Two-dimensional quantum motion of a levitated nanosphere

We report on the two-dimensional (2D) dynamics of a levitated nanoparticle in an optical cavity. The motion nanosphere is strongly coupled to cavity field by coherent scattering and heavily cooled plane orthogonal tweezer axis. Due characteristics 2D strong optomechanical coupling, motional sideband asymmetry that reveals quantum nature not limited mere scale factors between Stokes anti-Stokes peaks, as customary optomechanics, but assumes peculiar spectral dependence. introduce discuss effective thermal occupancy quantifies how close system minimum uncertainty state allows us consistently characterize particle motion. By rotating polarization angle beam we tune from one-dimensional (1D) cooling regime, where achieve best 0.51 $\pm$ 0.05, regime which fully exhibits non-classical properties. confinement with 3.4 0.4 along warmest direction around unity one. These results represents major improvement respect previous experiments both considering 1D motion, pave way towards preparation tripartite entangled states novel applications directional force displacement sensing.