Research On Dissipative Preparation Of Entangled Two-atom States In Cavity QED

Quantum information is a particularly important discipline coming from the development of quantum optics.The main directions involved in the field of quantum information are: quantum communications,quantum computing,quantum radar,quantum games and so on.Since the quantum information field is currently developing rapidly,how to effectively prepare quantum entangled states,such as Bell states,W states,and GHZ states,has become a tough and intriguing task for most researchers.As one of the most important quantum entanglement states in quantum information,the Bell states are the main research object and the carrier of the realization of many scientific schemes.In this dissertation,the main content of our research is the design of an dissipation scheme for entanglement in quantum communication.The noise in cavity QED system includes: spontaneous emission of atoms,leakage of cavity modes,and other major dissipative factors.These are factors that researchers need to consider seriously when designing their solutions to problems.Because the scheme of preparing the quantum entanglement states based on the traditional unitary dynamics process cannot avoid the inherent dissipation factors of these systems themselves,the traditional scheme has a low fidelity and the entangled states prepared are easily decoherent due to the environment' impact and other shortcomings.So this traditional method need a further improvement.In this dissertation,we consider how to use the dissipative process to design a theoretical scheme with maximum fidelity based on the fact that two identical three-level atoms of the same ‘shape' can effectively prepare atomic entangled states.The physics principle is that we make the harmful atom's spontaneous radiation and cavity mode leakage favorable factors through the dissipative dynamic process,thereby increasing the maximal value of fidelity effectively.The main contents of this dissertation include: analysis of current research status of the subject at home and abroad,the specific description of interaction between atoms and environment,the generalized model study of dissipative preparation of diatomic entanglement in cavity QED,and the use of a cavity mode and a laser field as the driving force on this model.The study of the dissipative preparation of the Bell state,how the effective operators come from and the analysis of its specific applications,and the dissipative preparation of two Lambda-shaped three-level atoms in the cavity QED.The influence of different parameters' magnitude on the population number and the dynamic change of photon number are analyzed for these two schemes.The Bell states,which are atomic entangled states generally prepared by a dissipative dynamical process,has the advantages of a high fidelity,a shorter preparation time,and robotness against environment.And the schemes proposed in this dissertation can be realized in the actual experiments.When the parameters in the scheme come from the current experiments,the given fidelity can still obtain a relatively high value.This scheme provides a new and fundamentally different idea on how to create entangled states effectively in the field of quantum information.Due to the simplicity of the program,it is also suitable for practical operations(such as cold atomic systems,solid state quantum devices).