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

Abstract

Temporal fluctuations in the superconducting qubit lifetime, $T_1$, bring up additional challenges in building a fault-tolerant quantum computer. While the exact mechanisms remain unclear, $T_1$ fluctuations are generally attributed to the strong coupling between the qubit and a few near-resonant two-level systems (TLSs) that can exchange energy with an assemble of thermally fluctuating two-level fluctuators (TLFs) at low frequencies. Here, we report $T_1$ measurements on the qubits with different geometrical footprints and surface dielectrics as a function of the temperature. By analyzing the noise spectrum of the qubit depolarization rate, ${\Gamma }_1=1/T_1$, we can disentangle the impact of TLSs, non-equilibrium quasiparticles (QPs), and equilibrium (thermally excited) QPs on the variance in ${\Gamma }_1$. We find that ${\Gamma }_1$ variances in the qubit with a small footprint are more susceptible to the QP and TLS fluctuations than those in the large-footprint qubits. Furthermore, the QP-induced variances in all qubits are consistent with the theoretical framework of QP diffusion and fluctuation. We suggest these findings can offer valuable insights for future qubit design and engineering optimization.

arXiv comment6+5 pages, 3+4 figures

References in corpus (31)

• Supplementary information for "Quantum supremacy using a programmable superconducting processor"
• Circuit Quantum Electrodynamics
• A Quantum Engineer's Guide to Superconducting Qubits
• The Flux Qubit Revisited to Enhance Coherence and Reproducibility
• Towards understanding two-level-systems in amorphous solids -- Insights from quantum circuits
• Experimental evidence for a surface distribution of two-level systems in superconducting lithographed microwave resonators
• Surface participation and dielectric loss in superconducting qubits
• Fluctuations of Energy-Relaxation Times in Superconducting Qubits
• Decoherence benchmarking of superconducting qubits
• Hot non-equilibrium quasiparticles in transmon qubits
• Correlating decoherence in transmon qubits: Low frequency noise by single fluctuators
• Surface loss simulations of superconducting coplanar waveguide resonators
• Number fluctuations of sparse quasiparticles in a superconductor
• Three-dimensional superconducting resonators at $T<20$ mK with the photon lifetime up to $\tau =2$ seconds
• Quasiparticle relaxation of superconducting qubits in the presence of flux
• Determining interface dielectric losses in superconducting coplanar waveguide resonators
• Interacting two-level defects as sources of fluctuating high-frequency noise in superconducting circuits
• Non-Poissonian Quantum Jumps of a Fluxonium Qubit due to Quasiparticle Excitations
• Systematic Improvements in Transmon Qubit Coherence Enabled by Niobium Surface Encapsulation
• Energy decay and frequency shift of a superconducting qubit from non-equilibrium quasiparticles
• Investigating surface loss effects in superconducting transmon qubits
• Decoherence spectroscopy with individual two-level tunneling defects
• Normal-metal quasiparticle traps for superconducting qubits
• Disentangling Losses in Tantalum Superconducting Circuits
• Phonon downconversion to suppress correlated errors in superconducting qubits
• Bogoliubov Quasiparticles in Superconducting Qubits
• Resolving the positions of defects in superconducting quantum bits
• Coexistence of nonequilibrium density and equilibrium energy distribution of quasiparticles in a superconducting qubit
• Efficient quasiparticle traps with low dissipation through gap engineering
• Positive- and negative-frequency noise from an ensemble of two-level fluctuators
• Stabilizing and improving qubit coherence by engineering noise spectrum of two-level systems

Cited by in corpus (1)

• Coherence-Mediated Quantum Thermometry in a Hybrid Circuit-QED Architecture