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  • Open Access

Readout-Induced Degradation of Transmon Lifetimes: Interplay of TLSs and Qubit Spectral Reshaping

Ziwen Huang1,*, Jimmy Shih-Chun Hung1,*, Mouktik Raha1, Ming-Han Chou1, Harry Levine1,2, Alex Retzker1,3, Connor T. Hann1, David Hover1, Fernando G. S. L. Brandão1,4 et al.

Aashish A. Clerk1,5, Arbel Haim1, and Oskar Painter1,4,6

  • *These authors contributed equally to this work.
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PRX Quantum 7, 033059 – Published 17 September, 2026

DOI: https://doi.org/10.1103/y5ty-bd4y

Abstract

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 the 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.

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Popular Summary

Quantum computing holds enormous potential to transform how we solve some of the hardest problems in science and engineering. But fully realizing that potential demands that we read out quantum information not only accurately but also quickly and with minimal disruption to the fragile quantum state being measured. Superconducting circuits are one of the most promising platforms for building quantum computers, in part because their readout scheme is naturally convenient and, in principle, nondestructive. In practice, however, faster readout means driving the system harder, which can cause the qubit to interact more strongly with tiny material imperfections in its environment. The result is that quantum information decays faster during the stronger measurement. Overcoming this trade-off is a key challenge on the path to large-scale quantum processors. In this work, we not only clearly explain this detrimental effect quantitatively but also identify a practical strategy to significantly mitigate it. Through a combination of analytical theory, numerical simulations, and experiments, which are in excellent quantitative agreement, we show that the frequency used to perform the readout plays a critical role in how much damage the measurement inflicts. By choosing this frequency carefully, we can substantially reduce the loss of quantum information without sacrificing measurement speed. This insight provides an immediately actionable guideline for improving readout in future large-scale quantum processors.

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References (41)

