Evolution Of Atom Entropy And Population In A Moving Cascade Three-level Atom In A Two-photon Process

In this thesis,we mainly discuss both the entropy evolution properties of field (atom)and the population properties in a moving cascade three-level atom interacting with a single filed through two-photon transitions.Firstly,we introduced the Jaynes-Cummings model and the establishment of the Quantum Optics.Then,the importance and limitations about J-Care described.The introduction of entropy as a means in treating atom-field system is followed.In the second part the theories of entropy about phoenix-knight are introduced ,the currently study status quo on it are also investigated.Then,the resolved method of induced density matrix of entropy in a moving J-C model through a two-photon process are given,so it is provided a theory base on the approach treatment for what we will discuss.In the first section of Chapter3.we simply introduce several conception about quantum entropy;then,some applications and the currently study status of the entropy in(?)type three-level atom are given.In the second section,Under the rotatingwaves approximation and dipole-dipole approximation,we calculate the wave function of the interacting system which a moving cascade three-level atom interacting with a single filed through two-photon transitions by using of full quantum theory.In the third section,By use of the theory of P-Kentropy,in virtue of the deduced wave function,we have discussed the influence of the atomic motion,the field-mode structure parameter and the initial average photon number on the evolution of the entropy,when the atom is initially in coherent state.The results show that the entropy evolution period of the field is dependent of the atomic motion and the field-mode structure parameter.However,the parameter of the initial average photon number will neither lengthen nor shorten the entropy evolution period of the field,but the numerical values of maximum and subminimum of entropy will be affected by it.In the Chapter4,under the same condition,also in virtue of the deduced wave function,we have studied the population properties of the atom.The results show that the rabi oscillation of periodically collapsed and revival of the atom population is relevant of the atomic motion,the field-mode structure parameter and the initial average photon number.the larger the parameter of the initial average photon number,the higher frequency of the rabi oscillation.Just like,the smaller the field-mode structure parameter,the higher frequency of the rabi oscillation.However,the period of the atom population only depends on the field-mode structure parameter.the larger of it,the longer period.but,the initial average photon number will neither lengthen nor shorten the period of the atom population.