Abstract: Mechanical systems have recently attracted significant attention for their potential use in quantum information processing tasks, for example, as compact quantum memories or as transducers between different types of quantum systems. Early experiments included ground-state cooling of the mechanical motion and squeezing of the optical field. Recent advances have allowed to perform measurements which realize various mechanical quantum states.
Here, we would like to discuss experiments where we demonstrate non-classical behavior of mechanical motion by coupling a micro-fabricated acoustic resonator to single optical photons. Our approach is based on optomechanical crystals, which possess engineered mechanical resonances in the Gigahertz regime that can be addressed optically from the conventional telecom band. Our measurements show how these structures can be used as a mechanical quantum memory for photons, and we demonstrate non-classical correlations from the high-Q mechanical resonance and an optical interface over the full decay time of the mechanical mode. These results are a promising step towards using such devices for quantum information processing tasks and testing quantum physics with massive objects.