FABRICATION OF A JOSEPHSON JUNCTION GATED CLOCK WITH PICOSECOND RESOLUTION

TIME DIGITIZERS BASED ON SEMICONDUCTOR DEVICES ARE ULTIMATELY LIMITED IN RESOLUTION BY THE SWITCHING TIME OF THOSE DEVICES. JOSEPHSON JUNCTIONS CAN SWITCH IN ONE HUNDREDTH OF THE TIME REQUIRED BY SEMICONDUCTOR DEVICES. FABRICATION TECHNOLOGY FOR JOSEPHSON JUNCTION INTEGRATED CIRCUITS HAS PROGRESSED TO THE POINT THAT VERY LARGE SCALE INTEGRATED CIRCUITS SUCH AS MICROPROCESSORS HAVE BEEN SUCCESSFULLY MANUFACTURED. THOSE JOSEPHSON JUNCTION MICROPROCESSORS OPERATE WITH A 1 GHZ CLOCK RATE (MORE THAN 10 TIMES FASTER THAN THE EQUIVALENT CIRCUITS FABRICATED WITHGALLIUM ARSENIDE (GAAS) TECHNOLOGY) AND DISSIPATE ONLY 5 MW (MANY TIMES LESS THAN THE GAAS DEVICES). IT IS PLANNED IN PHASE I TO DETERMINE THE FEASIBILITY OF BUILDING A TIME DIGITIZER WITH PICOSECOND (PS) RESOLUTION USING JOSEPHSON JUNCTION DEVICES. A JOSEPHSON JUNCTION GATED CLOCK HAS BEENDESIGNED AT HEWLETT-PACKARD LABORATORIES. IN SIMULATION, THIS DESIGN HAS A RESOLUTION OF 15 PS WITH TIMING JITTER OF 0.1 PS. A TIMING INTERPOLATOR COULD BE USED IN CONJUNCTION WITH THE GATED CLOCK TO GIVE SUBPICOSECOND RESOLUTION. VARIOUS PORTIONS OF THESE DEVICES HAVE ALREADY BEEN FABRICATED AND SHOWN TO OPERATE CORRECTLY. IF THE ENTIRE CIRCUIT CAN BE BUILT SUCCESSFULLY, IT CAN SERVE AS THE BASISFOR AN ULTRA-HIGH-PERFORMANCE TIME DIGITIZER.