Tunable Coupling Architecture for Fixed-Frequency Transmon Superconducting Qubits.

Area of Science:

• Quantum Computing
• Superconducting Qubits
• Quantum Error Correction

Background:

• High-fidelity two-qubit operations are essential for scalable quantum error correction.
• Tunable buses in superconducting qubits offer higher gate fidelities but can introduce leakage.
• Fixed-frequency qubits are a common architecture, but improving their gate speeds is challenging.

Purpose of the Study:

• To present a modified tunable bus architecture for fixed-frequency superconducting qubits.
• To reduce adiabaticity restrictions for faster gate operations.
• To mitigate leakage pathways introduced by tunable buses.

Main Methods:

• Designed and implemented a modified tunable bus coupler.
• Characterized the coupler's performance on various two-qubit superconducting devices.
• Assessed gate fidelity and calibration stability.

Main Results:

• Achieved a maximum two-qubit gate fidelity of 99.85%.
• Demonstrated reduced adiabaticity restrictions, enabling faster gate operations.
• Showed that the coupler calibration remained stable for at least one day.

Conclusions:

• The modified tunable bus architecture is effective for high-fidelity two-qubit gates in fixed-frequency superconducting qubits.
• This approach enhances scalability for quantum error correction.
• The demonstrated stability suggests practical applicability in quantum computing systems.