# Sr atom interferometry with the optical clock transition as a gravimeter and a gravity gradiometer

## TL;DR

This paper demonstrates a novel atom interferometry gravimeter and gravity gradiometer using strontium atoms' optical clock transition, achieving high sensitivity and longer interrogation times, paving the way for advanced quantum sensors.

## Contribution

First realization of an atomic interferometry gravimeter based on a single-photon clock transition with detailed noise characterization and improved measurement duration.

## Key findings

- Achieved a gravitational acceleration sensitivity of 1.7×10⁻⁵
- Demonstrated a differential phase sensitivity of 1.53 rad/√Hz
- Extended interferometry time to 30 ms, surpassing previous limits

## Abstract

We characterize the performance of a gravimeter and a gravity gradiometer based on the $^{1}$S$_{0}$-$^3$P$_0$ clock transition of strontium atoms. We use this new quantum sensor to measure the gravitational acceleration with a relative sensitivity of $1.7\times10^{-5}$, representing the first realisation of an atomic interferometry gravimeter based on a single-photon transition. Various noise contributions to the gravimeter are measured and characterized, with the current primary limitation to sensitivity seen to be the intrinsic noise of the interferometry laser itself. In a gravity gradiometer configuration, a differential phase sensitivity of 1.53~rad/$\sqrt{Hz}$ was achieved at an artificially introduced differential phase of $\pi/2$~rad. We experimentally investigated the effects of the contrast and visibility based on various parameters and achieve a total interferometry time of 30~ms, which is longer than previously reported for such interferometers. The characterization and determined limitations of the present apparatus employing $^{88}$Sr atoms provides a guidance for the future development of large-scale clock-transition gravimeters and gravity gradiometers with alkali-earth and alkali-earth-like atoms (e.g., $^{87}$Sr, Ca, Yb).