Probing the limits of correlations in an indivisible quantum system

TL;DR

This study uses a trapped ion to test quantum contextuality in a single qutrit with increasing measurement complexity, confirming quantum predictions up to 101 observables despite experimental imperfections.

Contribution

It demonstrates the violation of non-contextuality inequalities in a single quantum system with up to 101 observables, exploring the limits of quantum correlations.

Findings

Violates classical bounds by up to 25 standard deviations

Confirms quantum predictions up to 101 observables

Experimental imperfections obscure correlations beyond 101 observables

Abstract

We employ a trapped ion to study quantum contextual correlations in a single qutrit using the 5-observable KCBS inequality, which is arguably the most fundamental non-contextuality inequality for testing Quantum Mechanics (QM). We quantify the effect of systematics in our experiment by purposely scanning the degree of signaling between measurements, which allows us to place realistic bounds on the non-classicality of the observed correlations. Our results violate the classical bound for this experiment by up to 25 standard deviations, while being in agreement with the QM limit. In order to test the prediction of QM that the contextual fraction increases with the number of observables, we gradually increase the complexity of our measurements from 5 up to 121 observables. We find stronger-than-classical correlations in all prepared scenarios up to 101 observables, beyond which experimental imperfections blur the quantum-classical divide.