Measures of macroscopicity for quantum spin systems

Florian Fröwis, Wolfgang Dür
2012 New Journal of Physics  
We investigate the notion of "macroscopicity" in the case of large quantum spin systems and provide two main results. First, we motivate the Fisher information as a measure for the macroscopicity of quantum states. Second, we compare the existing literature of this topic. We report on a hierarchy among the measures and we conclude that one should carefully distinguish between "macroscopic quantum states" and "macroscopic superpositions", which is a strict subclass of the former.
doi:10.1088/1367-2630/14/9/093039 fatcat:v5iaeq2dhfajbdcoudm5o7qqtm