非旋波近似下Λ型三能级原子与相干态光场的量子纠缠  

Quantum Entanglement of the Coherent State Field Interacting with a Λ Type Three-level Atom Without Rotating Wave Approximation

作　　者：夏建平[1] 任学藻[1] 丛红璐[1] 姜道来[1] 廖旭[1] 

机构地区：[1]西南科技大学理学院,四川绵阳621010

出　　处：《光子学报》2010年第9期1621-1626,共6页Acta Photonica Sinica

基　　金：国家自然科学基金委员会-中国工程物理研究院联合基金(10976025/A06)资助

摘　　要：在非旋波近似下,利用相干态正交化展开方法,对相干态光场与Λ型三能级原子相互作用的量子场熵进行了精确求解.利用量子熵理论讨论了耦合强度、平均光子数以及初始时刻原子处于不同的能级对量子纠缠的影响.数值计算的结果表明:当初始时刻原子处于激发态时,量子纠缠在较短的时间内就能演化到最大值,随着平均光子数的增大,纠缠演化的周期性逐渐明显;原子初始时刻处于三个能级的叠加态会使初始阶段量子纠缠显著降低;与旋波近似下的结果不同的是,随着耦合强度以及平均光子数的增加,非旋波项的贡献显著增强,使得量子纠缠演化曲线出现小锯齿状的振荡.Applying the method of coherent-state orthogonalization expansion, the quantum entropy of the coherent state light field interacting with a Λ type three level atom is caculated accurately without rotating wave approximation. The influences of the couplings, mean photon number and the atom in different levels at the initial time on quantum entanglement are studied via quantum entropy theory. The results obtained from using the numerical method show that when atom is initially in the excited state, the entanglement reaches the maximum value in a short time, with the increase of the mean photon number, the period of entanglement evolution becomes clearly. The degrees of enganglement in a short time become lower due to the atom is initially in the superposition state of all three levels. Compared with the results of using the method of rotating wave approximation, the contribution of the without rotating wave approximation terms increase notably and the quantum entanglement curvies displays small zigzag-shaped oscillation, with the increasing of couplings and mean photon number.

关 键 词：量子纠缠 相干态光场 Λ型三能级原子 

分 类 号：O431.2[机械工程—光学工程]