On decomposability of positive maps between M 2 and M n
Abstract
A map $\phi:M_m(\bC)\to M_n(\bC)$ 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 $\phi: M_2(\bC) \to M_3(\bC)$ is given.