MiS Preprint Repository

The coherence-breaking channels play a significant role in quantum information theory. We study the coherence-breaking channels for qubit systems and give a method to amend the coherence-breaking channels by applying unitary operations. For given incoherent channel $\mathrm{\Phi }$, we give a necessary and sufficient condition for the channel to be a coherence-breaking channel and amend it via unitary operations. For incoherent channels $\mathrm{\Phi }$ that are not coherence-breaking ones, we consider $\mathrm{\Phi }\circ \mathrm{\Phi }$ and give the conditions for coherence-breaking and channel amendment as well.