Negativity as a distance from a separable state
Michael Khasin, Ronnie Kosloff, D. Steinitz · Physical Review A · 2007
The computable measure of the mixed-state entanglement, the negativity, is shown to admit a clear geometrical interpretation, when applied to Schmidt-correlated (SC) states: the negativity of a SC state equals a distance of the state from a pertinent separable state. As a consequence, the Peres-Horodecki criterion of separability is both necessary and sufficient for SC states. Another remarkable consequence is that the negativity of a SC can be estimated ``at a glance'' on the density matrix. These results are generalized to mixtures of SC states, which emerge in bipartite evolutions with additive integrals of motion.