Measures of macroscopicity for quantum spin systems

Abstract

We investigate the notion of "macroscopicity" in the case of large quantum\nspin systems and provide two main results. First, we motivate the Fisher\ninformation as a measure for the macroscopicity of quantum states. Second, we\ncompare the existing literature of this topic. We report on a hierarchy among\nthe measures and we conclude that one should carefully distinguish between\n"macroscopic quantum states" and "macroscopic superpositions", which is a\nstrict subclass of the former.\n