Overlap junctions for high coherence superconducting qubits

Area of Science:

• Quantum computing
• Superconducting electronics
• Materials science

Background:

• High-coherence superconducting qubits are essential for quantum computing.
• Fabricating sub-micron Josephson junctions with high yield and coherence remains a challenge.
• Existing methods often rely on angle-dependent shadow masks, limiting scalability.

Purpose of the Study:

• To demonstrate the fabrication of sub-micron Josephson junctions using standard processing techniques.
• To investigate the impact of in situ Ar milling on aluminum surfaces for junction formation.
• To achieve high coherence in Josephson junctions for superconducting qubits.

Main Methods:

• Utilized two-step lithography with normal-angle evaporation.
• Employed in situ Argon (Ar) milling for cleaning aluminum surfaces prior to oxidation.
• Defined top and bottom electrodes using electron-beam lithography and an additive process.

Main Results:

• Successfully fabricated sub-micron Josephson junctions.
• Achieved high coherence in junctions formed on Ar-milled aluminum surfaces.
• Eliminated the need for angle-dependent shadow masks, simplifying the process.
• Demonstrated compatibility with conventional CMOS processing for improved margins and yield.

Conclusions:

• In situ Ar milling of aluminum surfaces is a viable method for fabricating high-coherence Josephson junctions.
• This technique simplifies fabrication and is conducive to scalable manufacturing of superconducting qubits.
• The demonstrated approach supports the integration of advanced qubit fabrication with standard semiconductor processing.