采用非旋波近似,讨论了热库中二态量子系统在外加驱动场作用下的退相干性。 利用系统的演化酉算符, 计算出了二态量子系统的约化密度矩阵非对角矩阵元。结果表明:二态量子系统的量子相干性与其初始状态、 热库和外加驱动场的频率、二态量子系统与热库和驱动场的耦合强度等因素有关。确定了外加驱动场与退相干 性之间的关系,并得到了外加驱动场的时间演化满足特定条件时,可保持系统的相干性。

The problem of decoherence of two-state quantum systems interacting with a bath through an external controllable driving field without rotating wave approximation is discussed. The off-diagonal elements of density operator in two-state quantum systems are obtained. The result reflects that decoherence of the two-state quantum systems has something to do with its original state, frequency of the bath and external controllable driving field. The relation between the decoherence and external controllable driving field is studied. Properties of an external controllable driving field are obtained when the two-state quantum systems of coherence is maintained.