Atom gravimeters and gravitational redshift

TL;DR

This paper critiques a recent claim that atom interferometry experiments measured gravitational redshift at the quantum level, clarifying that the interpretation of those experiments was incorrect.

Contribution

It provides a critical analysis refuting the claim that atom interferometry experiments measured gravitational redshift at the Compton frequency.

Findings

The interpretation of previous experiments as measuring gravitational redshift is incorrect.

Clarification of the distinction between quantum clock effects and atom interferometry results.

Reinforcement of the correct understanding of what atom interferometry experiments measure.

Abstract

In a recent paper, H. Mueller, A. Peters and S. Chu [A precision measurement of the gravitational redshift by the interference of matter waves, Nature 463, 926-929 (2010)] argued that atom interferometry experiments published a decade ago did in fact measure the gravitational redshift on the quantum clock operating at the very high Compton frequency associated with the rest mass of the Caesium atom. In the present Communication we show that this interpretation is incorrect.