On the Alberti-Uhlmann Condition for Unital Channels

Abstract

We address the problem of existence of completely positive trace preserving (CPTP) maps between two sets of density matrices. We refine the result of Alberti and Uhlmann and derive a necessary and sufficient condition for the existence of a unital channel between two pairs of qubit states which ultimately boils down to three simple inequalities.

arXiv commentcomments welcome

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Cited by in corpus (1)

• Interpolating between positive and completely positive maps: a new hierarchy of entangled states