Study On Storage Efficiency Of Optical Quantum State Based On Photon-echo Technology

Light is a very good carrier of quantum information, but photons are difficult tostore for a long time. During the past decade, the optical quantum memories havebecome one of the active areas of research in the field of quantum information. Inquantum communication, the construction of quantum communication networkdepends on the quantum repeater, while one of the core technologies of quantumrepeater is optical quantum memory; in linear optics quantum computation, the opticalquantum memory is the essential elements of information exchange, storage, andprocessing. Important progress has been made in the optical quantum memory basedon the nonresonant Raman transitions, electromagnetically induced transparency, andphoton echo quantum memory techniques. Photon echo quantum memory techniquesare currently attracting particular attention due to solid-state-based implementationand their multimode storage capacity. High efficiency is essential elements forpractical quantum information applications. In this paper, our study concentrates onthe quantum memory efficiency of photon echo techniques.This thesis first Started from the basic principle of light-atoms interaction. Weparticularly deduced the evolution of light field and atoms field. And then, wecarefully studied the photon echo controlled reversible inhomogeneous broadening(CRIB) scheme and hybrid photon-echo rephasing (HYPER) scheme. Based on theseschemes, we further described the main research content of this paper;(1) The improvement scheme of photon echo CRIB technique. The theoreticalcalculation was applied to the process of the photon echo CRIB technology. We foundthat100%efficiency occurred only for extremely large optical depth. However, highoptical depth is very difficult to achieve in practice, especially for the attractivesolid-state systems, such as Rare-earth ion doped crystals. Therefore, the storageefficiency is very low in experiment. In order to increase the efficiency we improvethe original CRIB protocol. We investigated the implementation of CRIB technique inan optical cavity. From calculation we obtained that either a forward or a backwardretrieval process the quantum memory efficiency could reach unity even for a smalloptical depth.(2) The improvement plan of photon echo HYPER technique. In comparisonwith the CRIB protocol，the HYPER technique does not rely on spectral holeburningby the use of the initial natural inhomogeneous profile atomic system，which makes ushave the potential implementation in a large range of systems. From the detailtheoretical calculation, we found that the efficiency can be equal to unity for largeoptical depth in this scheme. Then,，we studied this scheme in an asymmetric optical cavity. In the condition of impedance matching to an optical cavity, we found that theinput light pulse could be completely absorbed by an atomic ensemble. And thequantum memory efficiency can be equal to unity even for a small optical depth of theatomic system. Therefore, our improvement proposal offered promising possibilitiesfor the practical realization of high quantum memory efficiency.