Research On Measurement Of Entanglement Concurrence And Quantum Network Coding

With the rapid development of quantum information technology,quantum entanglement is found to be an important physical resource.Whether it is quantum communication or quantum computation,quantum entangled states are widely used.Quantum entanglement can be divided into many types.For example,in discrete variable systems,the typical entanglement is the two-photon polarization entanglement.If the quantum state can simultaneously entangle in multiple degrees of freedom,such an entangled state is called a hyperentangled state,such as polarization-spatial mode hyperentangled state and polarization-path hyperentangled state.Recently,another kind of entanglement,called hybrid entanglement,has also been used in quantum information processing.However,it is usually difficult to directly characterize entanglement.Therefore,it is very important to measure the entanglement of quantum entangled states,and it has practical application value.With the deepening of the research on quantum communication and quantum computation,scientific researchers have proposed the concept of quantum communication networks.However,there is a bottleneck problem when transmitting quantum information on the public channel in the quantum communication network.Therefore,effective quantum network coding to solve the bottleneck problem has become a hot issue in research.This paper focuses on two aspects: direct measurement of entanglement concurrence and quantum network coding.Firstly,by studying and studying the existing direct measurement schemes of entanglement concurrency,we propose a direct measurement scheme of mixed entanglement states concurrency.This scheme only uses polarization beam splitters,beam splitters,and crossed Kerr nonlinear media.This is entirely feasible in future experiments,and the protocol may be beneficial to future quantum information processing.In addition,through the study of quantum network coding,we give a butterfly quantum network coding scheme based on super entangled Bell states.The advantage of this scheme is that not only the transmission rate of quantum information in the quantum network has been significantly improved,but also the number of entangled photons can be saved,and the Bell state measurement at different degrees of freedom will not destroy the entanglement of another degree of freedom.This protocol may have broad application prospects in the future quantum communication field.