A single-atom mechano-optical transducer for sensing sub-attonewton vector DC force

Mechano-optical transducers are devices that convert a force or displacement signal to an optical one, enabling ultrasensitive mechanical detection. Currently, ultraweak DC force sensors with high spatial resolution are in high demand for the search of possible exotic spin-dependent interactions beyond the standard model in sub-millimeter scale. Here, we demonstrate a mechano-optical transducer of a single trapped ion with the force sensitivity about 600 [Formula: see text] for the DC force. This method utilizes the Doppler shift of the time-resolved fluorescence to detect the ion's micromotion that is coupled to a vector force. By alternating the directions of the detection laser beams, the vector DC forces can be precisely measured. Such a mechano-optical transducer provides sub-attonewton sensitivity with the spatial resolution in single-atom level, enabling various uses for both scientific and industrial purposes.