Parametric Feedback Cooling of Levitated Optomechanics in a Parabolic   Mirror Trap
  We demonstrate a simple and robust geometry for optical trapping in vacuum of a single nanoparticle based on a parabolic mirror and the optical gradient force, and we demonstrate rapid parametric feedback cooling of all three motional degrees of freedom from room temperature to a few mK. A single laser at 1550nm, and a single photodiode, are used for trapping, position detection, and cooling for all three dimensions. Particles with diameters from 26nm to 160nm are trapped without feedback to 10$^{-5}$mbar and with feedback engaged the pressure is reduced to 10$^{-6}$mbar. Modifications to the harmonic motion in the presence of noise and feedback are studied, and an experimental mechanical quality factor $>4\times 10^7$ is estimated. 
Jamie Vovrosh, Muddassar Rashid, David Hempston, James Bateman, Mauro   Paternostro and Hendrik Ulbricht
quant-ph physics.optics