Bound entanglement

[8] Bipartite bound entangled states with a positive partial transpose are useless for teleportation, as they cannot lead to a larger fidelity than the classical limit.

[10] It has been shown that bipartite bound entangled states with a positive partial transpose exist in symmetric systems.

It has also been shown that in symmetric systems multipartite bound entangled states exists for which all partial transposes are non-negative.

[11][12] Asher Peres conjectured that bipartite bound entangled states with positive partial transpose cannot violate a Bell inequality.

For large dimensions they approach asymptotically the maximal precision achievable by bipartite quantum states.