Acceleration sensing with magnetically levitated oscillators above a superconductor

We experimentally demonstrate the stable trapping of a permanent magnet sphere above a lead superconductor, at vacuum pressures of 4 x 10(-8) mbar. The levitating magnet behaves as a harmonic oscillator, with frequencies in the 4-31 Hz range detected, and shows promise to be an ultrasensitive acceleration sensor. We directly apply an acceleration to the magnet with a current carrying wire, which we use to measure a background noise of similar to 10(-10) m/root Hz at 30.75 Hz frequency. With current experimental parameters, we find an acceleration sensitivity of S-a(1/2) = 1.2 +/- 0.2 x 10(-10) g/root Hz, for a thermal noise limited system. By considering a 300 mK environment, at a background helium pressure of 1 x 10(-10) mbar, acceleration sensitivities of S-a(1/2) similar to 3 x 10(-15) g/root Hz could be possible with ideal conditions and vibration isolation. To feasibly measure with such a sensitivity, feedback cooling must be implemented. Published under license by AIP Publishing.