Sensitive quantum tiltmeter with nanoradian resolution

Abstract

Precision tilt measurements are becoming more and more important in fundamental research and crustal deformation observations. A quantum tiltmeter based on atom interferometry could be among the most stable tiltmeters in theory but is currently constrained by the low resolution. Here, we demonstrate an extremely sensitive quantum tiltmeter with the configuration of a Mach-Zehnder-type atom interferometer for precisely measuring the crustal deformation. The scheme of two pairs of Raman beams sharing one retroreflection mirror effectively increases the scale factor, making this quantum tiltmeter achieve a sensitivity of $40\phantom{\rule{0.28em}{0ex}}\mathrm{nrad}/{\mathrm{Hz}}^{1/2}$ and a resolution of 1.8 nrad within an integration time of 640 s for tilt measurements, which represents an improvement on the sensitivity by a factor of 32 comparing to previous work. The Earth tilt tide lasting for 63 h has been observed with high signal-to-noise ratio by our quantum tiltmeter, which paves the way to study the crustal deformation with a quantum sensor.