Study On Application Of Photon Echo In The Quantum Repeater

Quantum communication can be used to accomplish the task which the classical communication could not complete by quantum properties.With the advantage of large communication capacity,transmission speed and absolute safety,quantum communication provides more secure transmission mode and wider range of applications for communication system.On the realization of long-distance quantum communication,this paper discusses the core elements of quantum repeaters from the two aspects of the quantum memory and entanglement.Photon echo technology has received extensive attention for its efficient storage and multimode storage in solid materials,except for the application in memory,it also can be used to generate entanglement and swap entanglement.Based on the basic principle of interaction between light and atoms,the Maxwell-Bloch equation is established by the quantum theory.In order to complete these storage schemes,in the second chapter,the rare earth ions in solid materials,inhomogeneous broadening,interaction between light and matter,and spectral burning hole technology are introduced.The main contents of this paper can be summarized as follows.First,this paper introduces the main storage schemes currently based on photon-echoes: controlled inverse inhomogeneous broadening(CRIB),atomic frequency comb(AFC),gradient echo memory(GEM)and hybrid photon-echo rephrasing(HYPER).In these schemes,CRIB?AFC andGEM all require the inhomogeneous broadening line through spectral hole burning,however the spectral hole burning do not only waste the effective optical depth,restrict the choice range of storage materials,but has many difficulties in the actual operation.In order to avoid the use of spectral hole burning technology,the HYPER scheme is proposed.In addition to the different conditions for these storage schemes,their storage efficiency are not the same.This paper discusses the evolution equation of each program and calculates the storage efficiency of each scheme in detail.Secondly,a scheme to generate three-body entanglement of light using photon echo technology is presented.By injecting a classical electromagnet field into a crystal doped with rare earth ions placed in free space,three-body entanglement of light pulse can be created when the atomic system rephrased.Finally,based on the characteristics of the scheme,we find it has the potential application in the improving of the efficiency of quantum repeater.