通过求解系统的Milburn 方程,研究了二项式光场与二能级原子相互作用系统中的场熵演化特性,讨论了内禀退相干、二项式光场系数和场的最大光子数对场熵演化的影响.结果表明二项式光场处于中间态时,由于内禀退相干,场熵振荡准周期性减弱,并随着时间的演化,场与原子纠缠逐渐趋近于一个定值,说明存在內禀退相干时,场与原子仍能纠缠；当內禀退相干因子不变时,二项式光场从相干态过渡到中间态,直至数态过程中,场熵值减小,场与原子的纠缠减弱.

The entropy envolution properties in the system of the binomial optical field interacting with a two-level atom was inverstigated by calculating Milburn equation . The influences of instrinsic decoherece,the parameters η of the binomial optical field and photon number on the entropy evolution were discussed. It is shown that the quasi-periodicity of the entropy vibration will become weak for the intrinsic decoherece .When the binomial optical field is at the middle states,and the entanglement in the field-atom system approaches to a certain value with time evolution. So the entanglement can be kept with intrinsic decoherece. The value of field entropy decreases and the entanglement is weaken for the binomial optical field changing from a coherent state to a middle state then to a fock state as the parameter of intrinsic decoherece is at a fixed value.