Measuring High-Order Spatial Derivatives of the Vertical Gravity Field by Stacking Atom Interferometers

Light-pulse atom interferometry has been widely used to measure fundamental physics constants and test the laws of physics. Nowadays, compact atom interferometers have been developed to measure local gravity and the gravity gradient with high sensitivity and accuracy. Beyond the gravity gradient, the third-order derivative of the gravity field, the so-called gravity curvature, is sensitive to the changes in density. If made transportable, such measurements will open the door for providing horizontal resolutions in mining exploration and detecting near-surface or shallow density structures. We aim to develop a compact atomic gravimeter and implement atom interferometers at three vertically separated heights, obtaining gravity, gradient, and gravity curvature measurements simultaneously. These measurements are currently limited to being laboratory-based due to the complexity of the setup. We demonstrated a magneto-optical trap inside a back-to-back conical mirror for ⁸⁷Rb atoms and implemented a vertical atom interferometer, with the capability to scale it into three atom interferometers using a single laser beam. We developed a compact and versatile laser system, compatible with 780-nm diode and 1560-nm fiber lasers to produce all the frequencies for laser cooling, driving Raman transition, and detecting atoms. We are assembling a 1-meter-long vacuum chamber to demonstrate three simultaneous atom interferometers using a single laser beam and constructing a transportable platform for gravity surveys.