Binary Counters Using Adiabatic Quantum Flux Parametron Logic

Adiabatic quantum-flux-parametron (AQFP) logic is an energy-efficient superconductor logic family. In this article, we design binary counters, namely an up counter, a down counter, and an up/down counter, based on AQFP logic. These binary counters are T-flip-flop-based and count logic 1s in the input signal that is synchronized with excitation currents, which clock the counters. The internal state of a T flip-flop changes when the internal state of the previous T flip-flop changes from logic 1 to 0 and from logic 0 to 1 for the count-up and count-down operations, respectively. Each internal state of a T flip-flop is read out serially by a buffer chain coupled to the T flip-flops. We fabricate 4-bit up, down, and up/down counters using the AIST 10 kA/cm2 Nb high-speed standard process and demonstrate their correct operation at low frequency. This is the first demonstration of binary counters based on AQFP logic.