Readout-induced degradation of transmon lifetimes: interplay of TLSs and qubit spectral reshaping

Quantum Physics [Submitted on 14 Mar 2026] Readout-induced degradation of transmon lifetimes: interplay of TLSs and qubit spectral reshaping Ziwen Huang, Jimmy Shih-Chun Hung, Mouktik Raha, Ming-Han Chou, Harry Levine, Alex Retzker, Connor T. Hann, David Hover, Fernando G.S.L. Brandão, Aashish A. Clerk, Arbel Haim, Oskar Painter Measurement backaction degrades dispersive readout of superconducting qubits even at modest drive strengths, often via the reduction of qubit lifetimes during readout. In this work, we theoretically and experimentally study this degradation and show how it can result from the interplay between detuned two-level systems (TLSs) and a drive-renormalized qubit spectrum. For modest to strong readout, the qubit emission spectrum becomes non-Lorentzian and depends sensitively on the readout drive frequency (even when measurement rate is fixed). We combine the readout-modified qubit emission spectrum with time-dependent perturbation theory to predict qubit lifetimes in the presence of a TLS bath. Master equation simulations and experimental measurements on a frequency-tunable transmon confirm these predictions quantitatively. In particular, we find that driving at the resonator frequency associated with the qubit ground state yields the narrowest qubit emission spectrum and the least lifetime degradation for a fixed measurement rate, providing a practical guideline for optimizing readout protocols in future quantum processors. Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.13857 [quant-ph]   (or arXiv:2603.13857v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.13857 Focus to learn more Submission history From: Ziwen Huang [view email] [v1] Sat, 14 Mar 2026 09:35:25 UTC (3,171 KB) Access Paper: view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 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?)