  1. A. Blais, R.-S. Huang, A. Wallraff, S. M. Girvin, and R. J. Schoelkopf, Cavity quantum electrodynamics for superconducting electrical circuits: An architecture for quantum computation, Phys. Rev. A 69, 062320 (2004).
  2. A. Wallraff, D. I. Schuster, A. Blais, L. Frunzio, R.-S. Huang, J. Majer, S. Kumar, S. M. Girvin, and R. J. Schoelkopf, Strong coupling of a single photon to a superconducting qubit using circuit quantum electrodynamics, Nature (London) 431, 162 (2004).
  3. A. Blais, A. L. Grimsmo, S. M. Girvin, and A. Wallraff, Circuit quantum electrodynamics, Rev. Mod. Phys. 93, 025005 (2021).
  4. P. Krantz, M. Kjaergaard, F. Yan, T. P. Orlando, S. Gustavsson, and W. D. Oliver, A quantum engineer’s guide to superconducting qubits, Appl. Phys. Rev. 6, 021318 (2019).
  5. E. Jeffrey, D. Sank, J. Y. Mutus, T. C. White, J. Kelly, R. Barends, Y. Chen, Z. Chen, B. Chiaro, A. Dunsworth, A. Megrant, P. J. J. O’Malley, C. Neill, P. Roushan, A. Vainsencher, J. Wenner, A. N. Cleland, and J. M. Martinis, Fast accurate state measurement with superconducting qubits, Phys. Rev. Lett. 112, 190504 (2014).
  6. T. Walter, P. Kurpiers, S. Gasparinetti, P. Magnard, A. Potočnik, Y. Salathé, M. Pechal, M. Mondal, M. Oppliger, C. Eichler, and A. Wallraff, Rapid high-fidelity single-shot dispersive readout of superconducting qubits, Phys. Rev. Appl. 7, 054020 (2017).
  7. J. Heinsoo, C. K. Andersen, A. Remm, S. Krinner, T. Walter, Y. Salathé, S. Gasparinetti, J.-C. Besse, A. Potočnik, A. Wallraff, and C. Eichler, Rapid high-fidelity multiplexed readout of superconducting qubits, Phys. Rev. Appl. 10, 034040 (2018).
  8. Google Quantum AI and Collaborators, Quantum error correction below the surface code threshold, Nature (London) 638, 920 (2025).
  9. Y. Kim, A. Eddins, S. Anand, K. X. Wei, E. van den Berg, S. Rosenblatt, H. Nayfeh, Y. Wu, M. Zaletel, K. Temme, and A. Kandala, Evidence for the utility of quantum computing before fault tolerance, Nature (London) 618, 500 (2023).
  10. A. Bengtsson, A. Opremcak, M. Khezri, D. Sank, A. Bourassa, K. J. Satzinger, S. Hong, C. Erickson, B. J. Lester, K. C. Miao, A. N. Korotkov, J. Kelly, Z. Chen, and P. V. Klimov, Model-based optimization of superconducting qubit readout, Phys. Rev. Lett. 132, 100603 (2024).
  11. A. G. Fowler, M. Mariantoni, J. M. Martinis, and A. N. Cleland, Surface codes: Towards practical large-scale quantum computation, Phys. Rev. A 86, 032324 (2012).
  12. S. Bravyi, A. W. Cross, J. M. Gambetta, D. Maslov, P. Rall, and T. J. Yoder, High-threshold and low-overhead fault-tolerant quantum memory, Nature (London) 627, 778 (2024).
  13. D. Sank et al., Measurement-induced state transitions in a superconducting qubit: Beyond the rotating wave approximation, Phys. Rev. Lett. 117, 190503 (2016).
  14. M. Khezri, A. Opremcak, Z. Chen, K. C. Miao, M. McEwen, A. Bengtsson, T. White, O. Naaman, D. Sank, A. N. Korotkov, Y. Chen, and V. Smelyanskiy, Measurement-induced state transitions in a superconducting qubit: Within the rotating-wave approximation, Phys. Rev. Appl. 20, 054008 (2023).
  15. M. F. Dumas, B. Groleau-Paré, A. McDonald, M. H. Muñoz Arias, C. Lledó, B. D’Anjou, and A. Blais, Measurement-induced transmon ionization, Phys. Rev. X 14, 041023 (2024).
  16. W. Dai, S. Hazra, D. K. Weiss, P. D. Kurilovich, T. Connolly, H. K. Babla, S. Singh, V. R. Joshi, A. Z. Ding, P. D. Parakh, J. Venkatraman, X. Xiao, L. Frunzio, and M. H. Devoret, Characterization of drive-induced unwanted state transitions in superconducting circuits, Phys. Rev. X 16, 011011 (2026).
  17. S. Hazra, W. Dai, T. Connolly, P. D. Kurilovich, Z. Wang, L. Frunzio, and M. H. Devoret, Benchmarking the readout of a superconducting qubit for repeated measurements, Phys. Rev. Lett. 134, 100601 (2025).
  18. T. Thorbeck, Z. Xiao, A. Kamal, and L. C. G. Govia, Readout-induced suppression and enhancement of superconducting qubit lifetimes, Phys. Rev. Lett. 132, 090602 (2024).
  19. P. M. Harrington, J. T. Monroe, and K. W. Murch, Quantum zeno effects from measurement controlled qubit-bath interactions, Phys. Rev. Lett. 118, 240401 (2017).
  20. A. Bista, M. Thibodeau, K. Nie, K. Chow, B. K. Clark, and A. Kou, Readout-induced leakage of the fluxonium qubit, Phys. Rev. Appl. 25, 034058 (2026).
  21. H. Levine et al., Demonstrating a long-coherence dual-rail erasure qubit using tunable transmons, Phys. Rev. X 14, 011051 (2024).
