Characterization of Radiation-Induced Errors in Superconducting Qubits Protected with Various Gap-Engineering Strategies

Quantum Physics [Submitted on 13 Mar 2026] Characterization of Radiation-Induced Errors in Superconducting Qubits Protected with Various Gap-Engineering Strategies H. Douglas Pinckney, Thomas McJunkin, Alan W. Hunt, Patrick M. Harrington, Hannah P. Binney, Max Hays, Yenuel Jones-Alberty, Kate Azar, Felipe Contipelli, Renée DePencier Piñero, Jeffrey M. Gertler, Michael Gingras, Aranya Goswami, Cyrus F. Hirjibehedin, Mingyu Li, Mathis Moes, Bethany M. Niedzielski, Mallika T. Randeria, Ryan Sitler, Matthew K. Spear, Hannah Stickler, Jiatong Yang, Wouter Van De Pontseele, Mollie E. Schwartz, Jeffrey A. Grover, Kevin Schultz, Kyle Serniak, Joseph A. Formaggio, William D. Oliver Impacts from high-energy particles cause correlated errors in superconducting qubits by increasing the quasiparticle density in the vicinity of the Josephson junctions (JJs). Such errors are particularly harmful as they cannot be easily remedied via conventional error correcting codes. Recent experiments reduced correlated errors by making the difference in superconducting gap energy across the JJ larger than the qubit energy. In this work, we assess gap engineering near the JJ (\delta\Delta_{\mathrm{JJ}}) and the capacitor/ground-plane (\delta\Delta_{\mathrm{M1}}) by exposing arrays of transmon qubits to two sources of radiation. For \alpha-particles from an ^{241}Am source, we observe T_1 errors correlated in space and time, supporting a hypothesis that hadronic cosmic rays are a major contributor to the 10^{-10} error floor observed in Ref. 1. For electrons from a pulsed linear accelerator, we observe temporally correlated T_1 and T_2 errors, this measurement is insensitive to spatial correlations. We observe that the severity of correlated T_1 errors is reduced for qubit arrays with a greater degree of gap engineering at the JJ. For both T_1 and T_2 errors, the recovery time is hastened by an increased \delta\Delta_{\mathrm{M1}}, which we attribute to the trapping of quasiparticles into the capacitor/ground-plane. We construct a model of quasiparticle dynamics that qualitatively agrees with our observations. This work reinforces the multifaceted influence of radiation on superconducting qubits and provides strategies for improving radiation resilience. Comments: 30 pages, 18 figures Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Instrumentation and Detectors (physics.ins-det) Cite as: arXiv:2603.13460 [quant-ph]   (or arXiv:2603.13460v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.13460 Focus to learn more Submission history From: H Douglas Pinckney [view email] [v1] Fri, 13 Mar 2026 17:05:51 UTC (1,433 KB) Access Paper: HTML (experimental) view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 Change to browse by: cond-mat cond-mat.mes-hall physics physics.ins-det References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)