Simultaneous cavity cooling of all six degrees of freedom of a levitated nanoparticle

Controlling the motional degrees of isolated, single nanoparticles trapped within optical fields in a high vacuum are seen as ideal candidates for exploring the limits of quantum mechanics in a new mass regime. These systems are also massive enough to be considered for future laboratory tests of the quantum nature of gravity. Recently, the translational motion of trapped particles has been cooled to microkelvin temperatures, but controlling all the observable degrees of freedom, including their orientational motion, remains an important goal. Here we report the control and cooling of all the translational and rotational degrees of freedom of a nanoparticle trapped in an optical tweezer, accomplished by cavity cooling via coherent elliptic scattering. We reached temperatures in the range of hundreds of microkelvins for the translational modes and temperatures as low as 5 mK for the librational degrees of freedom. This work brings within reach applications in quantum science and the study of single isolated nanoparticles via imaging and diffractive methods, free of interference from a substrate.