Room-temperature quantum optomechanics using engineered mechanical resonators

At room temperature, quantum optomechanical phenomena have only been observed in pioneering experiments using levitated nanoparticles and optically-trapped cantilevers where an optical restoring force controls the oscillator stiffness. Recent advances in engineered mechanical resonators, where the restoring force is provided by material rigidity rather than an external optical potential, have realized ultra-high quality factors (Q) by exploiting`soft clamping', achieving more than 100 quantum coherent oscillations at room temperature. In this talk, I will explain how we recently reached the quantum regime of cavity optomechanics at room temperature using engineered mechanical resonators in a ``membrane-in-the-middle'' system. I will discuss various other physical processes that emerge in this parameter regime, and the techniques we developed to mitigate these effects, which led to the demonstration of 1.09-dB ponderomotive squeezing and single-quantum conditional thermal coherent states.