Quantum memory based on a spatiospectral atomic comb

An atomic comb structure consisting of both spatial and spectral components is proposed for the implementation of quantum memory using inhomogeneously broadened atomic ensembles, such as rare-earth ions trapped in solids. The spatiospectral comb can be prepared in two-level atoms provided a third energy level is available for atomic population storage. The output photon is retrieved from the memory as a spatially diffracted photon echo. The angle between the input and output directions is controlled by the spatial component of the atomic comb. The memory efficiency is analyzed using coupled wave theory, which results in memory efficiency varying with the retrieval angle: 54.1$%$ in collinear, 81.6$%$ in perpendicular, and 100$%$ in counterpropagating configurations. An experimental method for creating a multidimensional atomic comb is suggested.