The Generation Of Quadripartite Entanglement And The Analysis Of Orbital-Angula-Momentum Mode Based On Four-wave Mixing Process

The non-classical states of light field,such as squeezed state and entangled state,have a wide range of application in quantum computation,quantum network and quantum precision measurement.Therefore,the preparation of multiple beam quantum squeezing and multipartite entanglement is crucial to promote the development of these fields in the continuous variable quantum systems.Recently,our research group has carried out a series of researches on quantum phenomena such as quantum squeezing and quantum entanglement based on the four-wave mixing process in ⁸⁵Rb atomic vapor cell.Based on these works,this paper has carried out further research,and the related research contents are as follows.Firstly,we theoretically propose a scheme to generate genuine quadripartite entanglement by linking two independent four-wave mixing processes with one linear beam splitter.In our scheme,we first construct two independent four-wave mixing processes,and then use one linear beam splitter to connect two probe beams amplified by the four wave mixing process.Based on this,we generate four spatially separated beams.We study the effect of the intensity gains of two independent four-wave mixing processes and the transmissivity of the linear beam splitter on quadripartite entanglement by applying the positivity under partial transposition criterion.After that,in order to reveal the entanglement structure of the system,we also investigate the dependence of possible tripartite entanglement and bipartite entanglement on the intensity gain when the transmissivity of the linear beam splitter remains unchanged.This provides a simple and reliable way for the generation of multipartite entanglement using four-wave mixing process and linear beam splitter.Secondly,we report an experimental implementation of a four-wave mixing process with pump beam of coherent orbital angular momentum superposition mode and seeding probe beam of single orbital angular momentum mode.Here,the mode of the pump beam is the orbital angular momentum superposition mode with topological charges of+1 and-1,and the mode of the probe beam is the orbital angular momentum mode with topological charge of+1.We experimentally study the quantum correlation between twin beams when the pump beams are in different coherent orbital angular momentum superposition modes by changing the intensity of+1 and-1 orbital angular momentum modes in the pump beams.In addition,we study the components of orbital angular momentum mode in each output field,and show the transformation of the nonlinear interaction among different orbital angular momentum modes when the pump beam mode is changed.The obtained results show the rich structure of nonlinear interaction of orbital angular momentum mode in four-wave mixing process and provide a new perspective to study quantum information protocol.