TLS Dynamics in a Superconducting Qubit Due to Background Ionizing Radiation

• Main Authors: Thorbeck, Ted, Eddins, Andrew, Lauer, Isaac, McClure, Douglas T, Carroll, Malcolm
• Format: Journal Article
• Language: English
• Published: 10-10-2022
• Subjects: Physics - Mesoscale and Nanoscale Physics; Physics - Quantum Physics
• DOI: 10.48550/arxiv.2210.04780

PRX Quantum 4, 020356, 2023 Superconducting qubit lifetimes must be both long and stable to provide an
adequate foundation for quantum computing. This stability is imperiled by
two-level systems (TLSs), currently a dominant loss mechanism, which exhibit
slow spectral dynamics that destabilize qubit lifetimes on hour timescales.
Stability is also threatened at millisecond timescales, where ionizing
radiation has recently been found to cause bursts of correlated multi-qubit
decays, complicating quantum error correction. Here we study both ionizing
radiation and TLS dynamics on a 27-qubit processor, repurposing the standard
transmon qubits as sensors of both radiation impacts and TLS dynamics. Unlike
prior literature, we observe resilience of the qubit lifetimes to the transient
quasiparticles generated by the impact of radiation. However, we also observe a
new interaction between these two processes, "TLS scrambling," in which a
radiation impact causes multiple TLSs to jump in frequency, which we suggest is
due to the same charge rearrangement sensed by qubits near a radiation impact.
As TLS scrambling brings TLSs out of or in to resonance with the qubit, the
lifetime of the qubit increases or decreases. Our findings thus identify
radiation as a new contribution to fluctuations in qubit lifetimes, with
implications for efforts to characterize and improve device stability