双模SU(2)相干场与Λ型三能级原子耦合系统中场熵的演化

Evolution of the Entropy of the Field in a System of Λ-type Three-level Atom Interacting with Two-mode SU(2) Coherent field

研究了双模SU(2)相干场与Λ型三能级原子相互作用系统中场熵的演化特性。讨论了两场模与原子的耦合系数相对大小、单模场中光子数的最大可能值N和描述两个场模光子平均数之比参数ξ的变化对场熵演化的影响。数值计算结果表明:两场模与原子的耦合强度近似相等时,场熵随时间作等幅周期性振荡;当两场模与原子的耦合系数相差较大时场熵演化出现崩塌和恢复现象,崩塌持续时间随两场模与原子的耦合系数之比l和两个场模光子平均数之比ξ增大而缩短,随单模场中光子数的最大可能值N增大而增大。

Evolution of the entropy of the field in a system of A-type three-level atom interacting with twomode SU （2） coherent field is studied. The influences of atom-field coulping strengths, the maximum possible number of photons in both modes N and a complex parameter related to the partition of photons in the SU （2） coherent state field modes ξ on evolution of the entropy of the field are discussed. The results obtained using the numerical method show that when atom-field coulping strengths gl and g2 are near entropy of the field displays periodic oscillation; when the difference between atom-fi equel, evolution of the eld coulping strength gl and g2 is obvious, evolution of the entropy of the field displays collapse and revival phenomena. On the other hand, the times of collapses increases with the increase of the maximum possible number of photons in both modes N and with the decrease of the ratio between atom-field coulping strength of two single-mode 1 and a complex parameter related to the partition of photons in the SU （2） coherent state field modes ξ.