类W态原子与耦合腔相互作用系统中的纠缠动力学

Entanglement dynamics in the system of W-like states atoms interacting with coupled cavities

采用Negativity熵度量两体纠缠,通过数值计算研究了类W态原子与耦合腔相互作用系统中两原子间的纠缠。讨论了描述原子初态的参量变化和腔场间耦合系数对两体纠缠的影响。考虑对腔外原子进行选择性测量,通过比较测量前后腔内原子间的纠缠,研究了原子态选择性测量对纠缠的影响。研究结果表明:随囚禁在耦合腔中的两原子间初始纠缠度增大,腔中的两原子间纠缠增强;随腔场间耦合强度的增强,原子间纠缠也增强。另一方面,对腔外原子进行选择性测量,可提高腔内原子间的纠缠。

In this paper,we consider the situation that two of three identical two-level atoms are trapped in two coupled cavities separately and another atom is outside the cavity. The evolution of the state vector of the system is given. Three atoms are in like-W state, and optical cavities are all in vacuum state initially. Negativity is adopted to quantify the degree of entanglement. By means of the numerical calculations, we investigate the temporal evolutions of the entanglement between atoms. The influences of coupling constant between cavities and the parameter describing the atomic initial state on the entanglements are discussed. The results show that the disentanglement time zone of atom-atom entanglement is reduced,and the curve peaks of entanglements increase as initial entanglement between atoms increases. This indicates that the entanglement between atoms is strengthened with the increase of initial entanglement between atoms. The atom-atom entanglement is also strengthened with the increase of the coupling constant between cavities. On the other hand, we consider the case which the state of atom outside cavity is measured. When a direct selective measurement is performed or not, the effect of the state-selective measurement on the entanglement is discussed. We find that the entanglement between atoms can be strengthened through the state-selective measurement.