Dissipation in a superconducting artificial atom due to a single non-equilibrium quasiparticle

TL;DR

This paper investigates how a single non-equilibrium quasiparticle causes dissipation in a superconducting artificial atom, revealing that increased drive power can enhance the resonance quality factor due to quasiparticle energy dependence.

Contribution

It provides a detailed analysis of quasiparticle-induced dissipation in superconducting artificial atoms, including the effects of quasiparticle heating and the energy-dependent density of states.

Findings

Resonance quality factor increases with drive power in nearly harmonic spectra.

Quasiparticle heating affects dissipation and resonance behavior.

Energy dependence of quasiparticle density of states explains counterintuitive results.

Abstract

We study a superconducting artificial atom which is represented by a single Josephson junction or a Josephson junction chain, capacitively coupled to a coherently driven transmission line, and which contains exactly one residual quasiparticle (or up to one quasiparticle per island in a chain). We study the dissipation in the atom induced by the quasiparticle tunneling, taking into account the quasiparticle heating by the drive. We calculate the transmission coefficient in the transmission line for drive frequencies near resonance and show that, when the artificial atom spectrum is nearly harmonic, the intrinsic quality factor of the resonance increases with the drive power. This counterintuitive behavior is due to the energy dependence of the quasiparticle density of states.