Low-Voltage Bit-Serial Single-Flux-Quantum Microprocessor for Integrating Memories

We report an energy-efficient bit-serial microprocessor based on single-flux-quantum (SFQ) logic, called CORE e3, using a low-voltage bias technique. This microprocessor was designed for integrating memories, and we developed it to investigate the efficient use of hardware and energy, using the low-voltage rapid single-flux-quantum (LV-RSFQ) technique. We implemented the CORE e3 and its test circuit using a 10-kA/cm² Nb process. We confirmed via logic simulations that all instructions were executed correctly with a 1-GHz system clock. We expect a 3.51 fold improvement in energy efficiency.