This project investigates quantum limited measurement and control for sensing of gravity. The present focus is the study of mechanical resonators at various size scales aiming for a new class of ultra coherent, quantum-enhanced optomechanical gravity sensors as described in Pratt, et al, PHYSICAL REVIEW X 13, 011018 (2023). A primary goal is to develop a micro-optomechanical oscillator (a pendulum) whose frequency is modulated by gravity, sensitive to changes in the local acceleration of gravity at the level of 10 parts per billion. A secondary goal is to achieve ultra low-frequency (1 mHz), ultralow loss (Q>1 billion) mechanical resonators capable of cryogenic operation at or below the standard quantum limit for proposed experiments in quantum gravity. Research encompasses the micro and nanofabrication of test structures, modeling and measurement of all noise sources, development and execution of optical detection schemes, strain engineering of resonators, and coherent- or measurement based feedback control of the resonator dynamics for ground state cooling, or, using nonlinear feedback of the coherent state, for creation of  Rayleigh, or Van der Pol limit cycles.