We are studying the communication capacities of unitary two-party unitary quantum interactions. We have found expressions for their one-way classical and quantum capacities assisted by an arbitrary amount of entanglement per use of the gate. More importantly, classical communication using unitary methods has turned out to be a useful abstraction for studying other problems in quantum information theory. This abstraction, called "coherent classical communication," has led to short proofs of many of the central results in the field, and allowed the unification of several problems in quantum information theory.