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Nonequilibrium dynamics of two-level systems directly after cryogenic alternating bias

Iaia, Vito [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0009000429428411)·Joseph, Emily S. [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0000000181044723)·Im, Soohyun [Univ. of Wisconsin, Madison, WI (United States); State Univ. of New York (SUNY), Buffalo, NY (United States)] (ORCID:0000000196986713)·Hagopian, Nick [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0009000095353279)·O’Kelley, Sean [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)]·Kim, C. E. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)]·Materise, Nicholas [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); QuantWare BV (Netherlands)] (ORCID:0000000273534770)·Patra, Sayan [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000229231561)·Lordi, Vincenzo [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000324154656)·Eriksson, Mark A. [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0000000231309735)·Voyles, Paul M. [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0000000194384284)·Ray, Keith G. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000262417472)·Rosen, Y. J. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000346712305)
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Abstract

Two-level systems (TLSs) are a dominant decoherence mechanism in superconducting qubits, microwave kinetic inductance detectors, and quantum dots. TLSs are tunneling states commonly found in amorphous materials and interfaces, which interact electromechanically, leading to energy loss. Fluctuations in the frequency of the TLSs are a significant problem for qubit operation and force recalibration every few hours. In this study, we probe the effect of alternating bias at cryogenic temperatures on TLSs in a purpose-built LC oscillator. When an in situ alternating bias is applied, the steady-state spectra of the TLSs disappear. Spectroscopy reveals transient behavior, in which the TLS frequency fluctuates on the order of minutes. Thermal cycling above 10 K reverses these effects, restoring the TLS spectrum to its original state. Importantly, the intrinsic loss tangent of the LC oscillator remains unchanged before and after the application of the alternating bias. We propose that the disappearance of the steady-state spectrum is caused by nonequilibrium energy buildup from strain in the oxide film introduced by the pulsed voltage-bias sequence. Understanding this nonequilibrium energy could shed light on TLS fluctuations and reduce the calibration requirements for qubits.

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general physics71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITYPhysics - Classical and quantum mechanicsPhysics - Condensed matter physicsmicrowave techniquesnonequilibrium systemsopen quantum systems & decoherencequantum fluctuations & noisesuperconducting qubits

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Iaia, Vito [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0009000429428411), Joseph, Emily S. [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0000000181044723), Im, Soohyun [Univ. of Wisconsin, Madison, WI (United States); State Univ. of New York (SUNY), Buffalo, NY (United States)] (ORCID:0000000196986713), Hagopian, Nick [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0009000095353279), O’Kelley, Sean [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)], Kim, C. E. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)], Materise, Nicholas [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); QuantWare BV (Netherlands)] (ORCID:0000000273534770), Patra, Sayan [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000229231561), Lordi, Vincenzo [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000324154656), Eriksson, Mark A. [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0000000231309735), Voyles, Paul M. [Univ. of Wisconsin, Madison, WI (United States)] (ORCID:0000000194384284), Ray, Keith G. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000262417472), Rosen, Y. J. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000346712305). 2026-06-05. Nonequilibrium dynamics of two-level systems directly after cryogenic alternating bias. https://doi.org/10.1103/zjg3-rdjh

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71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS subject75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY subjectPhysics - Condensed matter physics subjectopen quantum systems & decoherence subject

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