Demonstration of motion transduction based on parametrically coupled mechanical resonators.

Universal sensing of the motion of mechanical resonators with high precision and low backaction is of paramount importance in ultraweak signal detection, which plays a fundamental role in modern physics. Here we present a universal scheme that mechanically transfers the motion of the resonator not directly measurable to the one that can be precisely measured using mechanical frequency conversion. Demonstration of the scheme at room temperature shows that both the motion imprecision and the backaction force are below the intrinsic level of the objective resonator, which agrees well with our theoretical prediction. The scheme developed here provides an effective interface between an arbitrary mechanical resonator and a high quantum efficient displacement sensor, and is expected to find extensive applications in highly demanding mechanical-based force measurements.