Comment on "Two Fundamental Experimental Tests of Nonclassicality with Qutrits"

TL;DR

This paper defends a previous qutrit experiment as a valid test of noncontextuality inequalities, clarifying measurement contexts and countering claims that it tested a different inequality.

Contribution

The authors clarify their experimental methodology, demonstrating it properly tests Klyachko et al.'s noncontextuality inequality and addresses prior criticisms.

Findings

Confirmed the experiment tests Klyachko et al.'s inequality

Clarified measurement context handling

Reinforced validity of the noncontextuality test

Abstract

In a recent paper [arXiv:1301.2887] Ahrens et al. claim that our "(...) experiment on qutrits does not test Klyachko et al.'s inequality, but an inequality with extra correlations" and that the "(...) experiment cannot be considered a proper test of a noncontextuality inequality, since the same observable is measured with different setups in different contexts". We disagree with these claims. In this note we briefly re-state how our test of the non-contextuality inequality was constructed. We explain how we keep the context of measurements when switching between different terms of the tested inequality, and we argue that we did in fact test the Klyachko, Can, Binicioglu and Shumovsky inequality. In doing so, we also clarify why our experiment is indeed a proper test of noncontextual realism.