Abstract
No experiment today provides evidence that gravity requires a quantum description. The quantum optical control of solid-state mechanical devices, quantum optomechanics, may change that situation -- by enabling experiments that directly probe the phenomenology of quantum states of gravitational source masses. Such "quantum Cavendish" experiments require to explore extreme regimes of both quantum and gravity phenomena, specifically: delocalized motional quantum states of sufficiently massive objects, as well as gravity experiments on the microscopic scale. Extending quantum optomechanics methods to trapped solids offers a unique approach for pushing into these ambitious parameter regimes. I review the current status in the lab and the challenges to be overcome for future experiments.
