Sub-Kelvin Feedback Cooling and Heating Dynamics of an Optically Levitated Librator

Rotational optomechanics strives to gain quantum control over mechanical rotors by harnessing the interaction of light and matter. We optically trap a dielectric nanodumbbell in a linearly polarized laser field, where the dumbbell represents a nanomechanical librator. Using measurement-based parametric feedback control in high vacuum, we cool this librator from room temperature to 240 mK and investigate its heating dynamics when released from feedback. We exclude collisions with residual gas molecules as well as classical laser noise as sources of heating. Our findings indicate that we observe the torque fluctuations arising from the zero-point fluctuations of the electromagnetic field.

Automated summary

Rotational optomechanics aims to control mechanical rotors at the quantum level by utilizing the interaction between light and matter. In this study, a dielectric nanodumbbell representing a nanomechanical librator is optically trapped in a linearly polarized laser field and cooled to 240 mK using measurement-based parametric feedback control in high vacuum. Torque fluctuations arising from the zero-point fluctuations of the electromagnetic field are observed as a source of heating dynamics.