A Simple Test of the Equivalence Principle(s) for Quantum Superpositions

TL;DR

This paper proposes a straightforward experimental test for the quantum equivalence principle using a trapped atom, aiming to detect violations through forbidden transitions when external conditions are altered.

Contribution

It introduces a simple experimental setup to test the quantum equivalence principle with superpositions of internal energy states, extending previous theoretical work.

Findings

Violations manifest as forbidden transitions when magnetic fields are switched off.

The experiment can set bounds on phenomenological violation parameters.

Classical weak equivalence principle tested via free fall of the apparatus.

Abstract

We propose a simple experimental test of the quantum equivalence principle introduced by Zych and Brukner [arXiv:1502.00971], which generalises the Einstein equivalence principle to superpositions of internal energy states. We consider a harmonically-trapped spin-$\frac12$ atom in the presence of both gravity and an external magnetic field and show that when the external magnetic field is suddenly switched off, various violations of the equivalence principle would manifest as otherwise forbidden transitions. Performing such an experiment would put bounds on the various phenomenological violating parameters. We further demonstrate that the classical weak equivalence principle can be tested by suddenly putting the apparatus into free fall, effectively 'switching off' gravity.