Multimode cavity-assisted quantum storage via continuous phase matching control

A scheme for spatial multimode quantum memory is developed such that spatial-temporal structure of a weak signal pulse can be stored and recalled via cavity-assisted off-resonant Raman interaction with a strong angular-modulated control field in an extended $\Lambda$-type atomic ensemble. It is shown that effective multimode storage is possible when the Raman coherence spatial grating involves wave vectors with different longitudinal components relative to the paraxial signal field. The possibilities of implementing the scheme in the solid-state materials are discussed.Comment: 8 pages, 3 figures; v2: minor changes, final version as published in PR

Quantum storage based on the control field angular scanning

Continuous change of the propagation direction of a classical control field in the process of its off-resonant Raman interaction with a weak signal field in a three-level atomic medium is suggested for quantum storage of a single-photon wave packet. It is shown that due to phase matching condition such an angular control allows one to reversibly map the single-photon wave packet to the Raman spatial coherence grating. Thus, quantum storage and retrieval can be realized without using inhomogeneous broadening of the atomic transitions or manipulating the amplitude of the control field. Under some conditions the proposed scheme proves to be mathematically analogous to the quantum storage scheme based on controlled reversible inhomogeneous broadening of the atomic states.Comment: 9 pages, 4 figure

All optical quantum storage based on spatial chirp of the control field

We suggest an all-optical quantum memory scheme which is based on the off-resonant Raman interaction of a signal quantum field and a strong control field in a three-level atomic medium in the case, when the control field has a spatially varying frequency across the beam, called a spatial chirp. We show that the effect of such a spatial chirp is analogous to the effect of a controllable reversible inhomogeneous broadening (CRIB) of the atomic transition used in the gradient echo memory (GEM) scheme. However, the proposed scheme does not require temporal modulation of the control field or the atomic levels, and can be realized without additional electric or magnetic fields. It means that materials demonstrating neither linear Stark nor Zeeman effects can be used and/or materials which are placed in specific external fields remain undisturbed

Quantum storage via refractive index control

Off-resonant Raman interaction of a single-photon wave packet and a classical control field in an atomic medium with controlled refractive index is investigated. It is shown that a continuous change of refractive index during the interaction leads to the mapping of a single photon state to a superposition of atomic collective excitations (spin waves) with different wave vectors and visa versa. The suitability of refractive index control for developing multichannel quantum memories is discussed and possible schemes of implementation are considered.Comment: 6 pages, 2 figure

Experimental superradiance and slow light effects for quantum memories

The effects of high optical depth phenomena, such as superradiance, are investigated in potential quantum memory materials. The results may have relevance for several schemes, including CRIB, AFC and EIT-based quantum memories, which are based on using ensembles as storage media. It is shown that strong superradiant effects, manifested as decay rates larger than 1/T2*, are present even for moderate values of alphaL < 5, and increases as a function of alphaL. For even higher alphaL, effects like off-resonant slow light is demonstrated and discussed, and finally, the efficiency of time-reversed optimized input pulses are tested. A maximum retrieval efficiency of ~20% is reached, and agreement with the theoretically expected result is discussed.Comment: RevTeX, 7 pages, 5 figure