Characterization of linear maps on $M_n$ whose multiplicity maps have maximal norm, with an application in quantum information

Daniel Puzzuoli

Given a linear map $\Phi :M_n\to M_m$, its multiplicity maps are defined as the family of linear maps $\Phi \otimes {\text{id}}_k:M_n\otimes M_k\to M_m\otimes M_k$, wh…