Paper detail

Quantum-correlation breaking channels, broadcasting scenarios, and finite Markov chains

One of the classical results concerning quantum channels is the characterization of entanglement-breaking channels [M. Horodecki et al., Rev. Math. Phys 15, 629 (2003)]. We address the question whether there exists a similar characterization on the level of quantum correlations which may go beyond entanglement. The answer is fully affirmative in the case of breaking quantum correlations down to the, so called, CQ (Classical-Quantum) type, and the corresponding channels turn out to be measurement maps, while it is no longer true in the CC (Classical-Classical) case. The study of the latter reveals an unexpected link between quantum state and local correlation broadcasting and finite Markov chains. We present a possibility of broadcasting via non von Neumann measurements, which relies on the Perron-Frobenius Theorem. Surprisingly, this is not the typical generalized C-NOT gate scenario, appearing naturally in this context.