Colloquium: Prof. Gordon Shaw, NIST

TITLE: Precision small mass and force metrology from the macroscale to single photon limits  ABSTRACT: Measurements of small mass and small force appear in many areas of science, and are used to probe phenomena from the interactions between atoms to the big bang. Although accuracy at these scales can be difficult to achieve, the impending redefinition of the International System of Units (SI) opens up some intriguing possibilities. Since mass and force metrology will no longer be tied to the gravitational force acting on the kilogram artifact, other physics can potentially be used realize standards for the newton and kilogram units. In this talk, I will explain a framework that allows a continuous scaling of force measurements from millinewtons to nanonewtons using electrostatics to realize force using SI electrical units, and from nanonewtons to femtonewtons using photon momentum exchange forces derived from an SI-traceable laser power measurement and a high-quality factor mesoscale mechanical oscillator. Further scaling of force should be possible, even to the regime where forces are calculated by counting the photons reflecting from a mechanical sensor, providing the possibility of a new quantized standard for mass and force measurement.