Conditional Mechanical Squeezing of a Micromechanical Oscillator Approaching the Quantum Regime

Abstract

Optomechanics is a rapidly developing field studying systems with optical and mechanical resonators coupled via radiation pressure. This coupling plays a key role in precision displacement and momentum sensing like in gravitational wave detection and atomic force microscopy. Recently the field has entered the quantum regime, with the interaction being used to prepare pondermotively squeezed states of light, optical-optical entanglement, motional ground states, and more.

In this thesis, I will introduce and demonstrate a conditionally-prepared motional squeezed state of a micromechanical oscillator approaching the quantum regime, with a conditional position and momentum variance of 11.93 and 6.32 times the zero point fluctuation respectively. This work was done by performing fast, continuous measurement of the position of a 50 ng oscillator in a detuned optomechanical cavity and applying optimal filtering, namely the Wiener filter, to the noisy measurement record to estimate the conditional state.

I also present a new technique for locking homodyne detectors using a free-space continuously tunable optical field modulator, enabling rapid tomographic measurements of optical states. Lastly, I also include an appendix detailing a method for reducing seismic Newtonian noise of next generation gravitational wave detectors like Cosmic Explorer utilizing simple earthworks, inspired by phononic meta-materials of contemporary optomechanics research groups.