Quantum-Assisted inertial sensors through Confocal Optical Levitation of nAnopartiCles – QACOLAC

Through the measurement of dynamical motions, inertial sensors lay at the core of multiple civilian and military applications, such as autonomous navigation (i.e., GPS-free). Project QACOLAC offers to develop a new technology of optomechanical inertial sensors of high performance, which relies on the optical levitation of nanoparticles in vacuum. Optical levitation is an emerging research topic, in which extremely resonant mechanical oscillators are assembled using optical forces. Commonly, such devices are achieved through an optical tweezer that traps and levitates a nano-object inside a vacuum chamber. Optically confined, the nanoparticle then behaves like an oscillator that, being strongly decoupled from its environment, can reach extreme quality factors at low pressure (beyond hundreds of billions).

Thanks to the quality of their resonances, levitated systems are currently the subject of numerous studies aiming to display quantum phenomena at the mesoscopic scale, with both fundamental and applied perspectives. In particular, in metrology these devices allow for the conception of inertial sensors. By switching off the optical trap and monitoring the free fall of a nanoparticle subjected to an external force, one can perform acceleration measurements on a short timescale (i.e., with a large bandwidth). Unfortunately, these free-fall devices suffer from low precision, preventing their deployment for applications such as autonomous navigation.

By harnessing a new levitation scheme, QACOLAC aims to develop large-bandwidth, precise, and chip-integrable free-fall-based inertial sensors. The project relies on a so-called confocal trapping architecture—in which nano-objects are levitated using two confocal laser beams forming a standing wave. Extremely sensitive to optical aberrations, the design of this trap stands as a technological challenge that will be overcome here using adaptive-optics methods providing an extreme degree of correction. With respect to traditional optical tweezers, a confocal architecture will significantly improve optomechanical confinement and free-fall duration, which will be leveraged to design compact, large-bandwidth inertial sensors with high sensitivity. Furthermore, quantum measurement protocols will be implemented to further enhance the device's performance.