Entanglement Protection Of Two-qubit In Non-makovain Environment

Quantum entanglement is an important resource and plays an important role in quantum information processing.However,the interaction between the quantum system and the environment leads to decoherence,which leads to quantum entanglement loss and even sudden death.In a non-Markovian environment,the phenomenon of backflow and oscillation occurs in quantum entanglement,and the memory effect of non-Markovian environment can be used to protect the entanglement of the system.In this paper,we investigate the quantum entanglement of the system of two-level atom that interacts with their independent reservoir by weak measurement and weak measurement reversal in a non-Markovian environment of amplitude damping channel.The main contents of this paper are as follows:The first chapter introduces the research background and significance,and introduces the quantum information theory.In the second chapter,the theory of quantum entanglement and its quantification are introduced,and here is a briefly introduction of quantum Fisher information.In the third chapter,we introduce the dynamical process of open quantum systems,introduce quantum noise channels such as amplitude damping channel,and introduce the characteristics of quantum entanglement and quantum Fisher information in nonMarkovian environment.In Markovian environment,entanglement and quantum Fisher information decrease monotonically;in non-Markovian environment,entanglement and quantum Fisher information appear oscillation phenomenon.In the fourth chapter,the basic theory of weak measurement and weak measurement reversal is introduced.Based on weak measurement and weak measurement reversal,we present two schemes of entanglement protection.The scheme 1 is to control the entanglement by using pre weak measurement and post weak measurement reversal.Scheme 2 operates with twice weak measurement.After the comparison of the two schemes,the optimal scheme(scheme 1)is adopted to control the entanglement in the non-Markovian environment.The results showed that,in the non-Markovian environment,quantum entanglement interacts with the environment after pre weak measurement,which reduce the influence of decoherence to quantum systems.Quantum entanglement is restored by post-weak measurement reversal,and then achieve the protection of entanglement.The fifth chapter is the summary and outlook of the full paper.