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On decomposability of positive maps between $M_2$ and $M_n$

Wladyslaw A. Majewski·Marcin Marciniak
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Abstract

A map $ϕ:M_m(\bC)\to M_n(\bC)$ is decomposable if it is of the form $ϕ=ϕ_1+ϕ_2$ where $ϕ_1$ is a CP map while $ϕ_2$ is a co-CP map. A partial characterization of decomposability for maps $ϕ: M_2(\bC) \to M_3(\bC)$ is given.

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Wladyslaw A. Majewski, Marcin Marciniak. 2005-10-07. On decomposability of positive maps between $M_2$ and $M_n$. https://arxiv.org/abs/math/0510138

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