Exposed positive maps in matrix algebras define a dense subset of extremalView original: http://arxiv.org/abs/1201.5995
maps. We provide a class of indecomposable positive maps in the algebra of 2n x
2n complex matrices with n > 1. It is shown that for n \leq 6 these maps are
exposed and it is conjectured that this property holds for all n > 1. Such maps
define the strongest tool in entanglement theory to discriminate between
separable and entangled states.