Tracking the Vector Acceleration with a Hybrid Quantum Accelerometer Triad

Robust and accurate acceleration tracking remains a challenge in many fields. For geophysics and economic geology, precise gravity mapping requires onboard sensors combined with accurate positioning and navigation systems. Cold-atom-based quantum inertial sensors can potentially provide such high-precision instruments. However, current scalar instruments require precise alignment with vector quantities. Here, we present the first hybrid three-axis accelerometer exploiting the quantum advantage to measure the full acceleration vector by combining three orthogonal atom interferometer measurements with a classical navigation-grade accelerometer triad. Its ultra-low bias permits tracking the acceleration vector over long timescales -- yielding a 50-fold improvement in stability ($6 \times 10^{-8}~g$) over our classical accelerometers. We record the acceleration vector at a high data rate (1 kHz), with absolute magnitude accuracy below 10 $\mu g$, and pointing accuracy of 4 $\mu$rad. This paves the way toward future strapdown applications with quantum sensors and highlights their potential as future inertial navigation units.