title: Dephasing of solid-state qubits at optimal points.
abstract: Motivated by recent experiments with Josephson-junction circuits, we analyze the influence of various noise sources on the dynamics of two-level systems at optimal operation points where the linear coupling to low-frequency fluctuations is suppressed. We study the decoherence due to nonlinear (quadratic) coupling, focusing on the experimentally relevant 1/f and Ohmic noise power spectra. For 1/f noise strong higher-order effects influence the evolution.
authors.affiliation: Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe, Germany.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Makhlin
authors.forename: Alexander
authors.initials: A
authors.lastname: Shnirman