Quantum squeezing of a levitated nanomechanical oscillator

Abstract: Manipulating the motions of macroscopic objects near their quantum mechanical uncertainties has been desired in diverse fields, including fundamental physics, sensing, and transducers. Despite significant progresses in ground-state cooling of a levitated solid particle, realizing non-classical states of its motion has been elusive. Here, we demonstrate quantum squeezing of the motion of a single nanoparticle by rapidly varying its oscillation frequency. We reveal significant narrowing of the velocity variance to $-4.9(1)$~dB of that of the ground state via free-expansion measurements. To quantitatively confirm our finding, we develop a method to accurately measure the displacement of the nanoparticle by referencing an optical standing wave. Our work shows that a levitated nanoparticle offers an ideal platform for studying non-classical states of its motion and paves the way for its applications in quantum sensing, as well as for exploring quantum mechanics at a macroscopic scale.