Quantum-noise-limited microwave amplification using a graphene Josephson junction.

Area of Science:

• Quantum Information Science
• Condensed Matter Physics
• Materials Science

Background:

• Josephson junctions (JJs) are crucial for superconducting qubits and amplifiers, forming key components in quantum information processing.
• Josephson parametric amplifiers (JPAs) are widely used for low-noise amplification of microwave signals in quantum circuits.
• Existing JPAs utilize Al-AlOx-Al tunnel junctions tuned by magnetic flux, limiting tunability options.

Purpose of the Study:

• To implement a quantum-noise-limited Josephson parametric amplifier (JPA) using a two-dimensional (2D) van der Waals material.
• To demonstrate gate tunability of the JPA properties, offering an alternative to magnetic flux tuning.
• To explore the potential of graphene-based JJs for advanced quantum information processing and sensing applications.

Main Methods:

• Fabrication of a JPA utilizing a graphene Josephson junction (JJ).
• Characterization of the JPA's amplification performance, including gain, bandwidth, and saturation power.
• Investigation of the gate tunability of the JPA's resonance frequency.

Main Results:

• Successful implementation of a quantum-noise-limited JPA based on a graphene JJ.
• Demonstrated linear resonance gate tunability of 3.5 GHz.
• Achieved 24 dB amplification with a 10 MHz bandwidth and -130 dBm saturation power, comparable to state-of-the-art JPAs.
• Operation in the quantum-limited noise regime confirmed.

Conclusions:

• The developed gate-tunable JPA represents a significant advancement for sensitive signal processing in quantum circuits.
• Graphene JJs offer a promising platform for 2D van der Waals quantum electrodynamics architectures.
• The device has potential applications in novel microwave bolometers and scalable integrated quantum systems.