A quantum flux parametron (QFP) 12-bit shift register capable of stable microwave frequency operation

A 12-bit shift register employing the quantum flux parametron (QFP) as its basic element is presented. The 12-bit shift register operates at frequencies from dc up to 4.24 GHz with an on-chip total power consumption below 10 nW. Such a low power consumption is possible to obtain because (1) the QFP has very little power dissipation and (2) the clock lines do not dissipate power. The clock current is applied as a standing wave and is distributed by inductive division. The output waveform has been sampled in the time domain at a clock frequency of 2.4 GHz in spite of the low output signal amplitude (about 10 µV) and of the large crosstalk with the clock frequency. The 12-bit shift register is capable of stable operation, demonstrating that at least 10 15 error-free operations per QFP are possible.