  The capacity of a channel is known to be equivalent to the highest rate at
which it can generate entanglement. Analogous to entanglement, the notion of a
causality measure characterises the temporal aspect of quantum correlations.
Despite holding an equally fundamental role in physics, temporal quantum
correlations have yet to find their operational significance in quantum
communication. Here we uncover a connection between quantum causality and
channel capacity. We show the amount of temporal correlations between two ends
of the noisy quantum channel, as quantified by a causality measure, implies a
general upper bound on its channel capacity. The expression of this new bound
is simpler to evaluate than most previously known bounds. We demonstrate the
utility of this bound by applying it to a class of shifted depolarizing
channels, which results in improvement over previously calculated bounds for
this class of channels.
