On universal decoherence under gravity: a perspective through the Equivalence Principle

TL;DR

This paper reexamines gravitationally induced decoherence, suggesting it arises from mass-dependent de Broglie wave dispersion rather than gravity itself, and explores the role of the Equivalence Principle in this context.

Contribution

It offers an alternative perspective on gravity-induced decoherence, emphasizing the kinematic effects of gravity and the potential violation of the Equivalence Principle.

Findings

Decoherence arises from mass differences, not gravity directly.

Visibility can be restored by adjusting detector velocity.

Dephasing may occur if the Equivalence Principle is violated.

Abstract

In Nature Phys. 11, 668 (2015) (Ref. [1]), a composite particle prepared in a pure initial quantum state and propagated in a uniform gravitational field is shown to undergo a decoherence process at a rate determined by the gravitational acceleration. By assuming Einstein's Equivalence Principle to be valid, we demonstrate, first in a Lorentz frame with accelerating detectors, and then directly in the Lab frame with uniform gravity, that the dephasing between the different internal states arise not from gravity but rather from differences in their rest mass, and the mass dependence of the de Broglie wave's dispersion relation. We provide an alternative view to the situation considered by Ref. [1], where we propose that gravity plays a kinematic role in the loss of fringe visibility by giving the detector a transverse velocity relative to the particle beam; visibility can be easily recovered by giving the screen an appropriate uniform velocity. We finally propose that dephasing due to gravity may in fact take place for certain modifications to the gravitational potential where the Equivalence Principle is violated.