J-C模型中原子的自发辐射与量子纠缠态

SPONTANEOUS EMISSION OF ATOM AND QUANTUM ENTANGLED STATE IN J-C MODEL

通过对旋波近似下J C模型中的二能级原子与单模场相互作用体系的研究 ,得到激发态原子将演化为场和原子的耦合叠加态—纠缠态 .原子偶极矩的期待值总是零 ,但偶极矩的起伏恒等于一个不为零的常数 ,因此 ,原子的自发辐射是由偶极矩的涨落引起的 ,并非原子偶极矩振荡造成的结果 .具体研究这种纠缠态的性质得出 :原子与场纠缠体系的信息熵和纠缠度随时间做周期性的振荡 ,并且和原子与场间的耦合系数及失谐程度有关 ,量子态在非纠缠态与纠缠态之间变化 .在微小失谐量时 。

Through studying the interaction between a two_level atom and a single mode emission field in rotating_wave approximations of Jaynes_Cummings Model, the atom and the field are in a coupled superposition state_entangled state is obtained. The expectation value of atom dipole moment is always zero, but the fluctuation of dipole moment is a constant, but not zero. Therefore it is concluded that the spontaneous emission of atoms is caused by the fluctuation of dipole moment, not by the dipole moment oscillation of the atomic system. The property of the entanglement is also studied and it is obtained that information entropy and the amount of entanglement are oscillating with time_evolution periodically and are related with the coupling coefficient and detuning. The quantum state changes between disentangled state and entangled state. The quantum state will be entangled state for a long time when the detuning is small.