The quantum entanglement contained in density matrices

Abstract

We point out that density matrices can only be used to describe quantum states, so the entanglement contained in a density matrix is just quantum entanglement. This means a bipartite state described by a density matrix contains quantum entanglement, unless the density matrix has the form ${\rho }_{AB}={\rho }_A\otimes {\rho }_B$.

5 pages