Statistical Characterization of Transmon Qubit Energy Relaxation Time*

Temporal fluctuations of superconducting qubit energy relaxation time, T1, bring up additional challenges in building a fault tolerant quantum computer, and larger fluctuations have been observed in those qubits with longer T1. It is believed that the fluctuation is attributed to time varying coupling of qubits to the two-level system (TLS) defects residing in the materials, but details keep unclear. In this work we analyze the transmon qubit T1 fluctuation as a function of the temperature. By carefully modeling the interactions between qubit, TLS, and quasiparticle (QP), we disentangle the contributions of the thermally excited QP and TLS on the T1 fluctuation. We also discuss different roles of the equilibrium and non-equilibrium QPs on the qubit relaxation process.