We will call a completely positive map a quantum channel if it preserves the trace, i.e. if Tr [T (X)] = Tr [X] for any X ∈ M d 1 . While quantum channels represent general physical processes in the context of quantum information theory, entanglement breaking quantum channels represent such processes that cannot be used to distribute entanglement, and they are useless for any non-classical communication task [1]. Completely copositive quantum channels represent physical processes which are too noisy to be used for some information processing tasks (e.g. quantum communication [2]). However, unlike entanglement breaking channels they can sometimes be used for certain non-classical information processing tasks (e.g. private communication [3]). * Electronic address: christandl@math.ku.dk † Electronic address: muellerh@posteo.net, muellerh@math.ku.dk ‡ Electronic address: m.wolf@tum.de