Let S ( H A ⊗ ⊗ H B ) be the space of all states, i.e., Hermitian positive semi-definite operators with trace one, over the bipartite Hilbert space H A ⊗ ⊗ H B . An entanglement measure is a function μ μ : S ( H A ⊗ ⊗ H B ) → → R ≥ ≥ 0 such that: