Demonstration of adiabatic quantum-flux-parametron logic using a 3-metal layer niobium process

This paper demonstrates superconductor adiabatic quantum-flux-parametron (AQFP) logic based on a 3-metal layer 60 μ A μ m −2 niobium process SIMIT Nb03. The proposed AQFP cells utilize a minimal number of metal layers (two layers for structuring and one layer as ground), providing advantages in layer efficiency when compared with previous designs. By adopting Josephson junctions with a high critical current of 100 μ A, the AQFP logics also exhibit improved output current amplitude without requiring additional components. The cell library, incorporating building blocks such as buffer, inverter, constant, and branch cells, is then realized using a minimalist design principle. Numerical simulations of an 8-stage buffer chain, a NAND gate, and a 3-to-8 decoder demonstrate correct functionality and wide operating margins. Experimental validation is provided through the fabrication and measurement of two fundamental circuits, which showcase proper logic operation under 4.2 K. The proposed AQFP cell library, achieved with fewer metal layers, demonstrates the design feasibility of AQFP relying on less intricate processes, which makes it a promising candidate for scalable superconductor circuits.