About possible extensions of quantum theory

TL;DR

The paper challenges recent claims that quantum theory cannot be extended to improve predictive power, arguing that such claims rely on flawed assumptions about free will and no-signaling constraints.

Contribution

It demonstrates that the argument against extensions of quantum theory is based on an improper use of free will assumptions, clarifying the relationship between free will and no-signaling.

Findings

The claim that quantum theory cannot be extended is flawed.

Free will should not be equated with no-signaling constraints.

Bohmian Mechanics remains compatible with free will.

Abstract

Recently it has been claimed that no extension of quantum theory can have improved predictive power, the statement following, according to the authors, from the assumptions of free will and of the correctness of quantum predictions concerning the correlations of measurement outcomes. Here we prove that the argument is basically awed by an inappropriate use of the assumption of free will. In particular, among other implications, the claim, if correct, would imply that Bohmian Mechanics is incompatible with free will. This statement, appearing in the paper, derives from the unjustified identification of free will with the no-signaling constraint and of a purely formal and not physical use of such a constraint.