Research On The Entanglement Of Atoms In An Optical Cavity Coupled With A Thermal Reservoir

Quantum entanglement is a special and interesting phenomenon in quantum mechanics.It can be used to accomplish tasks that some classical methods cannot accomplish,and plays a significant role in quantum information and quantum computation.However,in practice,the interaction between the quantum system and the external environment is unavoidable,which will cause entanglement characteristics of the system to be destroyed.Therefore,it will be important to study the entanglement characteristics of quantum systems in different environments and to reduce or even avoid the influence of the external environment on entanglement of the system.The model of this thesis is based on three interacting two-level atoms which is in an optical cavity,and the cavity is coupled to a zero-temperature Bose reservoir.We use Laplace transform,LBC and other methods,to study the following two aspects:1.We study the influence of the coupling parameters on excited state population of atom.By studying the evolution of excited state population of atom A,one of the three atom,we discuss the effect of changing the coupling strength between atoms,the coupling strength between atoms and cavity,the spectral width of reservoir,and the detuning of cavity and reservoir on the excited state population of atom A.The study found that the excited state population increases with the increase of the atomic coupling strength,the evolution of excited state population of atom A will be damped oscillation when the the coupling strength is large;as the coupling strength of atom and cavity increases,the excited state population of the atom decreases and exhibits oscillating phenomenon;when the reservoir spectral width is small,affected by the non-Markovian effect,excited state population of atom A with time evolution occurs oscillation,and as the spectral width of reservoir increases,excited state population of atom A also increases;along with the increase of detuning,the excited state population of atom A increases,when the coupling between cavity and reservoir is strong,and the detuning is large,oscillation damping appears.Through numerical calculation,it is found that the evolution of the excited state population tends to a steady value with time.2.We investigate the influence of the coupling parameters on the entanglement evolution of the system.By studying the entanglement evolution of three atoms,entanglement of the cavity and reservoir,and comparing between the two of them,we discuss the influence of changing the coupling strength of atoms,coupling strength between atoms and cavity,spectral width of reservoir and detuning between cavity and reservoir on entanglement evolution and entanglement transfer of subsystems.The results show that in a short period of time,theentanglement between atoms increases with the increase of the coupling strength between atoms and decreases with the increase of the coupling strength between cavity and reservoir;the entanglement between the atoms tends to a stable value in the long time limit;non-Markovian of the system is determined by the spectral width of reservoir and the coupling strength of atom and cavity,when the coupling strength between reservoir and cavity is strong,the system of atoms and cavity is under non-Markovian dynamics,the entanglement of atomic system appears non-Markovian effect,at this time,with the increase of the spectral width of the reservoir,the entanglement of atomic system appears Markovian effect,as the spectral width continues to increase,the system of atom and cavity follows the Markovian dynamics,and the atomic system shows non-Markovian again;by adjusting detuning between cavity and reservoir,we can control the influence of dissipation on entanglement decay effectively.