Spatial-mode storage in a gradient-echo memory

Abstract

Three-level atomic gradient echo memory ( -GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing [Hosseini et al., Nature (London) 461, 241 (2009)]. In this paper we investigate the spatial multimode properties of a -GEM system. Using a high-speed triggered CCD, we demonstrate the storage of complex spatial modes and images. We also present an in-principle demonstration of spatial multiplexing by showing selective recall of spatial elements of a stored spin wave. Using our measurements, we consider the effect of diffusion within the atomic vapor and investigate its role in spatial decoherence. Our measurements allow us to quantify the spatial distortion due to both diffusion and inhomogeneous control field scattering and compare these to theoretical models.

Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles

“…Applications include remote entanglement via collective Raman scattering in a DLCZ-type protocol [25,26] and for multimode quantum memories [27]. From such studies, it is clear that one-dimensional models not only fail to describe the relevant coherent and incoherent effects, but they also do not take advantage of the resources associated with spatial modes [28,29].…”

Diffusion effects in gradient echo memory

“…According to the formula in Ref. [30], we have D ∼ 0.004 m 2 /s for Rubidium atoms in buffer gas [21,22].…”

“…Typical system parameters are ω 0 = 2π × 377.107 46 THz, ω 0 − ω c = 2π × 6.8 GHz, = −2π × 1.5 GHz, c 2π × 20 MHz, g 2π × 4.5 Hz, t p = 1 μs, a 1.45 mm, 2L = 0.2 m, η −2π × 10 MHz/m, and N 0.5 × 10 18 m −3 [21,22,29]. The optical depth |β| 3.8 is sufficiently large.…”

“…We suggest ways to reduce these effects to improve storage efficiency and also report on a mechanism that explains the discrepancy between the predicted diffusion coefficients based on buffer gas pressure calculation and the echo signal shape, which was seen in Ref. [22]. The effects of diffusion strongly depend on the spatial frequency of the spin wave.…”

“…The spatial multimode properties of a -GEM have been examined experimentally [22]. In this paper, we examine the effects of atomic diffusion on the -GEM system, which may limit this efficiency for larger storage times.…”