Static characteristics of Josephson interferometers

Anna Maria Cucolo, M. R. Saggese, G. Patern�

Michitada Morisue, K. Isaji, M. Kaneko

This paper describes the dynamic threshold characteristics of Josephson switching gates. When high speed input signals are applied to the Josephson logic gate, the threshold characteristics of the gate are not always in accord with the well-known static threshold curves. This is because the static threshold curves are affected by quantum flux change in Josephson junctions under the high speed operation. The dynamic threshold characteristics of two typical logic gates, one is the CIL gate and the other the interferometer, are described in detail.

Carlo Camerlingo, B. Ruggiero, M. Russo +1 more

R. Simons, W. Jutzi, H. Beha

Flux quantum states (FQS) of interferometers with up to ten equal Josephson point junctions are characterized in the phase and current plane. Their symmetry properties are derived. Simple formulas are given to design interferometers being equivalent to uniformly distributed Josephson junctions.

Sebastian Kempf

Ronald F. Broom, W. Kotyczka, A. Moser

Several models, both static and dynamic, for calculating the maximum dc Josephson current versus external magnetic field “characteristic” of tunnel junctions of various geometries are described. The static models have the advantage of short computation times; the dynamic models, although slower, yield additional information on circuit-switching times. The dependence of the characteristics on the junction shape is described. The accuracy of a one-dimensional approximation used in the models has been tested experimentally, and theoretically against a two-dimensional approximation. In both cases, the one-dimensional treatment yields quantitatively good agreement provided the inductance of the junction is included in the model. Junctions defined by an oxide “window” of sinusoidal shape (maximum and minimum width at the center and ends, respectively) have a characteristic in which the side lobes are almost completely suppressed. The characteristics of a wide variety of junction shapes, including interferometers having two or more junctions, have been accurately calculated, permitting the design of devices for specific purposes.