The Preparation Of Quantum Entanglement Based On NV Center And MTR Resonator Coupling System

In recent years,people have more and more demand for information transmission,and a variety of new media are constantly being produced.The traditional classic communication methods have a series of advantages such as fast transmission speed and wide coverage,and are responsible for most information transmission tasks.With the continuous development of technology,people are beginning to realize that traditional communication methods are not absolutely safe.The society urgently needs a means of information transmission that can be completely confidential.The emergence of quantum information solves this problem.Because of its principle of quantum superposition and quantum non-cloning theorem,the absolute secrecy of information can be achieved by quantum information processing.Quantum information processing is a new subject which integrates physics,computer,communication and so on,which uses the entanglement characteristic of quantum mechanics to make quantum communication by preparing quantum entangled state as the carrier of information propagation,which solves many problems that classical informatics cannot deal with,so it has been widely concerned by scholars at home and abroad.As an indispensable resource for quantum communication and quantum computing,in the field of quantum information processing,entangled states,as the medium and carrier to realize information exchange,carry the key role.It is also because of this that it is very important to study the preparation and mutual transformation of quantum entangled states.At present,according to the physical system used in the preparation,the preparation methods of quantum entangled states are mainly divided into atomic system,optical system,ion trap,cavity quantum electrodynamics and the like.Among them,cavity QED(cavity quantum electrodynamics)has matured in entanglement preparation due to its advantages of high quality factor and small mode volume.The microtoroidal resonator(MTR)is an optical microcavity with high quality factor and small mode volume.The preparation and transformation of quantum entangled states can be carried out by using the longer coherence time characteristics of NV color centers and their coupled systems.Therefore,the coupling system based on NV color center and MTR has many applications in the fields of quantum information processing and quantum key distribution.This article mainly covers the following aspects:This paper first proposes a scheme for preparing entangled states between NV color centers.In this scheme,the NV color center is coupled to the whispering gallery mode(WGM)of the microring resonator(MTR).By utilizing the original polarized photon input and single photon detector measurements,the NV color center will be prepared as an entangled state with the aid of a special input-output process for polarized photons in the MTR.More importantly,both the Bell and W states can be prepared by the optical system proposed by this scheme.This scheme provides physical feasibility for the preparation of entanglement between NV color centers and may pave the way for quantum information processing(QIP)based on NV color centers.Secondly,we also propose a scheme that can transform the W state into the GHZ state.The scheme is based on the CNOT gate of the NV color center and microtoroidal resonator(MTR)coupling system and the cross-Kerr nonlinearities.After theoretical derivation and analysis,this scheme has higher conversion efficiency under the current experimental conditions,which may provide some effective help for the preparation of quantum entangled states.