  Quantum memories are essential for quantum information processing and
long-distance quantum communication. The field has recently seen a lot of
progress, and the present focus issue offers a glimpse of these developments,
showing both experimental and theoretical results from many of the leading
groups around the world. On the experimental side, it shows work on cold gases,
warm vapors, rare-earth ion doped crystals and single atoms. On the theoretical
side there are in-depth studies of existing memory protocols, proposals for new
protocols including approaches based on quantum error correction, and proposals
for new applications of quantum storage. Looking forward, we anticipate many
more exciting results in this area.
