Experimental test of high-dimensional quantum contextuality based on contextuality concentration

TL;DR

This paper demonstrates experimentally that high-dimensional quantum systems exhibit increased contextuality, which is a key resource for quantum computation, by testing noncontextuality inequalities in a seven-dimensional system.

Contribution

It introduces a family of noncontextuality inequalities where quantum violation grows with system dimension and experimentally verifies this in a seven-dimensional optical system.

Findings

Quantum violation of inequalities reaches 68.7 standard deviations.

Contextuality per dimension increases with system size.

Experimental setup uses all-optical destructive measurements.

Abstract

Contextuality is a distinctive feature of quantum theory and a fundamental resource for quantum computation. However, existing examples of contextuality in high-dimensional systems lack the necessary robustness required in experiments. Here we address this problem by identifying a family of noncontextuality inequalities whose maximum quantum violation grows with the dimension of the system. At first glance, this contextuality is the single-system version of multipartite Bell nonlocality taken to an extreme form. What is interesting is that the single-system version achieves the same degree of contextuality but uses a Hilbert space of lower dimension. That is, contextuality ``concentrates'' as the degree of contextuality per dimension increases. We show the practicality of this result by presenting an experimental test of contextuality in a seven-dimensional system. By simulating sequences of quantum ideal measurements with destructive measurements and repreparation in an all-optical setup, we report a violation of 68.7 standard deviations of the simplest case of the noncontextuality inequalities identified. Our results advance the investigation of high-dimensional contextuality, its connection to the Clifford algebra, and its role in quantum computation.