Theoretical Study Of Fidelity In Adiabatic Evolution

The research content of quantum open system is a hot topic in modern physics,especially in quantum informatics.In practice,the system we study will inevitably be affected by the external environment and can not be ignored,so the quantum open system has been one of the topics that people pay attention to.The dynamic destruction of quantum coherence caused by the external environment,that is,decoherence,is also a popular research topic in quantum science.In order to suppress the influence of decoherence,a model of decoherence-free subspace is proposed.On the other hand,the adiabatic theorem is the important principle of quantum theory.Quantum adiabatic theorem has been widely used in physical chemistry,quantum field theory and NP-complete problems.The latest development of quantum information processing also makes quantum adiabatic dynamics active again.In this paper,we will investigate the affect of the preparation of steady state in adiabatic evolution of decoherence-free subspaces.The first chapter of the paper introduces the historical development of quantum informatics,the latest frontier development,qubits and the very important principle of superposition in quantum informatics,the development and importance of quantum open systems,and introduces the main idea of decoherence-free subspace.The second chapter mainly introduces the research methods of this paper.The first section introduces the dynamic equation used to analyze the quantum open system,namely the quantum master equation,and the Lindblad master equation under the Markov approximation.The second section introduces the quantum adiabatic theorem and adiabatic conditions.The third section introduces the definition of fidelity and related physical properties.In Chapter 3,we first extend the adiabatic theorem to quantum open systems,introduces the adiabatic evolution of decoherent-free subspaces and the adiabatic conditions of linblad operators.Then,taking a two-level system as an example,we study the preparation of steady state of the system in three quantum processes: Adiabatic evolution of Decoherence-Free Subspaces(ADFSs),Dissipated Engineering Subspace(DES)and Adiabatic Evolution Subspace(AES),The results show that the decoherence-free subspace plays a more active role in the preparation of steady state.Finally,in chapter 4,summarize the research content of the paper.