Quantification of bound entanglement in two-qutrit states

A bipartite system may be in an entangled state albeit its partially transposed density matrix has only nonnegative eigenvalues. Such states are known to be bound-entangled -no singlet entanglement can be distilled from them-, and constitute a subject of continued interest in quantum information. As bound-entangled states in general are highly mixed the exact quantification of their entanglement in terms of established entanglement measures has remained an open question, and only numerical bounds were known. In this work we discuss a family of highly symmetric two-qutrit states which contains regions with bound entanglement. We identify the entanglement properties of the family and quantify exactly its entanglement by using concurrence-based entanglement monotones.