Energy decay and frequency shift of a superconducting qubit from non-equilibrium quasiparticles

Abstract

Quasiparticles are an important decoherence mechanism in superconducting qubits, and can be described with a complex admittance that is a generalization of the Mattis-Bardeen theory. By injecting non-equilibrium quasiparticles with a tunnel junction, we verify qualitatively the expected change of the decay rate and frequency in a phase qubit. With their relative change in agreement to within 4% of prediction, the theory can be reliably used to infer quasiparticle density. We describe how settling of the decay rate may allow determination of whether qubit energy relaxation is limited by non-equilibrium quasiparticles.

Main paper: 4 pages, 3 figures, 1 table. Supplementary material: 8 pages, 3 figures

References in corpus (8)

• Observation of quantum jumps in a superconducting artificial atom
• Experimental evidence for a surface distribution of two-level systems in superconducting lithographed microwave resonators
• Microwave Dielectric Loss at Single Photon Energies and milliKelvin Temperatures
• Deterministic entanglement of photons in two superconducting microwave resonators
• Quasiparticle relaxation of superconducting qubits in the presence of flux
• Photon shell game in three-resonator circuit quantum electrodynamics
• Superconducting Qubits and the Physics of Josephson Junctions
• Effect of Quasiparticles Injection on the AC Response of a Superconductor