Picosecond applications of Josephson junctions

The behavior of simple superconducting circuits in the picosecond regime is described in a comprehensive way, with primary emphasis being given to the step function and pulse responses of these circuits. Topics receiving detailed discussion include Josephson-junction modeling with both the microscopic and shunted-junction models. Limitations of the shunted-junction model are explored by comparing it with experimental results and with the microscopic model. An approximate evaluation is given of the important dynamical properties of junctions made with the dominant fabrication technology (Pb-alloy systems), as a function of tunneling barrier thickness. Rounding out the device aspects of the discussion, we describe in detail the properties of superconducting microstrip transmission lines, with an emphasis on their high-speed behavior. Turning to simple circuits we review experimental results on the measurement of picosecond regime transient signals. The concept of turn-on delay is analyzed anew, providing simplified and extended results. Details of concepts for pulse height and pulsewidth measurements are explored, leading to the conclusion that the time resolution of superconducting circuits is limited to approximately the period of one plasma oscillation. With present Pb-alloy fabrication technology this limit is 2 ps.