Optomechanical inertial reference for atom interferometry

Abstract: Atom interferometers are among the most sensitive inertial sensors, yet deployment outside the laboratory is limited by vibration noise, conventionally mitigated by external sensors or bulky isolation. Here we demonstrate a hybrid inertial sensor which fuses an optomechanical resonator and an atom interferometer by exploiting the resonator's test mass as the interferometer's reference mirror. This allows for better correlation than with two separate sensors, whose unknown transfer function is replaced by the static response of one mechanical element. The resonator achieves a displacement sensitivity of $8.6\cdot 10<sup>{-15}$ m/$\sqrt{\mathrm{Hz}}$ with suppressed 1/f noise and yields a minimum acceleration sensitivity of $1.1\cdot10<sup>{-6}$ m/s$<sup>2$/$\sqrt{\mathrm{Hz}}$ over a bandwidth extending from sub-Hertz to 2.5 kHz. Under ambient laboratory conditions the integrated system removes vibration-induced phase ambiguity for accelerations up to $50\cdot 10<sup>{-3}$ m/s$<sup>2$ and reaches the interferometer's technical noise limit, which a commercial force-balance accelerometer does not. Because the resonance-tracking readout is largely independent of the mechanical design, the architecture transfers directly to other precision sensing platforms.