Ultrafast Meissner-levitated microrotor

Levitated mechanical systems offer a powerful and flexible platform for the realization of ultralow-noise sensors and tests of fundamental physics. Here, we report the demonstration of a levitated microrotor, consisting of a magnetic microsphere levitated by the Meissner effect at 4.2 kelvin. The rotor reaches rotation frequencies above 2.3 megahertz (138 million revolutions per minute) while exhibiting an exceptionally low damping rate of 4.75 × 10^-7 hertz. Exploiting the linear dependence of friction on the gas density, we demonstrate high-accuracy absolute pressure sensing over a wide range at cryogenic temperature. Last, we detect the thermal torque noise at intermediate pressure by operating the rotor in synchronized mode, resulting in a first preliminary narrowband search for axion-like dark matter. More broadly, the combination of high rotational speed, low temperature, and low thermal torque noise establishes a previously unidentified regime for precision measurements, with direct implications for the detection of extremely weak forces and fields.