中文摘要：

通过求解系统的Milbum方程，研究了内禀退相干下两比特海森伯XY模型中的热纠缠性质．讨论了非均匀磁场、系统初始纠缠度、两比特的相对相位对系统热纠缠的调控作用．结果表明：在系统一定的初始条件下，磁场的引入能够大大提高两比特间的热纠缠程度；在固有退相干存在的情况下，系统热纠缠强烈依赖于两个自旋比特的初始态，通过控制两自旋比特的相对相位和振幅，可以获得系统的稳定热纠缠．结果还表明：在没有外界磁场时，发现Bell正交态是系统的“暗态”，它的热纠缠度在演化过程中不受系统内禀退相干的影响．

英文摘要：

By solving the Milburn equation, we investigate the thermal entanglement properties of a two-qubit Heisenberg XY chain in the presence of intrinsic decoherence. The controls of nonuniform magnetic field, the initial state of two qubits, the relative phases and the amplitudes of the polarized qubits on thermal entanglement are studied. The results show that for a particular initial state, the thermal entanglement can be increased by the external magnetic field. The time behavior of the entanglement exhibits a strong dependence on the initial state of two qubits, and it can be manipulated by changing the relative phase and the amplitudes of the polarized qubits. It is also notable that stable entanglement, which is dependent on initial state of the qubit, occurs even in the presence of decoherence. The magnetic field may have a constructive effect on the stable entanglement for a certain initial state, and the Bell-diagonal state turns out to be a ＂dark＂ state of the system in the absence of the magnetic field.