Qubit dephasing due to Quasiparticle Tunneling

Abstract

We study dephasing of a superconducting qubit due to quasiparticle tunneling through a Josephson junction. While qubit decay due to tunneling processes is well understood within a golden rule approximation, pure dephasing due to BCS quasiparticles gives rise to a divergent golden rule rate. We calculate qubit dephasing due to quasiparticle tunneling beyond lowest order approximation in coupling between qubit and quasiparticles. Summing up a certain class of diagrams we show that qubit dephasing due to purely longitudinal coupling to quasiparticles leads to a dephasing $\sim \exp (-x(t))$ where $x(t)$ is not linear in time on short time scales while it tends towards a selfconsistent calculated dephasing rate for longer times.

10 pages, 2 figures

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• Dephasing due to quasiparticle tunneling in fluxonium qubits: a phenomenological approach
• Shortcuts to adiabaticity in superconducting circuits for fast multi-partite state generation
• Theory of quasiparticle-induced errors in driven-dissipative Schrödinger cat qubits
• Distortion of a reduced equilibrium density matrix: influence on quantum emulation