Bloch oscillations in small Josephson junctions: Possible fundamental standard of dc current and other applications

Possible applications of the quantum "Bloch" oscillations of the frequency in Josephson junctions with very small capacitance are discussed. The most natural application of this effect could be a fundamental standard of the dc current: I= 2efm, where f is an external radiation frequency and m is an integer. Of the other applications, a possibility to develop a sub-picowatt superconducting transistor seems the most attractive. Analog properties of the small junctions and prospects of their use in microwave receivers are also discussed briefly. Conditions of experimental observation and practical applications of the Bloch oscillations are formulated and the main apparent problems are outlined.