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Abstract:
Optical quantum-limited displacement measurements play a key role in experimental tests of gravity, electromagnetism, and quantum mechanics. Originally explored in the context of interferometric gravitational wave detectors, they more recently have been explored for optomechanical sensing and protocols for quantum state preparation of mechanical motion. In an optical quantum-limited displacement measurement, photon shot noise creates fluctuations that mask mechanical motion (imprecision noise) and imparts a fluctuating force on the mechanical oscillator (radiation pressure backaction). Operating in the backaction-dominated regime is a prerequisite to realize ponderomotive squeezing and ground state cooling, and thus is a key motivation for the development of high-quality factor (Q) nanomechanical oscillators in the field of quantum optomechanics.
In this dissertation, we chronicle our efforts to observe radiation pressure backaction with high-stress silicon nitride (Si3N4) nanomechanical oscillators at room temperature. The high-Q trampoline and nanoribbon resonators we employ offer a promising platform to observe radiation pressure backaction because of their low thermal noise. As such, we use them to explore the limits of free space and cavity-enhanced interferometers and optical levers. Additionally, we investigate active imaging of a mechanical oscillator, and in the process generalize radiation pressure backaction to an arbitrary mechanical mode, demonstrating it arises from photon shot noise in both time and space.