Atom interferometry and the Einstein equivalence principle

TL;DR

This paper reviews how atom interferometers can test the weak equivalence principle by comparing atomic and classical free-fall accelerations, highlighting their insensitivity to gravitational redshift effects.

Contribution

It demonstrates that symmetric atom interferometers can test the weak equivalence principle through phase shift analysis, emphasizing their limitations regarding gravitational redshift.

Findings

Atom interferometers can test the weak equivalence principle.

Phase shift difference is zero for quadratic Lagrangians.

Insensitive to gravitational redshift effects.

Abstract

The computation of the phase shift in a symmetric atom interferometer in the presence of a gravitational field is reviewed. The difference of action-phase integrals between the two paths of the interferometer is zero for any Lagrangian which is at most quadratic in position and velocity. We emphasize that in a large class of theories of gravity the atom interferometer permits a test of the weak version of the equivalence principle (or universality of free fall) by comparing the acceleration of atoms with that of ordinary bodies, but is insensitive to that aspect of the equivalence principle known as the gravitational redshift or universality of clock rates.