Research On The Dynamics Of Quantum Coherence And Entanglement Based On Cavity Structure

In this paper,the dynamics properties of quantum systems are researched based on various Cavity structure.The theoretical research is conducted from various aspects,including,single-mode cavity and multi-mode cavity,steady-state cavity and unsteady-state cavity,single-atom and multi-atom,additional cavity or not,two-dimensional atom and three-dimensional atom.The main contents are as follows:(1)The background,significance,the general definition of the state evolution equation of closed system and the degree of entanglement are systematically described.The mathematic processing method used in theoretical derivation is briefly introduced,and the main research content and innovation points of this paper are also introduced.(2)The entanglement dynamic properties of the two-volume subsystem is studied.The two-volume subsystem is from a composite quantum system,which is composed of two independent systems of two-level atom coupling to a single-mode cavity.The dynamics of cavity-cavity and atom-cavity entanglement are numerically analyzed under different initial states and detuning by solving Schr?dinger equation and using concurrence.The results show that the local coupling between atoms and cavity not only induces the local entanglement of atom and cavity,but also induces the non-local entanglement between cavity and the other cavity.The entanglement between cavities compensate for the initial entanglement between atoms exactly at zero detuning.It is also found that the detuning can affect the exact compensation.(3)The entanglement dynamic properties of the two-volume subsystem in a composite system composed of two independent double two-level atoms and a single-mode cavity coupling system are studied.The dynamics of atom-atom and atom-cavity entanglement are numerically analyzed under different conditions of coupling parameters and detuning by solving Schr?dinger equation and using negativity.It is found that the effect of the inter-atomic dipole interaction on the entanglement of the subsystems can be neglected for a certain period of time.The coupling between atom and cavity and the effect of detuning on the entanglement of each subsystem cannot be neglected.In a certain period of time,the average value of entanglement of subsystems increases with the increase of the coupling parameter between atoms.The average value of entanglement of subsystems can be decreased by increasing the coupling parameter between atoms and cavities and the increase of the amount of detuning.Moreover,the increase of the coupling parameter between atoms and cavities and increase the amount of detuning can suppress the entangled oscillation of subsystems.(4)In order to modulate entanglement,a setup is designed which can not only generate entangled state,but also control entanglement via parameter adjustment.In this chapter,a scheme of creation of entangled states is proposed based on a V-type three-level atom and cavity quantum electrodynamics systems.The dynamics of cavity-cavity entanglement is numerically analyzed under different conditions of coupling parameters.It is found that the cavity-cavity entanglement can be mediated by varying the coupling parameters between cavities when the V-type three-level atom successively passes through the two cavities at a constant speed.Moreover,this scheme can be utilized for the simultaneous generation and for controlling of multi-component quantum entanglement.(5)The entanglement dynamic properties of the two-volume subsystem in a composite system composed of an isolated two-level atom and a two-level atom-multimode cavity field coupled system is studied.Considering that there is at most one excitation in the system,the exact evolution state of the system is obtained by using Fourier transform and Laplace transform,and the density matrix of each subsystem in the complex system is obtained by using partial trace,so as to study the evolution rules of the subsystem.In Markov situation and non-Markov situations,the effects of initial correlations on atomic systems and complex systems are discussed.The results show that the effect of initial correlations on the subsystem entanglement is negligible under the Markov effect.Under the non-Markov effect,increasing the initial correlation can suppress the entanglement oscillations of the subsystem and prolong the entanglement decay time.At the same time,it is found that,when the initial correlation takes a certain value,the stable maximum entangled state is obtained,which does not need the atomic pairs that are initially in the maximum entangled state.In a word,this paper studies the entanglement dynamics of a closed quantum system in various cavity structure from multiple perspectives,not only beneficial to entanglement generation and control,but also contributing to the quantum computing and so on.