Entanglement detection via quantum Fisher information in an XY dimer

Abstract

We use an entanglement criterion that is based on the quantum Fisher information to detect entanglement in thermal mixed states of an XY dimer. In the absence of an external magnetic field we find that it detects entanglement only in the anisotropic regions beyond the Ising line. Entanglement is destroyed at high temperatures, and this criterion is only able to detect entanglement at a lower threshold temperature than concurrence.