Optimality of entanglement witnesses constructed from arbitrary permutations.

The optimality of a class of entanglement witnesses constructed from any permutation $$\pi $$ for any $$n\otimes n$$ bipartite systems is investigated. A necessary and sufficient condition is presented for such entanglement witnesses to be optimal, and thus, a class of optimal entanglement witnesses constructed by permutations is obtained. [ABSTRACT FROM AUTHOR]