Gate-Tunable Spectrum and Charge Dispersion Mitigation in a Graphene Superconducting Qubit.

Area of Science:

• Quantum Computing
• Condensed Matter Physics
• Materials Science

Background:

• Controlling quantum-coherent superconducting circuits is key for high-performance qubits.
• Traditional methods adjust circuit geometry or use magnetic fields for in-situ control.
• Semiconductor-weak-link Josephson junctions offer electric-field tunability, an advancement over traditional methods.

Purpose of the Study:

• To demonstrate large gate tunability of qubit properties in a graphene superconducting circuit.
• To investigate the impact of graphene-based Josephson junctions on qubit frequency, anharmonicity, and charge dispersion.
• To rationalize the observed tunability using a theoretical model.

Main Methods:

• Fabrication of a graphene superconducting circuit incorporating gate-tunable Josephson junctions.
• Characterization of qubit properties including frequency, anharmonicity, and charge dispersion.
• Theoretical modeling of Cooper pair transmission through Andreev bound states.

Main Results:

• Achieved significant gate tunability of qubit frequency, anharmonicity, and charge dispersion in graphene circuits.
• Demonstrated that high Cooper pair transmission in graphene weak links suppresses charge dispersion.
• Validated the model explaining qubit property control via Andreev bound states.

Conclusions:

• Graphene superconducting circuits provide versatile, gate-tunable building blocks for advanced quantum circuits.
• Electric-field control offers a promising avenue for designing and optimizing superconducting qubits.
• The suppression of charge dispersion in graphene qubits enhances their performance potential.