We develop a theory for two quasiparticle-induced decoherence mechanisms of a driven superconducting qubit. In the first mechanism, an existing quasiparticle (QP) tunnels across the qubit's Josephson junction while simultaneously absorbing a qubit excitation and one (or several) photons from the drive. In the second mechanism, a qubit transition occurs during the non-linear absorption process converting multiple drive quanta into a pair of new QPs. Both mechanisms can remain significant in gap engineered qubits whose coherence is insensitive to QPs without the drive. Our theory establishes a fundamental limitation on fidelity of the microwave qubit operations, such as readout and gates, stemming from QPs.
@article{arxiv.2505.00769,
title = {Quasiparticle-induced decoherence of a driven superconducting qubit},
author = {Mykola Kishmar and Pavel D. Kurilovich and Andrey Klots and Thomas Connolly and Igor L. Aleiner and Vladislav D. Kurilovich},
journal= {arXiv preprint arXiv:2505.00769},
year = {2025}
}