Low power high speed computing using rapid single flux quantum circuits

Nowadays, the need for the higher speed and lower power consuming computers lead to searching for alternative logics to CMOS technology. Recent advances in the field of superconductor logic technology and superconducting very large-scale integration (VLSI) circuit fabrication allows us to design complex rapid single flux quanta (RSFQ) circuits and structures with high number of Josephson junctions on one chip. These advances lead to developing logic circuits that consume power orders of magnitude less than MOSFETs and working at the relatively higher frequency.In this work, we have designed a 4-bit arithmetic logic unit (ALU) with bit-parallel architecture in rapid single flux quantum logic regime. The parallel architecture allows the simpler structure than Kogge-Stone while maintaining the good latency. The ALU was designed using standard cell library to be fabricated with STP2 standard (2.5 KA/cm2) process and have a latency of 620ps at the most critical path at 2.5 mV bias in 25 GHz clock frequency. The ALU consists of more than 9000 junctions and has 8 different operations including multiplication, add and subtract, and consumes about 2.4 mW of power. This logic unit was designed to be used as a coprocessor with external CMOS processors and be able to function with CMOS memories. To confirm the working of the ALU, first all the parts were separately fabricated and tested in 4K pulse-tube custom designed cryocooler. The cooler and package is modified to measure high bias circuits.