emcc · Quantum measurement and control of non-classical mechanical states

Mechanical systems are an essential platform for future quantum science and technologies, such as quantum interfaces, sensors and transducers, and for studies of macroscopic quantum physics. The ability to measure and control macroscopic non-classical states is an outstanding challenge. The aim of the proposed research is to obtain the motional non-classical states of a macroscopic mechanical oscillator using quantum measurement and control techniques. The first non-classical state here is a single-phonon Fock state which will be generated by controlling the phonons at a single quantum level. This single-phonon state will be heralded by single photon detection, verified using photon counting statistics, and further reconstructed using state tomography which can completely reveal the non-classicality of the state. The second non-classical state is a squeezed state where either the position or momentum is localized with better precision than the zero-point motion. Achieving the measurement-based preparation of squeezed states requires the usage of quantum measurement techniques, in my case, continuous position measurements with a speed faster than the rate at which noise couples into the position from the momentum.The experimental demonstrations of the two non-classical states will be performed on millimetre-sized macroscopic membranes with exceptionally high coherence, and even, at temperatures much higher than previous experiments of non-classical nanomechanical oscillators. This will greatly relax the requirements of quantum experiments with macroscopic mechanical systems, and potentially enables new quantum technology at room temperature. The project will pave the way towards advanced quantum state engineering by quantum measurement and control of mechanical motion, building new high-performance quantum devices, and developing and testing potentially transformational new ideas for quantum gravitational decoherence tests and ultraprecise sensing.