Development of Control System and RF Synthesis Chain for Absolute Quantum Gravimeter at TCG-CREST

Accurate and stable acceleration due to gravity measurements are critical for mapping spatial and temporal density variation of Earth’s subsurface, precision inertial navigation, advanced metrology, detecting underground structures, and many other applications. For precise measurement of gravity, absolute quantum gravimeter (AQG) exploits atomic matter wave interference to achieve exceptional sensitivity (≤ 1 μGal) as well as offering long-term stability and mitigates of mechanical drifts. Gravity measurement with an AQG involves several processes such as cooling and trapping Rubidium-87 (⁸⁷Rb) atoms in a magneto-optical trap (MOT), followed by optical molasses and polarization gradient cooling (PGC), state preparation, atom-interferometry, and population detection. The operational sequences in these processes demand extremely precise event triggering and synchronized instrument operation with sub-microsecond accuracy. Since the sensitivity and accuracy of gravity measurements with an AQG are highly dependent on timing precision, any deviation in the sequence can introduce phase noise and systematic errors, ultimately affecting measurement fidelity. In this article, we describe a control architecture of an absolute cold atom gravimeter and the implementation of timing sequences. The design of a radiofrequency synthesizer is also described, crucial for ultra-fast switching and frequency/power control of laser beams in an AQG.