Control and measurement of magnetic fluxoid quanta for small force standard

• Speaker: Choi, Jae-Hyuk (Division of Physical Metrology, Korea Research Institute of Standards and Science, Korea)

In absence of force standard established in the range below a micro-newton, our research driven toward a quantum-based force standard is introduced. Exploring candidates which provide force units identical and stable intrinsically, and useful in applications, we suggested a hybrid system of a superconducting micro-annulus with multiple-quantum states and a mechanical spring in classical regime combined: the magnetic moment of the annulus proportional to the quantum number generates force in magnetic-field gradient. With an ultrathin silicon nitride cantilever with an 8 m-diameter Nb annulus on, the magnetic moment due to a single fluxoid quantum was precisely determined using a lab-built attonewton-sensitivity cantilever magnetometer. In this talk, we present a scheme to control the number of fluxoid quanta by designed magnetic and thermal cycles, and preliminary results in small-force realization in a sub-piconewton range as well as the construction of a low-temperature realization setup.