Quantum Entanglement Based On Entropy In Composite Systems

Quantum entanglement,the most essential resource in quantum mechanics,has got a wide spread extensively used in quantum information processing.As well known as,von Neumann entropy is the theoretical basis and mathematical tool of quantum entanglement discrimination and entanglement degree characterization.Therefore,in order to study quantum entanglement,it has certain theoretical value and practical significance to use von Neumann entropy.In this paper,we studied the relationship between entanglement and entropy in composite quantum systems.The main contents are as follows:1.Using the von Neumann entropy,the relation between entanglement and parameter of entangled state was analyzed.Based on the cluster state to realize the invisible transmission of the two-particle entangled state,firstly,we analyzed the relationship between the entanglement change of the entangled state and the parameters before the transmission.Secondly,we studied the relationship between the entanglement degree of the collapsed state and the parameters of the transmitted entangled state and the channel parameters.Finally,the reasonable range of channel parameters was obtained by the entanglement degree and success probability.2.The relationship between quantum measurement and system,information gain and entanglement were studied,respectively.Firstly,the purification system was introduced,and the noise caused by quantum measurement was modeled as the tripartite quantum systems.Secondly,the relationship between information gain and coherent information,system disturbance was discussed respectively.Finally,the relationship between information gain and entanglement was obtained in this tripartite quantum systems.