  A communication protocol with non-zero quantum capacity is found when the two
communicating parts are particle detector models in (3+1)-dimensional
spacetime. In particular, as detectors, we consider two harmonic oscillators
interacting with a scalar field, whose evolution is generalized for whatever
background spacetime and whatever spacetime smearing of the detectors. We then
specialize to Minkowski spacetime and an initial Minkowski vacuum, considering
a rapid interaction between the field and the two detectors, studying the case
where the receiver is static and the sender is moving. The possibility to have
a quantum capacity greater than zero stems from a relative acceleration between
the detectors. Indeed, no reliable quantum communication is possible when the
two detectors are static or moving inertially with respect to each other, but a
reliable quantum communication can be achieved between a uniformly accelerated
sender and an inertial receiver.
