Generalizing Choi map in M3 beyond circulant scenario
We present a generalization of the family of linear positive maps in M3 proposed thirty years ago by Cho et al. (Linear Algebra Appl. 171, 213 (1992)) as a generalization of the seminal Choi non-decomposable map. The necessary and sufficient conditions for decomposability are provided.
On decomposability of positive maps between M2 and Mn
A map $ϕ:M_m(\bC)\to M_n(\bC)$ is decomposable if it is of the form ϕ=ϕ1+ϕ2 where ϕ1 is a CP map while ϕ2 is a co-CP map. A partial characterization of decomposability for maps $ϕ: M_2(\bC) \to M_3(\bC)$ is given.
A Class of Extremal Positive Maps in 3×3 Matrix Algebras