Test of macroscopic realism with coherent light

TL;DR

This paper demonstrates a violation of macro-realism using coherent light and Leggett-Garg inequality tests, showing that quantum effects can be observed at a macroscopic scale through interference and weak measurements.

Contribution

It presents the first violation of macro-realism with coherent light using an exact weak measurement model, enabling direct and non-invasive verification.

Findings

Confirmed Leggett-Garg inequality violation with coherent light

Demonstrated destructive interference as evidence of macro-realism violation

Showed violation is independent of measurement invasiveness

Abstract

Macro-realism is a fundamental feature of classical world that contradicts with the quantum theory. An elegant method of testing macrorealism is to apply the Leggett-Garg inequality (LGI), but the non-invasivity of measurement is challenging in practice. In this work, we report the LGI violation of path observable in a composite interference experiment with coherent light. Experiment results confirm the occurrence of destructive interference providing per se as evidence of macro-realism violation. And by using an exact weak measurement model in the present experiment, the advantage that the violation of realism is independent of the invasive strength allows the realization of direct measurement and strengthens the persuasion of verification at the macroscopic scale.