Comment on Consequences of the single-pair measurement of the Bell parameter

TL;DR

This paper clarifies that a recent experiment claiming to measure the Bell parameter on a single photon pair does not actually measure the Bell parameter S, thus not challenging established quantum mechanics principles.

Contribution

It explains that the measured quantity in the experiment differs from the Bell parameter S, reaffirming the validity of existing Bell test conclusions.

Findings

The experiment does not measure the Bell parameter S.

The claimed challenge to Bell inequalities is unfounded.

The experiment does not undermine quantum mechanics interpretations.

Abstract

Genovese and Piacentini [Phys.Rev.A 111, 022204 (2025)] claim that in a recent experiment[S.Virz\`i et al., Quantum Sci. Technol. 9, 045027 (2024)] the Bell parameter was measured on a single pair of photons thus it challenges several conclusions and discussions on the meaning of Bell inequalities as well as certain QM interpretations. We explain that the parameter measured in Virzi et al. experiment it is not the Bell parameter S which was discussed and estimated in many loophole free tests. Therefore, this experiment neither challenges our understanding of Bell Tests nor allows having doubts about Bohr complementarity and contextuality.