Results of capacitance ratio measurement for the single electron pump-capacitor charging experiment

We report on a metrological application of the single electron tunneling (SET) phenomena: a precise measurement of the ratio of two cryogenic capacitors. Our measurement used a superconducting SET electrometer as the null detector for a capacitance bridge. We have achieved a 3-ppm level of imprecision in the measurement of capacitance ratio from 100 to 1000 Hz. We used custom-made cryogenic vacuum-gap capacitors, which have a leakage resistance of no less than 10/sup 19/ /spl Omega/. Further improvements can be made in the attempt to obtain an imprecision of 10/sup -8/ at lower frequencies, sufficient for the metrological measurement of capacitance or the fine-structure constant using an SET pump.