Spatial mode storage in a gradient echo memory

TL;DR

This paper explores the spatial multimode capabilities of a lambda-GEM system, demonstrating complex image storage, spatial multiplexing, and analyzing decoherence effects due to diffusion and scattering.

Contribution

It provides the first experimental demonstration of spatial multimode storage and multiplexing in a lambda-GEM quantum memory system, with analysis of spatial decoherence mechanisms.

Findings

Successful storage of complex spatial modes and images

Demonstration of spatial multiplexing via selective recall

Quantification of spatial decoherence effects

Abstract

Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing. In this paper we investigate the spatial multimode properties of a lambda-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 vapour 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.