Demonstration of an ultrahigh-sensitivity atom-interferometry absolute gravimeter

TLDR

The authors present an ultrahigh‑sensitivity 87Rb atom‑interferometer gravimeter and demonstrate a calibration experiment to directly evaluate its sub‑μGal resolution. The gravimeter uses a 87Rb atom interferometer with stimulated Raman transitions, a 2D magneto‑optical trap to increase atom number, and an improved optical phase‑locked loop to reduce Raman beam phase noise. The device achieves a short‑term sensitivity of 4.2 μGal/√Hz, twice the previous best, and residual vibration noise of 1.2 μGal/√Hz suggests a potential one‑order‑of‑magnitude improvement in absolute gravity measurement.

Abstract

We present an ultrahigh-sensitivity gravimeter based on an ${}^{87}$Rb atom interferometer using stimulated Raman transitions. Compared with our previous work, a two-dimensional magneto-optical trap is added in the new gravimeter to increase the atom number and improve the detection signal-to-noise ratio, and a better optical phase-locked loop system is used to reduce the phase noise of Raman beams. Benefiting from these efforts and the excellent performance of the active vibration isolator, a short-term sensitivity of about 4.2 $\ensuremath{\mu}\text{Gal}/\sqrt{\text{Hz}}$ ($1\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{Gal}=1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ $\text{m}/{\text{s}}^{2}$) is reached, which improves the sensitivity by a factor of 2 compared with the former best reported value. By a modulation experiment, we further indicate that the residual vibration noise contribution is about 1.2 $\ensuremath{\mu}\text{Gal}/\sqrt{\text{Hz}}$, which implies a possible improvement over the present absolute gravity measurement level by about one order of magnitude. Moreover, we demonstrate a calibration experiment to directly evaluate the sub-$\ensuremath{\mu}$Gal resolution of our gravimeter.