Optomechanical sensors live at the intersection of nanomechanical devices and quantum optical control. For the Quantum Sensing group, our main experimental sensing line consists of tiny glass particles (diameter of about 100 nm) which are levitated against gravity using optical (laser traps) or electrostatic (Paul traps) forces. A typical optical experimental layout (see figure) consists of a vacuum chamber, optical components and control electronics. For our investigations we use quantum optics techniques, such as homo-, heterodyne and lock-in detection, feedback control, or optical cavity coupling and read-out . Excellent system isolation, along with these techniques, enable us to push the performance limit of our sensors beyond the thermal noise limit into a regime where quantum mechanical effects (mesoscopic superposition states, squeezing, etc.) can be investigated and utilized. One example of pushing a rotational sensor into the quantum regime is our recent work with ETH Zurich . We introduced a mechanical nanorotor into a regime where its rotational motion is no longer limited by thermal noise, but by the quantum vacuum fluctuations of light.
 D. Windey, C. Gonzalez-Ballestero, P. Maurer, L. Novotny, O. Romero-Isart, and R. Reimann, Cavity-Based 3D cooling of a Levitated Nanoparticle via Coherent Scattering ,Phys. Rev. Lett. 122, 123601 (2019).
 F. van der Laan, R. Reimann, F. Tebbenjohanns, J. Vijayan, L. Novotny, and M. Frimmer, Observation of radiation torque shot noise on an optically levitated nanodumbbell, arXiv:2012.14231 (2020)