Extremal Positive Maps

Decomposable of positive map from M3(C) to M2(M2(C))

“…Woronowicz [11], Theorem 3.1.6 showed that every positive linear map ϕ form M 2 (C) to M m (C) is decomposable if and only if m ⩽ 3. In [7], [8] and [9] Theorem 1, Størmer gives conditions for decomposability of positive maps; For A be a C * -algebra and linear map ϕ is decomposable if and only if for all n ∈ N whenever (x ij ) and (x ji ) belong to M n (A) + . Choi [4] gave the first example of indecomposable map, for a 3-dimension case.…”