基于两个子系统的复合体系的纠缠度可以用复合体系密度矩阵的部分转置矩阵负本征值来定义的特性，利用数值模拟方法研究了与单模粒子数场进行相互作用的Tavis－Cummings模型中两原子的纠缠的时间演化。当考虑两原子初始处于混态时，结果表明，粒子数场的初始态、两原子的初始态以及两原子与粒子数光场的耦合常数的大小都对两个原子间纠缠度的时间演化特性有着显著的影响。

Based on the entanglement degree of two subsystem which can be measured by the negative eigenvalues of the partial transposition matrix,time evolution of entanglement degree of two atoms in the Tavis-Cummings model,which is interacted with a field in the Fock state,is investigated by numerical methods. When these two atoms are initially prepared in mixed states,the results show that the field in the Fock state,the initial state of two-atom and the coupling constant between the field and the two-atoms have a dramatic influence on the time evolution character of entanglement degree of two atoms.