Motional Quantum Ground State of a Levitated Nanoparticle from Room Temperature

TL;DR

This paper demonstrates quantum ground state cooling of a levitated nanoparticle at room temperature using optical cavity techniques, achieving a low phonon number and high coherence, paving the way for advanced macroscopic quantum experiments.

Contribution

The authors achieve room-temperature quantum ground state cooling of a levitated nanoparticle using coherent scattering into an optical cavity, a significant advancement in optomechanics.

Findings

Nanoparticle cooled to 0.43 phonons at room temperature.

Achieved a coherence time of 7.6 microseconds.

System operates in the strong cooperativity regime.

Abstract

We report quantum ground state cooling of a levitated nanoparticle in a room temperature environment. Using coherent scattering into an optical cavity we cool the center of mass motion of a $143$ nm diameter silica particle by more than $7$ orders of magnitude to $n_x=0.43\pm0.03$ phonons along the cavity axis, corresponding to a temperature of $12~\mu$K. We infer a heating rate of $\Gamma_x/2\pi = 21\pm 3$ kHz, which results in a coherence time of $7.6~\mu$s -- or $15$ coherent oscillations -- while the particle is optically trapped at a pressure of $10^{-6}$ mbar. The inferred optomechanical coupling rate of $g_x/2\pi = 71$ kHz places the system well into the regime of strong cooperativity ($C \approx 5$). We expect that a combination of ultra-high vacuum with free-fall dynamics will allow to further expand the spatio-temporal coherence of such nanoparticles by several orders of magnitude, thereby opening up new opportunities for macrosopic quantum experiments.