Scaling of macroscopic superpositions close to a quantum phase transition

摘要

It is well known that in a quantum phase transition (QPT), entanglementremains short ranged [Osterloh et al., Nature 416 608-610 (2005)]. We ask ifthere is a quantum property entailing the whole system which diverges near thispoint. Using the recently proposed measures of quantum macroscopisity, we showthat near a quantum critical point, it is the effective size of macroscopicsuperposition between the two symmetry breaking states which grows to the scaleof system size and its derivative with respect to the coupling shows bothsingular behavior and scaling properties.