Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

FP5

SQUBIT-2 Sintesi della relazione

Project ID: IST-2001-39083
Finanziato nell'ambito di: FP5-IST
Paese: Germany

Dephasing of solid-state Qubits at optimal point

Several breakthrough experiments with Josephson-junction circuits performed by, e.g., SQUBIT-2 partners from Saclay, Delft, and Chalmers showed that decoherence can be dramatically suppressed at optimal operation points where the linear coupling to low-frequency fluctuations vanishes. We analysed the influence of various noise sources on the dynamics of two-level systems at optimal operation points due to non-linear (quadratic) coupling. We focused on the experimentally relevant 1/f and Ohmic noise power spectra. For 1/f noise strong higher-order effects influence the evolution.

As a result the amplitude of coherent oscillations decays according to a power law rather than exponentially. This prediction has been verified experimentally. Characterization of decoherence at optimal points is very important for understanding the fundamental limitation on operation of Josephson circuits as qubits.

Reported by

UNIVERSITY OF KARLSRUHE
INSTITUT FUR THEORETISCHE FESTKORPERPHYSIK
76128 KARLSRUHE
Germany