled state with phase decoherence if the detuning is proper.