Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 7: Transport: Quantum coherence and quantum information systems - Theory (TT with HL)
HL 7.5: Talk
Monday, March 16, 2015, 10:30–10:45, H 3005
Qubit dephasing due to Quasiparticle Tunneling — •Sebastian Zanker, Michael Marthaler, and Gerd Schön — Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany
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 ∼ exp(−x(t)) where x(t)∝ t3/2 for short time scales and x(t) ∝ tlog(t) for long time scales.