Two Fundamental Experimental Tests of Nonclassicality with Qutrits

TL;DR

This paper reports two key experiments demonstrating quantum advantages with qutrits by violating classical inequalities, confirming nonclassicality and contextuality in three-level quantum systems.

Contribution

It presents the first experimental violation of Wright's inequality and Klyachko et al.'s noncontextuality inequality using qutrits with consistent measurement procedures.

Findings

Violation of Wright's inequality confirms quantum advantage.

Violation of Klyachko et al.'s inequality demonstrates contextuality.

Measurement order does not affect the inequality violations.

Abstract

We report two fundamental experiments on three-level quantum systems (qutrits). The first one tests the simplest task for which quantum mechanics provides an advantage with respect to classical physics. The quantum advantage is certified by the violation of Wright's inequality, the simplest classical inequality violated by quantum mechanics. In the second experiment, we obtain contextual correlations by sequentially measuring pairs of compatible observables on a qutrit, and show the violation of Klyachko et al.'s inequality, the most fundamental noncontextuality inequality violated by qutrits. Our experiment tests exactly Klyachko et al.'s inequality, uses the same measurement procedure for each observable in every context, and shows that the violation does not depend on the order of the measurements.