A logic circuit with spatially distributed josephson junctions

摘要

A distributed Josephson junction logic circuit is disclosed which includes a plurality of serially disposed Josephson junctions in a superconductive wire-over-groundplane environment wherein the latter is terminated at both ends in its characteristic impedance and energized at one end with a constant voltage source. In addition, at least one portion of the wire-over-groundplane transmission line, which is disposed in series with the junctions, is utilized as an output control and has the same steady state current flowing in it as the plurality of Josephson junctions. Utilizing such an arrangement, logic can be performed by means of multiple controls on a single junction as in terminated line logic or by means of several junctions, each with one or more independent controls, in series. The design is such that the switching of any one or more junctions to the voltage state causes a decrease in current from a level which represents a logical "1" to a lesser current which is representative of a logical "0". The resulting logic circuits may be latching or non-latching in character. When both ends of the distributed Josephson junction logic circuit are terminated in the characteristic impedance of the associated transmission line, inputs and outputs can be located at arbitrary points along the transmission line. The terminating resistors, returned at both ends of the line to points of low impedance to ground compared to the impedance of the terminating resistor, absorb transients originating on the power line or at any point along the transmission line. When any one or more of the inputs to such a circuit is a logical "1", at least one of the associated gates switches to the voltage state, reducing the output current to the logical "0" level. In a latching mode of operation, the circuit latches in that state until the gate current is momentarily quenched by reducing the power supply voltage. Thus, each stage normally inverts. The logic operation performed is a positive NOR, which is sufficient to implement any logical function. If desired, two or three controls can be used with some or all of the gates to perform such functions as inhibit, AND-OR-INVERT and majority and threshold logic. Logic circuits utilizing Josephson junctions operating at the gap which provide constant voltages are shown. In addition, circuit arrangements incorporating series-parallel powering circuits and the interconnection of logic circuits between more than one circuit arrangement are shown.