Abstract
Methods for controlling the motion of single particles, optically
levitated in vacuum, have developed rapidly in recent years. The
technique of cold damping makes use of
feedback-controlled, electrostatic forces to increase dissipation
without introducing additional thermal fluctuations. This process has
been instrumental in the ground-state cooling of individual
electrically charged nanoparticles. Here we show that the same method
can be applied to a pair of nanoparticles, coupled by optical binding
forces. These optical binding forces are about three orders of
magnitude stronger than typical Coulombic inter-particle force and
result in a coupled motion of both nanoparticles characterized by a
pair of normal modes. We demonstrate cold damping of these normal
modes, either independently or simultaneously, to sub-Kelvin
temperatures at pressures of 5×10−3mbar. Experimental observations are
captured by a theoretical model that we use to survey the parameter
space more widely and to quantify the limits imposed by measurement
noise and time delays. Our work paves the way for the study of quantum
interactions between meso-scale particles and the exploration of
multiparticle entanglement in levitated optomechanical systems.
Funder
Grantová Agentura České
Republiky
Akademie Věd České
Republiky
Ministerstvo Školství, Mládeže a
Tělovýchovy
Subject
Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials