Universal upper bound for the Holevo information induced by a quantum operation

Abstract: Let be a bipartite system and a quantum state on , , . Then each quantum operation on the quantum system can induce a quantum ensemble on quantum system . In this Letter, we show that the Holevo quantity of the quantum ensemble can be upper bounded by both subsystem entropies. By using the result, we answer partly a conjecture of Fannes, de Melo, Roga and Życzkowski. [Copyright &y& Elsevier]