Bragg gravity-gradiometer using the $^1$S$_0$-$^3$P$_1$ intercombination transition of $^{88}$Sr

TL;DR

This paper demonstrates a highly sensitive gravity gradiometer using strontium atoms and Bragg diffraction, achieving low magnetic sensitivity and showcasing potential for precision gravity measurements and fundamental physics tests.

Contribution

It introduces a novel strontium-based matter-wave gradiometer utilizing Bragg diffraction on the $^1$S$_0$-$^3$P$_1$ transition, with enhanced sensitivity and low magnetic interference.

Findings

Sensitivity of 1.5 x 10^{-5} s^{-2} at 20 ms interferometer time

Magnetic field gradient sensitivity reduced by a factor of 10^5

Successful implementation of double-launch technique from a single MOT cloud

Abstract

We present a gradiometer based on matter-wave interference of alkaline-earth-metal atoms, namely $^{88}$Sr. The coherent manipulation of the atomic external degrees of freedom is obtained by large-momentum-transfer Bragg diffraction, driven by laser fields detuned away from the narrow $^1$S$_0$-$^3$P$_1$ intercombination transition. We use a well-controlled artificial gradient, realized by changing the relative frequencies of the Bragg pulses during the interferometer sequence, in order to characterize the sensitivity of the gradiometer. The sensitivity reaches $1.5 \times 10^{-5}$ s$^{-2}$ for an interferometer time of 20 ms, limited only by geometrical constraints. We observed extremely low sensitivity of the gradiometric phase to magnetic field gradients, approaching a value 10$^{5}$ times lower than the sensitivity of alkali-atom based gradiometers. An efficient double-launch technique employing accelerated red vertical lattices from a single magneto-optical trap cloud is also demonstrated. These results highlight strontium as an ideal candidate for precision measurements of gravity gradients, with potential application in future precision tests of fundamental physics.