Class of positive partial transposition states
Dariusz Chruściński, Andrzej Kossakowski · Physical Review A · 2006
We construct a class of quantum bipartite $d\ensuremath{\bigotimes}d$ states which are positive under partial transposition (PPT states). This class is invariant under the maximal commutative subgroup of $\mathrm{U}(d)$ and contains as special cases many well-known examples of PPT states. States from our class provide criteria for testing the indecomposability of positive maps. Such maps are crucial for constructing entanglement witnesses.