High-fidelity gates in a single josephson qubit

Area of Science:

• Quantum Computing
• Superconducting Circuits
• Quantum Error Measurement

Background:

• Superconducting qubits are a leading platform for quantum computation.
• Accurate characterization of errors is crucial for improving qubit performance.
• Existing methods may not fully distinguish between different error sources.

Purpose of the Study:

• To develop novel experimental procedures for precise error measurement in superconducting qubits.
• To establish a comprehensive error budget by separating gate and measurement errors.
• To validate the integrity of the quantum system within the qubit manifold during operations.

Main Methods:

• Implementation of new experimental techniques for error quantification.
• Separation of gate errors from measurement errors for detailed analysis.
• Utilizing a Ramsey interference error filter for high-sensitivity measurements.

Main Results:

• Demonstrated single-qubit gate fidelities of 0.98, primarily limited by energy relaxation.
• Constructed a complete error budget for the superconducting qubit system.
• Measured occupation probabilities outside the computational basis down to 10^-4, confirming system integrity.

Conclusions:

• The developed methods enable accurate characterization of superconducting qubit errors.
• High gate fidelities are achievable, with energy relaxation identified as a key limitation.
• The quantum system reliably operates within the intended qubit manifold, crucial for fault-tolerant quantum computing.