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Benchmarking the Readout of a Superconducting Qubit for Repeated Measurements
S Hazra1, W Dai1, T Connolly1
1Yale University, Yale University, Department of Applied Physics, New Haven, Connecticut 06520, USA and Yale Quantum Institute, New Haven, Connecticut 06520, USA.
Physical Review Letters
|March 28, 2025
Summary
Readout fidelity in superconducting qubits can hide leakage errors. A new method measures these errors independently, revealing significant leakage even with high fidelity, crucial for quantum error correction.
Area of Science:
- Quantum Computing
- Superconducting Circuits
- Quantum Information Science
Background:
- Superconducting qubit readout involves a speed-backaction trade-off.
- Readout fidelity, a common metric, may not capture all error sources.
- Leakage errors are critical for quantum error correction applications.
Purpose of the Study:
- To introduce a method for measuring readout-induced leakage rates.
- To highlight the limitations of readout fidelity as a sole performance indicator.
- To characterize readout performance in superconducting qubits considering leakage.
Main Methods:
- Developed a technique using a composite operation: randomized qubit flip followed by readout.
- Repeatedly executed this operation to quantify leakage.
- Applied the method to characterize superconducting qubit readouts with varying durations.
Main Results:
- Readout fidelity can exceed 99.5% while masking significant leakage errors.
- Measured leakage rates varied substantially, from 0.12% to 7.76%.
- Demonstrated that readout fidelity alone is insufficient for comprehensive error assessment.
Conclusions:
- Independent leakage characterization is essential for superconducting qubit readout.
- The proposed method provides a crucial metric for quantum error correction viability.
- Optimizing readout requires balancing fidelity and minimizing leakage errors.
