Coherent communication of classical messages

Area of Science:

• Quantum Information Theory
• Quantum Communication

Background:

• Coherent communication is a fundamental concept in quantum information theory.
• Understanding its relationship with other quantum resources is crucial for advancing quantum technologies.

Purpose of the Study:

• To define coherent communication using a simple primitive.
• To establish its equivalence with sending classical messages via unitary or isometric operations.
• To generalize superdense coding and derive formulas for quantum capacities.

Main Methods:

• Definition of coherent communication.
• Relating coherent communication to unitary and isometric operations.
• Generalization of superdense coding.
• Derivation of single-letter formulas for capacities.

Main Results:

• Coherent communication is defined and shown equivalent to classical messaging via quantum operations.
• Superdense coding is generalized to prepare arbitrary quantum states.
• Single-letter formulas for classical and quantum capacities are derived for bipartite unitary gates with entanglement.

Conclusions:

• Coherent communication serves as a unifying resource in quantum information theory.
• The generalized superdense coding has implications for quantum state preparation.
• The derived capacity formulas offer insights into the power of entanglement-assisted quantum channels.