Nanoscale feedback control of six degrees of freedom of a near-sphere

TL;DR

This paper demonstrates comprehensive feedback cooling of all six degrees of freedom of a near-spherical nanoparticle, achieving near-ground state cooling for translational and angular motions, enabling advanced nanoparticle control and sensing.

Contribution

It introduces a method for feedback cooling of all six degrees of freedom of a nanoparticle, including angular motions, with high precision and low temperatures, advancing nanoparticle manipulation techniques.

Findings

Achieved translational occupation numbers of 6 ± 1, 6 ± 1, and 0.69 ± 0.18.

Realized feedback cooling of angular motions to below 0.03 K.

Developed a thermometry method for three angular oscillations.

Abstract

We demonstrate feedback cooling of all the angular motions of a near-spherical neutral nanoparticle with all the translational motions feedback-cooled to near the ground state. The occupation numbers of the three translational motions are $6 \pm 1$, $6 \pm 1$, and $0.69 \pm 0.18$. A tight, anisotropic optical confinement allows us to clearly observe three angular oscillations and to identify the ratio of two radii to the longest radius with a precision of $\unit[0.09]{\%}$. We develop a thermometry for three angular oscillations and realize feedback cooling of them to temperatures of lower than $\unit[0.03]{K}$ by electrically controlling the electric dipole moment of the nanoparticle. Our work not only paves the way to precisely characterize trapped nanoparticles, but also forms the basis of utilizing them for acceleration sensing and for exploring quantum mechanical behaviors with both their translational and rotational degrees of freedom.