Comment on "Significant-Loophole-Free Test of Bell's Theorem with Entangled Photons"

TL;DR

This paper critiques a recent Bell test experiment, arguing that a broad class of local hidden-variable theories, especially those involving background fields, remain viable due to the freedom-of-choice loophole.

Contribution

It highlights that background-based local hidden-variable theories can evade the conclusions of recent loophole-free Bell tests.

Findings

Background-based theories exploit the freedom-of-choice loophole

Such theories can be modeled with fluid mechanics systems

They challenge the universality of Bell test conclusions

Abstract

In a recent article Giustina et al. [Phys. Rev. Lett. 115, 250401 (2015)] report on an advanced Bell experiment, simultaneously closing loopholes for local hidden-variable theories. The authors claim that 'local realism' has been refuted, unless 'truly exotic hypotheses' are made. Here I argue that a particularly wide and natural class of local hidden-variable theories survives, for instance when the hidden variables describe a background field. Such background-based theories exploit the freedom-of-choice loophole, which cannot be closed for this type of hidden variables. The dynamics of such models can be illustrated by existing systems, e.g. from fluid mechanics.