原子自发辐射中偶极矩的涨落与最大纠缠态的保持

Fluctuation of dipole moment in spontaneous emission of atom and preserving of the most entangled state

研究了二能级原子与电磁场相互作用体系的自发辐射与量子纠缠态。在原子的自发辐射过程中 ,其偶极矩的期待值总是零 ,但偶极矩的涨落恒等于一个不为零的常量 ,因此原子的自发辐射是由真空起伏导致偶极矩的涨落引起的。Jaynes Cummings模型是产生量子纠缠态的重要体系 ,研究发现 ,原子与场纠缠态的信息熵和纠缠度随时间作周期性的振荡 ,量子态在非纠缠与纠缠态之间变化。更为重要的是 ,在失谐量适当时 。

We study the spontaneous emission and quantum entangled state of the system in which a two level atom interacts with electromagnetic field. The expectation value of atom dipole moment is always zero, but the fluctuation of dipole moment is a constant and not zero during the atomic spontaneous emission. Therefore the spontaneous emission of atoms is caused by the fluctuation of dipole moment that arises from vacuum fluctation. Jaynes Cummings model is an important system to produce quatum entangled state. We find that information entropy and the amount of entanglement oscillate with time evolution periodically. The quantum state changes between unentangled state and entangled state. The quantum state will stay in the most entangled state for a long time when the detuning is proper.