Lower bounds on the size of general Schr\"odinger-cat states from experimental data

TL;DR

This paper develops a method to quantify the quantum coherence of macroscopic Schrödinger-cat states using experimental data, providing lower bounds on their effective size with results up to 70.

Contribution

It introduces a way to analyze actual experimental data to determine the quantum coherence extent of macroscopic states using quantum Fisher information.

Findings

Lower bounds on quantum coherence size up to 70.

Application to photonic and atomic systems.

Bridging theory and experiment in macroscopic quantum states.

Abstract

Experimental progress with meso- and macroscopic quantum states (i.e., general Schrodinger-cat states) was recently accompanied by theoretical proposals on how to measure the merit of these efforts. So far, experiment and theory were disconnected as theoretical analysis of actual experimental data was missing. Here, we consider a proposal for macroscopic quantum states that measures the extend of quantum coherence present in the system. For this, the quantum Fisher information is used. We calculate lower bounds from real experimental data. The results are expressed as an "effective size", that is, relative to "classical" reference states. We find remarkable numbers of up to 70 in photonic and atomic systems.