High-speed Josephson processor technology

High-speed operation of Josephson processors is demonstrated. They are a 4-b microprocessor, a 4-b processor, and an 8-b digital signal processor. Key technologies to realize these circuits are described from the viewpoint of circuit design. The technologies are a high-speed logic gate, named MVTL (modified variable threshold logic), and a three-phase sinusoidal power supply system. The MVTL gate has a large operating margin and high sensitivity. The MVTL gate family consists of OR, AND, 2/3 majority (MJ), and timed inverter (TI). Using these gates a variety of processors have been designed. These processors operate with three-phase power. The waveform is sinusoidal with DC-offset. This power supply system needs no latch and regulator circuit. This makes the processor very simple, and thus results in high-speed operation. To fabricate these processors, niobium junctions are very important, because they are reliable, uniform, controllable, and reproducible. High-speed gates, three-phase power supplies, and niobium junctions are indispensable for high-speed Josephson processors.