The sensitivity of a mechanical transducer is ultimately limited by its inherent quantum fluctuations. Here, we use an optically levitated nanoparticle to measure impulsive forces smaller than the particle's zero-point momentum uncertainty. Our approach relies on reversibly squeezing the levitated particle's center-of-mass motion to coherently amplify the perturbation. We demonstrate resolving single impulsive-force kicks as small as 6.9 keV/c, a value 0.6 dB below the sensor's zero-point value.
@article{arxiv.2601.19392,
title = {Nanomechanical sensor resolving impulsive forces below its zero-point fluctuations},
author = {Martynas Skrabulis and Martin Colombano Sosa and Nicola Carlon Zambon and Andrei Militaru and Massimiliano Rossi and Martin Frimmer and Lukas Novotny},
journal= {arXiv preprint arXiv:2601.19392},
year = {2026}
}