Elements of information theory
Elements of information theory
Quantum computation and quantum information
Quantum computation and quantum information
Applications of coherent classical communication and the schur transform to quantum information theory
Quantum Information & Computation
Entanglement-assisted capacity of a quantum channel and the reverse Shannon theorem
IEEE Transactions on Information Theory
On the capacities of bipartite Hamiltonians and unitary gates
IEEE Transactions on Information Theory
Time reversal and exchange symmetries of unitary gate capacities
IEEE Transactions on Information Theory
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A unitary interaction coupling two parties enables quantum or classical communication in both the forward and backward directions. Each communication capacity can be thought of as a tradeoff between the achievable rates of specific types of forward and backward communication. Our first result shows that for any bipartite unitary gate, bidirectional coherent classical communication is no more difficult than bidirectional classical communication -- they have the same achievable rate regions. Previously this result was known only for the unidirectional capacities (i.e., the boundaries of the tradeoff). We then relate the tradeoff for two-way coherent communication to the tradeoff for two-way quantum communication and the tradeoff for coherent communication in one direction and quantum communication in the other.