Levitation by Quantum Feedback Control

The control of levitated mesoscopic objects has developed into a flourishing field promising significant advances in sensing technologies, stochastic and quantum thermodynamics as well as macroscopic quantum physics. While optical levitation has already reached operation in the quantum regime, internal heating by absorption is a major challenge. With FLIP (Feedback Levitation on an Inverted Potential) we propose an original solution: dark field optical detection plus active feedback control provides position stabilization (without additional confining potential) and cooling to a close-to-pure quantum state without absorption. If successful, FLIP will go beyond the state of the art in several ways. It provides access to quantum control of absorbing objects in high vacuum (e.g. spin mechanics with NV-centers). It opens the door to large quantum superpositions via free-fall experiments with internally cold particles. All the more since it results in near-pure quantum states outside the usual harmonic oscillator framework for which the trapping characteristics (ruled by the feedback strength) and the optical detection can be controlled independently. Finally, it enables sensing with unstable potentials in the quantum regime. Following the recent demonstration of quantum limited position readout, real-time state reconstruction and feedback cooling to the ground state, it is the ideal time to develop levitation in the dark optical field.