用相干态表象论密度矩阵的扩散方程和振幅衰减方程的来源

The source of diffusion equation and amplitude attenuation equation of density matrix by using coherent state representation

光场的扩散和振幅衰减是光场演化的两个主要机制,在量子调控中有重要的应用,也是产生新光场的途径.从物理要求出发来推导密度算符的扩散方程和振幅衰减方程,即从相干态表象来演示这两个方程的经典对应分别是通常意义下扩散方程和振幅衰减方程,这样就可以令人信服地说明它们的合理性.在此基础上证明光场二项式态的振幅衰减即是体现在二项分布的参数的衰减,r_0→r_0e^(-2χt),χ是衰减系数.

Diffusion and amplitude dissipation are two major mechanisms of photon field＇s evolution, which may be used in quantum controlling and in generating new photon fields. Here two time-evolution equations for diffusion and dissipation from the physical point of view were derived, i.e., the coherent state representation was employed to demonstrate that these two equations＇ classical correspondence makes common sense in general. In this way the two equations are reasonable without any doubt. Consequently, it was shown that the dissipation of a binomial state is embodied in its paramenter r0→r0 e -2xt, x is the dissipation coefficient.