Phononic quantum sensors
In this project, we will develop mechanical systems of unprecedented coherence under full optomechanical quantum control. At the same time, these systems provide a versatile and practical platform for force measurements and sensing. This novel and unique combination generates a host of opportunities in science and technology, ranging from fundamental tests of quantum decoherence and highly non-classical mechanical sensor states, to new kinds of mechanical quantum transducers.
These advances will be enabled by recent pioneering work of my group in the area of phononic engineering, that is, tailoring the phononic density of states in periodic geometries. In combination with state-of-the-art cryogenic refrigeration, we will achieve coherence times of mechanical quantum states at the level of one second, challenging existing models for mechanical state collapse. We will implement cavity-optomechanical interfaces to these systems which operate deeply in the quantum regime, and by themselves find applications as narrow, noiseless filters sought-after for gravity wave detectors. Furthermore, we will harness purely mechanical parametric interactions as a new resource. This allows noiseless gain immediately in the sensing device, and the preparation of highly nonclassical sensor states, such as strongly squeezed and entangled states. To demonstrate the sensing capabilities of this platform, we will functionalize it magnetically, and perform real-time measurements of single electron spins. We will resolve the split of the mechanical wavefunction as it interacts with a spin in a superposition state, and eventually prepare mechanical Schrödinger cat states, never generated before with a massive, millimetre-sized object visible to the naked eye. At a practical level, this project catalyses the experimental convergence of spin sensing and quantum optomechanics, with synergistic effects both for magnetic resonance imaging at the molecular scale and spin-based quantum networks.