Rapid single-flux-quantum and adiabatic quantum-flux-parametron cell libraries using a 1 kA/cm² niobium fabrication...

Area of Science:

• Superconducting electronics
• Quantum computing hardware
• Low-power integrated circuits

Background:

• Superconductor logic families offer low power dissipation, suitable for advanced computing.
• Specific applications like qubit interface circuits and stochastic electronics require Josephson junctions with low critical current (I_c).

Purpose of the Study:

• To develop a fabrication process for low I_c Josephson junctions.
• To create rapid single-flux-quantum (RSFQ) and adiabatic quantum-flux-parametron (AQFP) cell libraries using this new process.
• To enable low-power operation for qubit interface circuits and stochastic electronics.

Main Methods:

• Development of the AIST 1 kA cm^-2 Nb planarized process (1KP) with a minimum critical current of 10 µA.
• Creation of RSFQ and AQFP cell libraries compatible with the 1KP.
• Fabrication and testing of RSFQ and AQFP circuits at 4.2 K.

Main Results:

• The 1KP process facilitates the design of superconductor logic with significantly reduced critical currents.
• RSFQ logic power dissipation was reduced to 3.2% of conventional methods.
• AQFP circuits using 1KP required approximately 40% less supply current compared to conventional designs.

Conclusions:

• The 1KP process is effective for fabricating low I_c Josephson junctions.
• RSFQ and AQFP circuits built with 1KP demonstrate substantial power and current savings.
• These advancements position 1KP-based circuits for use in qubit interface and stochastic electronics.