Levitated optomechanics at the photon recoil limit

Abstract

Optomechanics explores the coupling between light and the mechanical motion of nanoscopic matter. Optical levitation offers a promising avenue in the investigation of macroscopic quantum behavior by using glass nanoparticles that are physically detached from the environment. Our goal in this thesis is to bring a levitated nanoparticle to the quantum ground state of its center-of-mass motion using phase-sensitive feedback that is conditioned on high precision interferometric measurements of the particle's position. We cool the harmonic motion of the nanoparticle from ambient to microkelvin temperatures and measure its reheating rate under the influence of the radiation field. The limit reached corresponds to that of photon recoil heating, which will set bounds to the coherence times of future quantum states and protocols in our system. We quantitatively characterize the role of laser intensity noise for demanding applications in ultrasensitive force detection and find that the system is in the regime of strong measurement backaction. Finally, protocols to interrogate the classical to quantum transition are proposed.