Syndrome-Resolved Decoding of Qubit Readout Errors

Abstract:Readout errors in superconducting qubits include incorrect state assignment, bit flips within the computational subspace, and leakage to non-computational states. These errors require different mitigation strategies, yet conventional measurement fidelity and repeatability metrics do not resolve their individual contributions. Previous repeated-readout studies have shown that temporal correlations reveal additional information about readout errors. Here we introduce the Readout Error Decoder (RED), which converts repeated thresholded binary records into a channel-resolved error budget. Controlled error injections validate the channel-specific response of the decoder. We demonstrate RED on both fluxonium and transmon qubits and across distinct leakage-lifetime regimes. RED identifies the error channels limiting readout performance without requiring dedicated discrimination of non-computational states, providing a basis for targeted readout optimization across different qubit modalities.

arXiv:2610.20810 [quant-ph]

(or arXiv:2610.20810v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.20810 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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