电荷量子比特与量子化光场之间的纠缠

研究了初态为混合态的电荷量子比特与量子化光场之间的纠缠.通过求解系统的concurrence下限, 研究初态的混合度λ和失谐量Δ对系统纠缠随时间演化的影响. 在弱场中, 电荷量子比特初始是激发态的系统, 其纠缠度远远大于电荷量子比特初始是基态的系统, 并且Δ对系统的纠缠有明显的抑制作用. 在强场中, 电荷量子比特初始分别为激发态和基态时系统的纠缠演化接近一致, 初态混合度最高时系统的纠缠度最小, 并且Δ对系统纠缠的影响变弱.关键词：约瑟夫森结纠缠混合态concurrence下限

Entanglement between charge qubit and quantized field

We investigate time evolution of the entanglement between charge qubit initially in mixed states and quantized field. By calculating the concurrence lower bound, we study the effect of initial mixedness λ and detuning Δ on the entanglement of the system. In the case of weak field, the degree of entanglement for charge qubit being initially in excited state is much larger than that for charge qubit being initially in ground state, and detuning Δ can efficiently reduce the entanglement. But in the case of strong field, the time evolution of the entanglement is about the same for charge qubit being initially in excited and ground states, the more mixed the initial state of charge qubit is prepared, the weaker the entanglement is, and Δ has less effect on the entanglement than in the case of weak field.