Free-fall non-universality in quantum theory

TL;DR

This paper demonstrates that quantum wave-function spreading causes deviations from universal free fall, suggesting that quantum particles' trajectories depend on their internal properties, which can be measured with atom interferometry.

Contribution

It introduces a quantum-theoretic framework incorporating Einstein equivalence and covariance, revealing non-universality of free fall in quantum particles.

Findings

Free-fall trajectories depend on internal properties of quantum particles.

Quantitative estimates of non-universality are within measurable range.

Atom interferometry can detect deviations from classical free-fall universality.

Abstract

We show by embodying the Einstein equivalence principle - local Poincar\'{e} invariance - and general covariance in quantum theory that wave-function spreading rules out the universality of free fall, i.e. the free-fall trajectory of a quantum (test) particle depends on its internal properties. We provide a quantitative estimate of the free-fall non-universality in terms of the E\"{o}tv\"{o}s parameter, which turns out to be measurable in atom interferometry.