Energy as an Entanglement Indicator

Abstract

We explore the method of constructing an entanglement witness utilising the Hamiltonian of a physical system in consideration. Already a partial knowledge of the energy spectrum allows one not only to detect entanglement in thermal equilibrium states, but also to discriminate among its various multipartite genres. We propose an efficient approximate algorithm producing a witness capable of detecting genuine n-partite entanglement. As an illustration, the method is applied to an analytically computable example of anisotropic XXZ Heisenberg chain.