Martynas Skrabulis, Martin Colombano Sosa, Nicola Carlon Zambon, Andrei Militaru, Massimiliano Rossi, Martin Frimmer, Lukas Novotny
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 an impulsive-force resolution as small as 6.9 keV/c, a value 0.6 dB below the sensor's zero-point value.