Coherence, asymmetry, and quantum macroscopicity
Hyukjoon Kwon, Chae-Yeun Park, Kok Chuan Tan, Daekun Ahn, Hyunseok Jeong · Physical Review A · 2018
We investigate a measure of quantum coherence and its extension to quantify quantum macroscopicity. The coherence measure can also quantify the asymmetry of a quantum state with respect to a given group transformation. We then show that a weighted sum of asymmetry in each mode can be applied as a measure of macroscopic coherence. To exclude the effects of microscopic superpositions, we suggest a method to introduce a cutoff to the weighted sum that will specify the macroscopic portion of the coherence. This cutoff may be interpreted as the fuzziness for a given measurement outcome. Based on the suggested measures, we investigate the quantum macroscopicity for particular concrete examples in $N$-partite spin systems.