  22. A. Kubica, A. Haim, Y. Vaknin, H. Levine, F. Brandão, and A. Retzker, Erasure qubits: Overcoming the T1 limit in superconducting circuits, Phys. Rev. X 13, 041022 (2023).
  23. D. Sank, A. Opremcak, A. Bengtsson, M. Khezri, J. Chen, O. Naaman, and A. Korotkov, System characterization of dispersive readout in superconducting qubits, Phys. Rev. Appl. 23, 024055 (2025).
  24. J. Gambetta, A. Blais, D. I. Schuster, A. Wallraff, L. Frunzio, J. Majer, M. H. Devoret, S. M. Girvin, and R. J. Schoelkopf, Qubit-photon interactions in a cavity: Measurement-induced dephasing and number splitting, Phys. Rev. A 74, 042318 (2006).
  25. A. A. Clerk and D. W. Utami, Using a qubit to measure photon-number statistics of a driven thermal oscillator, Phys. Rev. A 75, 042302 (2007).
  26. J. Koch, T. M. Yu, J. Gambetta, A. A. Houck, D. I. Schuster, J. Majer, A. Blais, M. H. Devoret, S. M. Girvin, and R. J. Schoelkopf, Charge-insensitive qubit design derived from the cooper pair box, Phys. Rev. A 76, 042319 (2007).
  27. E. A. Sete, J. M. Martinis, and A. N. Korotkov, Quantum theory of a bandpass purcell filter for qubit readout, Phys. Rev. A 92, 012325 (2015).
  28. F. Swiadek, R. Shillito, P. Magnard, A. Remm, C. Hellings, N. Lacroix, Q. Ficheux, D. C. Zanuz, G. J. Norris, A. Blais, S. Krinner, and A. Wallraff, Enhancing dispersive readout of superconducting qubits through dynamic control of the dispersive shift: Experiment and theory, PRX Quantum 5, 040326 (2024).
  29. A. G. Kofman and G. Kurizki, Acceleration of quantum decay processes by frequent observations, Nature (London) 405, 546 (2000).
  30. J. Gambetta, A. Blais, M. Boissonneault, A. A. Houck, D. I. Schuster, and S. M. Girvin, Quantum trajectory approach to circuit QED: Quantum jumps and the Zeno effect, Phys. Rev. A 77, 012112 (2008).
  31. J. R. Johansson, P. D. Nation, and F. Nori, QuTiP: An open-source python framework for the dynamics of open quantum systems, Comput. Phys. Commun. 183, 1760 (2012).
  32. A. Shnirman, G. Schön, I. Martin, and Y. Makhlin, Low- and high-frequency noise from coherent two-level systems, Phys. Rev. Lett. 94, 127002 (2005).
  33. X. You, A. A. Clerk, and J. Koch, Positive- and negative-frequency noise from an ensemble of two-level fluctuators, Phys. Rev. Res. 3, 013045 (2021).
  34. R. Barends, J. Kelly, A. Megrant, D. Sank, E. Jeffrey, Y. Chen, Y. Yin, B. Chiaro, J. Mutus, C. Neill, P. O’Malley, P. Roushan, J. Wenner, T. C. White, A. N. Cleland, and J. M. Martinis, Coherent Josephson qubit suitable for scalable quantum integrated circuits, Phys. Rev. Lett. 111, 080502 (2013).
  35. C. Müller, A. Shnirman, and Y. Makhlin, Relaxation of Josephson qubits due to strong coupling to two-level systems, Phys. Rev. B 80, 134517 (2009).
  36. S. Vallés-Sanclemente, T. H. F. Vroomans, T. R. van Abswoude, F. Brulleman, T. Stavenga, S. L. M. van der Meer, Y. Xin, A. Lawrence, V. Singh, M. A. Rol, and L. DiCarlo, Optimizing the frequency positioning of tunable couplers in a circuit QED processor to mitigate spectator effects on quantum operations, Phys. Rev. Lett. 136, 200801 (2026).
  37. C. C. Bultink, B. Tarasinski, N. Haandbæk, S. Poletto, N. Haider, D. J. Michalak, A. Bruno, and L. DiCarlo, General method for extracting the quantum efficiency of dispersive qubit readout in circuit QED, Appl. Phys. Lett. 112, 092601 (2018).
  38. A. Y. Dmitriev, R. Shaikhaidarov, V. N. Antonov, T. Hönigl-Decrinis, and O. V. Astafiev, Quantum wave mixing and visualisation of coherent and superposed photonic states in a waveguide, Nat. Commun. 8, 1352 (2017).
  39. Y. Zhang, B. J. Lester, Y. Y. Gao, L. Jiang, R. J. Schoelkopf, and S. M. Girvin, Engineering bilinear mode coupling in circuit QED: Theory and experiment, Phys. Rev. A 99, 012314 (2019).
  40. Y. Y. Gao, B. J. Lester, Y. Zhang, C. Wang, S. Rosenblum, L. Frunzio, L. Jiang, S. M. Girvin, and R. J. Schoelkopf, Programmable interference between two microwave quantum memories, Phys. Rev. X 8, 021073 (2018).
  41. N. E. Frattini, U. Vool, S. Shankar, A. Narla, K. M. Sliwa, and M. H. Devoret, 3-wave mixing josephson dipole element, Appl. Phys. Lett. 110, 222603 (2017).

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PRX Quantum 7, 033059– Published 17 September, 2026
  • Received 10 April 2026
  • Accepted 22 July 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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