Controlling the Multiport Nature of Bragg Diffraction in Atom Interferometry

TL;DR

This paper investigates and mitigates the multi-port effects of Bragg diffraction in atom interferometers, enhancing measurement precision and enabling higher momentum transfer through optimized pulse shaping and systematic control techniques.

Contribution

It introduces methods to suppress parasitic interferometers and phase shifts, and demonstrates improved sensitivity and higher momentum transfer in atom interferometry.

Findings

Gaussian Bragg pulses minimize systematic shifts

Parasitic interferometers are suppressed by a 'magic' pulse duration

Achieved 6.6 Mrad phase measurement with 310 ħk momentum transfer

Abstract

Bragg diffraction has been used in atom interferometers because it allows signal enhancement through multiphoton momentum transfer and suppression of systematics by not changing the internal state of atoms. Its multi-port nature, however, can lead to parasitic interferometers, allows for intensity-dependent phase shifts in the primary interferometers, and distorts the ellipses used for phase extraction. We study and suppress these unwanted effects. Specifically, phase extraction by ellipse fitting and the resulting systematic phase shifts are calculated by Monte Carlo simulations. Phase shifts arising from the thermal motion of the atoms are controlled by spatial selection of atoms and an appropriate choice of Bragg intensity. In these simulations, we found that Gaussian Bragg pulse shapes yield the smallest systematic shifts. Parasitic interferometers are suppressed by a "magic" Bragg pulse duration. The sensitivity of the apparatus was improved by the addition of AC Stark shift compensation, which permits direct experimental study of sub-part-per-billion (ppb) systematics. This upgrade allows for a 310\,$\hbar k$ momentum transfer, giving an unprecedented 6.6\,Mrad measured in a Ramsey-Bord\'e interferometer.