Entanglement observables and witnesses for interacting quantum spin systems
Lian-Ao Wu, Somshubhro Bandyopadhyay, M. S. Sarandy, Daniel A. Lidar · Physical Review A · 2005
We discuss the detection of entanglement in interacting quantum spin systems. First, thermodynamic Hamiltonian-based witnesses are computed for a general class of one-dimensional spin-$1∕2$ models. Second, we introduce optimal bipartite entanglement observables. We show that a bipartite entanglement measure can generally be associated with a set of independent two-body spin observables whose expectation values can be used to witness entanglement. The number of necessary observables is ruled by the symmetries of the model. Illustrative examples are presented.