Cavity cooling of free silicon nanoparticles in high-vacuum

TL;DR

This paper demonstrates cavity cooling of silicon nanoparticles in high vacuum, significantly reducing their transverse kinetic energy, which advances the potential for testing quantum mechanics with mesoscopic objects.

Contribution

It presents the first experimental realization of cavity cooling for silicon nanoparticles in high vacuum, using a high-finesse infrared cavity to reduce their kinetic energy.

Findings

Transverse kinetic energy reduced by over a factor of 30.

Silicon nanoparticles launched with velocities below 1 m/s.

Successful cavity cooling in a high-vacuum environment.

Abstract

Laser cooling has given a boost to atomic physics throughout the last thirty years since it allows one to prepare atoms in motional states which can only be described by quantum mechanics. Most methods, such as Doppler cooling, polarization gradient cooling or sub-recoil laser cooling rely, however, on a near-resonant and cyclic coupling between laser light and well-defined internal states. Although this feat has recently even been achieved for diatomic molecules, it is very hard for mesoscopic particles. It has been proposed that an external cavity may compensate for the lack of internal cycling transitions in dielectric objects and it may thus provide assistance in the cooling of their centre of mass state. Here, we demonstrate cavity cooling of the transverse kinetic energy of silicon nanoparticles propagating in genuine high-vacuum (< 10^8 mbar). We create and launch them with longitudinal velocities even down to v < 1 m/s using laser induced thermomechanical stress on a pristine silicon wafer. The interaction with the light of a high-finesse infrared cavity reduces their transverse kinetic energy by more than a factor of 30. This is an important step towards new tests of recent proposals to explore the still speculative non-linearities of quantum mechanics with objects in the mass range between 10^7 and 10^10 amu.