We have operated a 7-junction electron pump as an electron counter with an error per pumped electron of 15 parts in 109 and an average hold time of 600 s. The accuracy and hold time are sufficient to enable a new fundamental standard of capacitance. We compare the measured accuracy of the pump as a function of pumping speed and temperature with theoretical predictions based on a model which includes stray capacitance.

We have measured the current noise of silver thin-film resistors as a function of current and temperature and for resistor lengths of 7000, 100, 30, and 1 mm. As the resistor becomes shorter than the electron-phonon interaction length, the current noise for large current increases from a nearly current independent value to the interacting hot-electron value ͑ p 3͞4͒2eI. However, further reduction in length below the electron-electron interaction length decreases the noise to a value approaching the independent hot-electron value ͑1͞3͒2eI first predicted for mesoscopic resistors. [S0031-9007(96)00179-2]

We have measured the supercurrent flowing through a nonhysteretic, ultrasmall, voltage-biased Josephson junction. In contrast with experiments performed so far on hysteretic Josephson junctions, we find a supercurrent peak whose maximum I(s max) increases as the temperature T decreases. The asymptotic T = 0 value of I(s max) agrees with the junction Ambegaokar-Baratoff critical current, as predicted by theory.