No-signaling bound on quantum state discrimination

Quantum correlations do not allow signaling, and any operation which may be performed on one system of an entangled pair cannot be detected by measurement of the other system alone. This no-signaling condition limits allowed operations and, in the context of quantum communication, may be used to put bounds on quantum state discrimination. We find that the natural figure of merit to consider is the confidence in identifying a state, which is optimized by the maximum confidence strategy. We show that this strategy may be derived from the no-signaling condition, and demonstrate the relationship between maximum confidence measurements and entanglement concentration.