Proposal for testing Einstein's moon using three-time correlations

TL;DR

This paper proposes a novel experimental scheme using three-time correlations to test Einstein's question about the moon's existence in superposition, aiming to challenge macroscopic realism without relying on statistical analysis.

Contribution

It introduces a new temporal GHZ-based method for testing macroscopic realism directly through three-time correlations, avoiding statistical complexities.

Findings

Proposes a three-time correlation test for macroscopic realism.

Avoids statistical analysis in testing quantum superposition.

Provides a clearer way to challenge classical notions of macroscopic objects.

Abstract

Quantum mechanics has predicted many counterintuitive phenomena in daily life, and has changed our view of the world. Among such predictions, the existence of a macroscopic object in superposition is especially unbelievable. As Einstein asked, "Do you really believe that the moon exists only when you look at it?". However, recent experimental results on a mesoscopic scale will ultimately require us to dismiss commonsense so-called macroscopic reality. Leggett and Garg applied the Bell scheme for testing local realism to the time evolution of a macroscopic two-state system, and proposed a temporal version of the Bell inequality (the Leggett-Garg (LG) inequality) for testing macroscopic realism. However, as with the Bell inequality, the statistical approach behind this scheme may be less effective in showing clear incompatibility. Here we propose a temporal version of the Greenberger-Horne-Zeilinger (GHZ) scheme without statistical treatment for testing Einstein's moon using three-time correlations.