Superconducting circuits host two-level systems with lifetimes exceeding one second
Abstract
Understanding the microscopic environment of superconducting qubits is a central challenge for quantum technologies. Parasitic two-level systems (TLSs) of various microscopic origins are ubiquitous and limit qubit performance through decoherence, frequency drifts, and leakage. Recently, long-lived TLSs with lifetimes exceeding those of state-of-the-art qubits have been shown to induce correlated qubit dynamics, with direct implications for quantum error correction. Here, we perform wide-band quantum-jump correlation spectroscopy on flux-tunable transmon qubits and identify microscopic degrees of freedom that outlive the qubit by orders of magnitude. Pump-probe measurements at varying detunings from these objects reveal intrinsic lifetimes exceeding one second. Their weak coupling to the qubit, in the kilohertz range, is consistent with positional defects described by the standard tunneling model, without excluding other microscopic origins such as magnetic spin impurities or trapped quasiparticles. More broadly, these results establish superconducting qubits as a sensitive probe of exceptionally long-lived microscopic degrees of freedom and open a route toward their controlled access and functionalization.
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BibTeX
@misc{fechant2026superconducting,
title = {{Superconducting circuits host two-level systems with lifetimes exceeding one second}},
author = {Mathieu Féchant and Phillip Lenhard and Nicolas Gosling and Ritika Dhundhwal and Denis Bénâtre and Wolfgang Wernsdorfer and Thomas Reisinger and Ioan M. Pop},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21853},
eprint = {2610.21853},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21853},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Superconducting circuits host two-level systems with lifetimes exceeding one second
AU - Mathieu Féchant
AU - Phillip Lenhard
AU - Nicolas Gosling
AU - Ritika Dhundhwal
AU - Denis Bénâtre
AU - Wolfgang Wernsdorfer
AU - Thomas Reisinger
AU - Ioan M. Pop
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.21853
UR - https://arxiv.org/abs/2610.21853
AB - Understanding the microscopic environment of superconducting qubits is a central challenge for quantum technologies. Parasitic two-level systems (TLSs) of various microscopic origins are ubiquitous and limit qubit performance through decoherence, frequency drifts, and leakage. Recently, long-lived TLSs with lifetimes exceeding those of state-of-the-art qubits have been shown to induce correlated qubit dynamics, with direct implications for quantum error correction. Here, we perform wide-band quantum-jump correlation spectroscopy on flux-tunable transmon qubits and identify microscopic degrees of freedom that outlive the qubit by orders of magnitude. Pump-probe measurements at varying detunings from these objects reveal intrinsic lifetimes exceeding one second. Their weak coupling to the qubit, in the kilohertz range, is consistent with positional defects described by the standard tunneling model, without excluding other microscopic origins such as magnetic spin impurities or trapped quasiparticles. More broadly, these results establish superconducting qubits as a sensitive probe of exceptionally long-lived microscopic degrees of freedom and open a route toward their controlled access and functionalization.
ER -