Amending Coherence-Breaking Channels via Unitary Operations

Abstract

The coherence-breaking channels play a significant role in quantum information theory. We study the coherence-breaking channels and give a method to amend the coherence-breaking channels by applying unitary operations. For given incoherent channel Φ, we give necessary and sufficient conditions for the channel to be a coherence-breaking channel and amend it via unitary operations. For qubit incoherent channels Φ that are not coherence-breaking ones, we consider the mapping Φ ∘Φ and present the conditions for coherence-breaking and channel amendment as well.