Quantum Memory For Squeezed State Of Light Based On Photon Echoes

Quantum memory for light plays a key role in quantum-information processingand has been considered as a basic ingredient for quantum repeaters and scalableall-optical quantum computers. Nowadays, much effort has been devoted to suchmemories through different approaches, including Faraday rotation,electromagnetically induced transparency, off-resonant Raman transitions, and photonechoes. Photon-echo-based memories are currently attracting particular attention, notonly for the abilities to implement in solid-state materials, but also for the successfulachievement in storage efficiency and multimode-memory capacity. By now, in thisarea, photon echoes have been used to store and retrieve time-bin qubits, entangledphotons, and optical coherent state. However, optical squeezed-state storage based onphoton-echo techniques, as far as we know, has not yet been studied theoretically andexperimentally. Squeezed state of light provides a reduction in one of its quadraturesbelow the standard quantum limit. More specifically, such state has been shown to beespecially valuable for interferometry, high-precision measurement, light-wavecommunications, and quantum information with continuous variables. Therefore,realization of efficient and faithful memory for squeezed state will be very appealing.In his thesis, we start from the basic principle of light-atoms interaction, andderive the equations of motion when take into account the effects of thermal reservoir.Secondly, we detailedly study the quantum memories based on controlled reversibleinhomogeneous broadening (CRIB) and hybrid photon echo re-phasing (HYPER). Under the above investigations, we further describe the main research(1) CRIB-based memory for squeezed state of light. We study the storage andretrieval processes, and show that, for storage process, as long as the optical depth ofthe storage medium is sufficiently large, the quantum features of input optical pulsewill be perfectly preserved even for large degrees of squeezing. However, for retrievalprocess, the reconstructive capacity of the squeezed state also depends on atomicdecay rate. In the case of small decay rate, the quantum memory efficiency can benearly attained100%.(2) Investigating the backward retrieval of squeezed state of light based onHYPER protocol. Such protocol uses natural inhomogeneous broadening lines toimplement quantum memories, which enables us to prepare the storage medium withthe large optical depth. Therefore, as long as the storage medium with the small decayrate is considered, the quantum memory efficiency can be achieved optimally. As aresult, our work opens a practical way for the experimental implmentation of theefficient photon-echo-based memories for squeezed state of light.