Linear cooling of a levitated micromagnetic cylinder by vibration

TL;DR

This paper demonstrates feedback cooling of a levitated micromagnetic cylinder's translational and librational modes using a piezoelectric actuator and superconducting detection, achieving millikelvin temperatures and suggesting pathways toward ground state cooling.

Contribution

The study introduces a linear feedback cooling method for a levitated micromagnet, achieving significant temperature reduction and high Q-factors, with prospects for ground state cooling.

Findings

Center-of-mass mode cooled to ~7 K

Librational mode cooled to 830 ± 200 mK

Q-factor of 1.0 × 10^7 for the center-of-mass mode

Abstract

We report feedback cooling of translational and librational degrees of freedom of a levitated micromagnet cylinder, utilizing a piezoelectric actuator to apply linear feedback to high-Q mechanical modes. The normal modes are measured with a superconducting pick-up coil coupled to a DC SQUID, and phase information is fed back to the piezoelectric actuator to feedback cool a center-of-mass mode to $\sim$7 K, and a librational mode to $830 \pm 200$ mK. Q-factors of $1.0 \times 10^7$ are evaluated for the center-of-mass mode. We find that it is plausible to achieve ground state cooling of the center-of-mass mode by introducing vibration isolation, optimizing the geometry of the pick-up coil to focus on the specific mode of interest and utilizing a state-of-the-art SQUID for detection.