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

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

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

Hysteresis in the fundamentals of macroeconomics.

Two fundamental problems in economic analysis concern the determination of aggregate output, and the determination of market prices and quantities. The way economic adjustments are made at the micro level suggests that the history of shocks to the economic environment matters. This paper presents tractable approach for introducing hysteresis into models of how aggregate output and market prices and quantities are determined.Hysteresis, Aggregate Output, Market Supply and Demand

Instantaneous processing of "slow light": amplitude-duration control, storage, and splitting

Nonadiabatic change of the control field or of the low-frequency coherence allows for an almost instantaneous change of the signal field propagating in a thick resonant absorber where electromagnetically induced transparency is realized. This finding is applied for the storage and retrieval of the signal, for the creation of a signal copy and separation of this copy from the original pulse without its destruction.Comment: 9 pages, 1 figure, submitted to PRL on 18, December, 200

Electromagnetically induced transparency in an isotopically purified Nd3+^{3+}:YLiF4_4 crystal

We report the first observation of electromagnetically induced transparency (EIT) in an isotopically purified Nd$^{3+}$:YLiF$_4$ crystal. This crystal demonstrates inhomogeneous broadening of optical transitions of about 35 MHz. EIT is observed in a symmetrical $\Lambda$-like system formed by two hyperfine sublevels of the ground state corresponding to a zero first order Zeeman (ZEFOZ) transition and a hyperfine sublevel of the excited state, which is not coupled to other ground-state sublevels. It is found that transmission of the probe field as a function of the two-photon detuning demonstrates a comb-like structure that can be attributed to superhyperfine coupling between Nd$^{3+}$ ions and fluorine nuclei. The observed structure can be resolved only in the vicinity of the ZEFOZ point where the homogeneous linewidth of the spin transition is sufficiently small. The results pave the way for implementing solid-state quantum memories based on off-resonant Raman interaction without spectral tailoring of optical transitions.Comment: PRB, accepte

Quantum storage on subradiant states in an extended atomic ensemble

A scheme for coherent manipulation of collective atomic states is developed such that total subradiant states, in which spontaneous emission is suppressed into all directions due to destructive interference between neighbor atoms, can be created in an extended atomic ensemble. The optimal conditions for creation of such states and suitability of them for quantum storage are discussed. It is shown that in order to achieve the maximum signal-to-noise ratio the shape of a light pulse to be stored and reconstructed using a homogeneously broadened absorbtion line of an atomic system should be a time-reversed regular part of the response function of the system. In the limit of high optical density, such pulses allow one to prepare collective subradiant atomic states with near flat spatial distribution of the atomic excitation in the medium.Comment: V2: considerably revised (title, text). V3: minor changes - final version as published in PR