Realization Of Quantum Beam Splitter For Orbital Angular Momentum Of Light Based On Atomic Ensembles

Light is the ideal carrier of information.Squeezed state and continuousvariable EPR entangled state light fields have incomparable advantages over classical light fields in the fields of high-speed information processing,large-capacity communication,ensuring information security and improving measurement sensitivity.So the generation of squeezed state and entangled state is popular in quantum optics.The frequency of the non-classical light fields based on the four-wave mixing process of atoms can match the atomic transition accurately,which strongly promotes the development of the quantum network of light field as quantum channel and atom as quantum node,and provides guarantee for quantum communication.Orbital angular momentum beams have a special spatial structure,which can form an infinite dimensional Hilbert space.They are widely used in quantum coding,high-dimensional and large-capacity quantum communication.In view of the important application value of orbital angular momentum beams and the unique advantage of generating non-classical optical fields by four-wave mixing,the quantum properties of non-classical optical fields with orbital angular momentum in cesium atomic ensemble based on four-wave mixing process have been studied experimentally.The thesis work includes the following two projects:1.The EPR entangled states with non-zero OAM are experimentally generated in hot cesium vapor based on double-?four-wave mixing process.The Laguerre-Gauss bright twin beams carrying 1 charge were obtained at first.The amplified probe light and the newly generated conjugate light carry the same and opposite topological charges as the seed light,respectively.And the degree of intensity difference squeezed is 6 d B.Then two partite orbital angular momentum continuous-variable entangled states are prepared in this system,and the degree of entanglement is 4 d B.2.The quantum correlation characteristics of four-wave mixing process have been explored in the nonamplifying regime.When the total gain of probe beam and conjugate beam generated in the FWM process is equal to 1,the noise power of the intensity difference of the l=-1 probe beam and the l=+1 conjugate beam is 0.9 d B below the SNL.This FWM device play the role of quantum beam splitter for OAM of light.Based on the advantages of multi-spatital modes of FWM process,this four-wave mixing device will provide a possibility for the quantum beam splitter of image.