Passive On-Chip Superconducting Circulator Using a Ring of Tunnel Junctions.

Area of Science:

• Solid State Physics
• Quantum Electronics
• Microwave Engineering

Background:

• Microwave circulators are essential components in microwave systems for signal routing and isolation.
• On-chip integration of passive circulators remains a challenge due to size and performance limitations.
• Superconducting devices offer potential for compact and high-performance circulator designs.

Purpose of the Study:

• To design and investigate a passive, on-chip microwave circulator.
• To explore two physical realizations: Josephson junctions (JJs) and quantum phase slip elements (QPS).
• To demonstrate high isolation, robustness, and significant bandwidth for the proposed circulator.

Main Methods:

• Design of a ring structure incorporating superconducting tunnel junctions (JJs or QPS).
• Capacitive coupling for JJ-based circulator and inductive coupling for QPS-based circulator.
• Application of a constant bias to the ring's center for symmetry breaking, eliminating the need for external microwave or RF bias.

Main Results:

• Achieved high isolation and robustness against fabrication imperfections and bias fluctuations.
• Demonstrated a bandwidth exceeding 500 MHz with realistic device parameters.
• Verified the effectiveness of the passive, on-chip design for both JJ and QPS implementations.

Conclusions:

• The proposed passive, on-chip microwave circulator design is feasible and offers significant advantages.
• Superconducting tunnel junctions provide a viable platform for high-performance microwave circulators.
• The design's robustness and bandwidth make it suitable for advanced microwave and quantum applications.