Supercurrent graduate in units of 2 ef

The supercurrent in the I-V characteristics of superconducting granular tin films are graduated in units of 2 ef , in the presence of microwave fields with f=8-12 GHz, to an accuracy of 200 p.p.m. This is interpreted in terms of the Bloch oscillations, which are demonstrated to be dual to the Josephson oscillations. When the measurement is carried out at extremely low temperatures using arrays of small Josephson junctions with well-controlled junction parameters, the accuracy can be improved by 3-4 orders of magnitude. Then it becomes possible to examine the consistency of three macroscopic quantum relations: nf=I/2e , V=mhf/2, and V/I=h/ ie², where n, m, and i are integers