Disentangling the Impact of Quasiparticles and Two-Level Systems on the Statistics of Superconducting Qubit Lifetime

• DOI: 10.48550/arxiv.2409.09926
• Publication Date: 2024-09-15
• Authors: Shaojiang Zhu; Xinyuan You; Uğur Alyanak; Mustafa Bal; Francesco Crisa; Sabrina Garattoni; Andrei Lunin; Roman Pilipenko; Akshay A. Murthy; Alexander Romanenko; Anna Grassellino
• Keywords: Charge qubit; Flux qubit; Transmon

Temporal fluctuations in the superconducting qubit lifetime, $T_1$, bring up additional challenges building a fault-tolerant quantum computer. While exact mechanisms remain unclear, $T_1$ are generally attributed to strong coupling between and few near-resonant two-level systems (TLSs) that can exchange energy with an assemble of thermally fluctuating fluctuators (TLFs) at low frequencies. Here, we report measurements on qubits different geometrical footprints surface dielectrics as function temperature. By analyzing noise spectrum depolarization rate, $\Gamma_1 = 1/T_1$, disentangle impact TLSs, non-equilibrium quasiparticles (QPs), equilibrium (thermally excited) QPs variance $\Gamma_1$. We find $\Gamma_1$ variances small footprint more susceptible QP TLS than those large-footprint qubits. Furthermore, QP-induced all consistent theoretical framework diffusion fluctuation. suggest these findings offer valuable insights for future design engineering optimization.