Quantum memory in an optical lattice

Arrays of atoms trapped in optical lattices are appealing as storage media for photons, since motional dephasing
of the atoms is eliminated. The regular lattice is also associated with band structure in the dispersion experienced
by incident photons. Here we study the influence of this band structure on the efficiency of quantum memories
based on electromagnetically induced transparency (EIT) and on Raman absorption. We observe a number of
interesting effects, such as both reduced and superluminal group velocities, enhanced atom-photon coupling, and
anomalous transmission. These effects are ultimately deleterious to the memory efficiency, but they are easily
avoided by tuning the optical fields away from the band edges.