Wavefront Mapping for Absolute Atom Interferometry

TL;DR

This paper presents a method to measure and correct wavefront distortions in atom interferometers, significantly reducing systematic errors in gravitational acceleration measurements.

Contribution

The authors introduce an in situ spatially resolved phase measurement technique to characterize and correct wavefront bias in atom interferometry.

Findings

Wavefront bias can be measured with 1 mrad uncertainty.

Controllable curvature of Raman light helps identify wavefront distortions.

Finite-size effects influence phase curvature measurements.

Abstract

Wavefront distortions are a leading source of systematic uncertainty in light-pulse atom interferometry, limiting absolute measurements of gravitational acceleration at the 30 nm/s$^2$ level. Here, we demonstrate in situ spatially resolved measurement of the interferometer phase in a Mach-Zehnder atom interferometer as a tool to characterize and correct wavefront bias. By introducing controllable curvature of the Raman light using an adjustable collimation retro-reflector, we show that the bias due to parabolic wavefront curvature can be measured with 1 mrad uncertainty and that finite-size corrections impact the measured phase curvature. This measurement process could be adopted in optimized atom interferometer gravimeters to reduce wavefront bias uncertainty below the nm/s$^2$ level.