Qubit dephasing due to quasiparticle tunneling
Sebastian Zanker, Michael Marthaler
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 dephasing $\ensuremath{\sim}exp[\ensuremath{-}x(t)]$ where $x(t)\ensuremath{\propto}{t}^{3/2}$ for short-time scales and $x(t)\ensuremath{\propto}t\phantom{\rule{0.16em}{0ex}}ln(t)$ for long-time scales.
arXiv:1410.8715•Physical Review B•May 7, 2015•12 citations