All-optical intrinsic atomic gradiometer with sub-20 fT/cm/√Hz sensitivity in a 22 µT earth-scale magnetic field
Abigail R. Perry, Michael Bulatowicz, Michael Larsen, Thad Walker, Robert Wyllie
Abstract
In this work we demonstrate a high sensitivity atomic gradiometer capable of operation in earth-field level environments. We apply a light-pulse sequence at four times the Larmor frequency to achieve gradiometer sensitivity <20 fT/cm/ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msqrt> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mtext>H</mml:mtext> </mml:mrow> <mml:mi>z</mml:mi> </mml:msqrt> </mml:math> at the finite field strength of 22 µ T. The experimental timing sequence can be tuned to the field magnitude of interest. Our all-optical scalar gradiometer performs a differential measurement between two regions of a single vapor cell on a 4 cm baseline. Our results pave the way for extensions to operation in higher dimensions, vector sensitivity, and more advanced gradiometers.