Experimental Study Of Noise Filtering For Quantum Storage

Quantum communication as a new type of unconditionally secure information transmission network has been closely watched.But the photons carried by quantum bit also suffer the influence of classical and quantum noise in the course of channel transmission,this will cause the decoherence of quantum bits,the phenomena of resulting in loss of information.In order to realize quantum signal transmission distances stable,H.J.Briegel first put forward the theoretical scheme of quantum repeater in1998,and during the next few years,has carried on the further changes and development.At present,the program has become the forefront of research hotspot.Quantum repeater mainly includes entanglement preparation,quantum storage,entanglement passivation and entanglement swapping.Quantum storage is the basis of entanglement generation.Cold atomic ensemble with collective excitation nonlinear enhancement effect and longer spin wave coherent elimination time,can significantly improve memory storage life of atom.Now,storage scheme based on cold atomic medium.have two ways,which is commonly used in the current international.That is EIT dynamic process and Raman scattering process.Because there are a multiple zeeman atomic energy level,In the process of the two above will also generate magnetic sensitive spin wave and magnetic insensitive spin wave.Among them,we need to eliminate the rapid decoherence of magnetic sensitive spin wave to influence of the quantum memory.Therefore,It has player a key role on the filtering noise reduction for success or failure of the whole experiment,and it is also necessary to establish a tangled conditions.This paper revolves around the multiple level atom with coherent light field mechanism of action,we conducted multiple quantum storage and noise filtering experiment research,it mainly includes the following two parts:First,we introduced the EIT dynamic process and spontaneous ramanscattering process.Based on this,we carry out experimental study of the quantum storage and routing distribution,and analyze magnetic sensitive spin wave(noise)on the influence of the fidelity of quantum storage life and the system process.Second,we studied two kinds of narrow-band filtering scheme,which is used to suppress the magnetic sensitive wave impact on quantum storage.(1)Around for atomic ensemble in the research of quantum filtering system in storage,we first briefly introduced the basic principle of F-P etalon and related knowledge,and emphatically analyzes the influence of non-parallel F-P etalon on transmission bandwidth and rate.finally,we design the F-P etalon filter and its performance measurement and analysis.(2)In order to make up for some inherent defects of F-P etalon,we followed by the design of different kinds of optical filter cavity.Theory for calculating the cavity mode laser with filter matching conditions.At the same time,according to the experimental space layout,we improve the structure of the filter cavity,the design for four mirror Z type cavity and five mirror folded cavity.