Abstract
Drawing on results of Choi, Størmer and Woronowicz, we
present a nearly complete characterization of certain important
classes of positive maps. In particular, we construct a general
class of positive linear maps acting between two matrix algebras
ℬ(
) and ℬ(
), where and
are finite-dimensional Hilbert spaces. It turns out
that elements of this class are characterized by operators from
the dual cone of the set of all separable states on
ℬ(⊗). Subsequently, the relation
between entanglements and positive maps is described. Finally, a
new characterization of the cone
ℬ()+⊗ℬ()+ is given.