Witnessing macroscopic entanglement in a staggered magnetic field by Hide, J, Son, W, Lawrie, I, Vedral, V

“…Using single-site entropy and by constructing an entanglement witness, we search for the existence of entanglement when the system is at absolute zero, as well as in thermal equilibrium. Although the role of the alternating magnetic field b is, in general, to suppress entanglement as do B and T, we find that when T=0, introducing b allows the existence of entanglement even when the uniform magnetic field B is arbitrarily large. …”

Heat capacity as an indicator of entanglement by Wiesniak, M, Vedral, V, Brukner, C

“…The idea is that if the system was in a separable state, then for certain Hamiltonians heat capacity would not tend asymptotically to zero as the temperature approaches absolute zero. Since this would contradict the third law of thermodynamics, one concludes that the system must contain entanglement. …”