  Information theory is a statistical theory concerned with the relative state
of detectors and physical systems. As a consequence, the classical framework of
Shannon needs to be extended to deal with quantum detectors, possibly moving at
relativistic speeds, conceivably within curved space-time. Considerable
progress toward such a theory has been achieved in the last ten years, while
much is still not understood. This review recapitulates some milestones along
this road, and speculates about future ones.
