Quantum Field-Theoretic Predictions of {\Psi}-Epistemic Models of Quantum Mechanics

TL;DR

This paper demonstrates that under Lorentz symmetry, $ ext{ extPsi}$-epistemic models can produce measurable deviations from standard quantum field theory predictions, opening new avenues for experimental tests of quantum foundations.

Contribution

It shows that $ ext{ extPsi}$-epistemic models respecting Lorentz symmetry can lead to observable differences in particle physics experiments, without needing a relativistic ontological framework.

Findings

Deviations in polarized scattering cross sections from quantum field theory predictions.

Modifications of decay widths due to $ ext{ extPsi}$-epistemic models.

Lorentz symmetry alone suffices to produce these deviations.

Abstract

$\Psi$-epistemic models of quantum mechanics imply that the quantum state does not correspond to physical reality, but instead reflects the observer's knowledge of the underlying quantum system. The epistemic view of the quantum state has the potential to shed light on several foundational problems of quantum theory and has attracted considerable attention in the literature. On the other hand, the Pusey-Barrett-Rudolph theorem demonstrated that broad classes of $\psi$-epistemic models must lead to predictions that deviate from those of quantum mechanics. Although the original theorem involved entangled joint measurements on composite systems, alternative no-go theorems involving measurements on single quantum systems were developed shortly thereafter. Experimental investigations of the deviations predicted by $\psi$-epistemic models from quantum mechanics are still ongoing. So far, such tests have been performed within the framework of non-relativistic quantum mechanics and predominantly rely on quantum information based measurement procedures. In this work, assuming that $\psi$-epistemic models respect Lorentz symmetry, we show that they can give rise to deviations from standard quantum field-theoretic predictions through modifications of polarized scattering cross sections and decay widths. Our results do not require a relativistic formulation of ontological models or of the Harrigan-Spekkens criterion; Lorentz symmetry alone is sufficient. The present work constitutes a proof-of-principle study demonstrating that particle physics tests of the ontological status of the quantum state are possible and that $\psi$-epistemic models may exhibit experimentally distinguishable signatures in particle phenomenology.