Abstract: A Josephson quantizer is driven by a sinusoidal microwave generator whose output is combined with a digital two-level code representing a desired waveform. The result is to produce a bipolar drive signal of increased frequency and a bipolar Josephson output with voltage increased significantly. Output voltage is developed according to the relationship V=Nnmfs/KJ, where N is the number of junctions, n is the Josephson junction constant voltage step number, fs is the sampling frequency, m is an integer multiple of the sampling frequency and is ≧2, and KJ is the Josephson constant. The digital code generator receives the output of an improved modulator which incorporates a three-level to two-level transformation on the output of a standard three-level modulator in one embodiment. In a second embodiment, a modified two-level modulator produces a bit sequence where the polarity of the next bit is allowed to change only if there is an odd number of consecutive bits of the same polarity.

Abstract: A superconducting integrated circuit that uses a digital input to rapidly select any one of several thousand quantized output voltages. The voltages are generated directly by microwave synchronized Josephson junctions and are as accurate as the externally generated microwave frequency. The circuit makes possible fast voltage comparisons and the digital synthesis of ultra-accurate ac waveforms whose amplitude derives directly from the internationally accepted definition of the volt.