Signatures of linearized gravity in atom interferometers: A simplified computational framework

TL;DR

This paper presents a simplified computational framework for calculating relativistic gravitational phase shifts in atom interferometers, analyzing their response to gravitational waves and Newtonian noise, with implications for future experiments.

Contribution

It introduces a general, simplified method to compute relativistic effects in atom interferometers and applies it to realistic noise sources and gravitational signals.

Findings

Doppler phase shift can be significant due to Newtonian noise.

Atom interferometers can detect gravitational waves in specific configurations.

Newtonian noise may exceed shot noise, affecting experimental sensitivity.

Abstract

We develop a general framework for calculating the leading-order, general relativistic contributions to the gravitational phase shift in single-photon atom interferometers within the context of linearized gravity. We show that the atom gradiometer observable, which only depends on the atom interferometer propagation phase, can be written in terms of three distinct contributions: the Doppler phase shift, which accounts for the tidal displacement of atoms along the baseline, the Shapiro phase shift, which accounts for the delay in the arrival time of photons at atom-light interaction points, and the Einstein phase shift, which accounts for the gravitational redshift measured by the atoms. For specific atom gradiometer configurations, we derive the signal and response functions for two physically motivated scenarios: (i) transient gravitational waves in the transverse-traceless gauge and, for the first time, in the proper detector frame, and (ii) transient massive objects sourcing weak and slow-varying Newtonian potentials. We find that the Doppler contribution of realistic Newtonian noise sources (e.g., a freight truck or a piece of space debris) at proposed atom gradiometer experiments, such as AION, MAGIS and AEDGE, can exceed the shot noise level and thus affect physics searches if not properly subtracted.