费米环境中两个三能级原子系统的纠缠演化

利用负性纠缠度(negativity)研究了两个三能级原子系统在费米环境中的纠缠演化问题-结果表明，两个三能级原子系统的纠缠演化不仅依赖于系统和环境的相互作用强度，而且还依赖于系统所处的具体量子态-通过例子发现，系统和环境相互作用强度越大，纠缠衰减越快；对于纯态，仅当时间趋于无穷时纠缠才被完全破坏；对于混态，则在有限的时间内纠缠即被彻底破坏-通过一般的分析找到了一类免退相干的量子子空间-在这些子空间中，量子态不受环境的影响，故其纠缠不变-研究有助于理解费米环境造成的退相干对玻色系统纠缠的影响-关键词：费米环境纠缠演化两个三能级原子

Entanglement evolution of two three-level atoms in a fermionic environment

We study the entanglement evolution of two three-level atoms in a fermionic environment. Our results show that the entanglement evolution depends not only on the strength of the interaction between the system and environment， but also on the structure of states. For the cases of concern， we find that the stronger the interaction between the system and environment is， the faster the entanglement of the system decreases. The entanglement of pure quantum states vanishes completely when the time goes to infinity; while for the mixed state，the entanglement will be completely destroyed by decoherence in finite time. The decoherence-free subspace S_DF has been identified by using linear entropy to measure decoherence. A density matrix that only can be expanded by the elements of S_DF does not perceive the presence of the environment and the entanglement and its linear entropy remain unchangeable. Our analysis will shed some light on the effect of a fermionic environment on the entanglement of bosonic systems.