We consider the use of a pi junction for flux qubits to realize degenerate quantum levels without external magnetic field. On the basis of the Caldeira-Leggett model, we derive an effective spin-Boson model and study decoherence of this type of qubits. We estimate the dephasing time by using parameters from recent experiments of superconductor-insulator-ferromagnet-superconductor junctions and show that high critical current and large subgap resistance are required for the pi junction to realize a long coherent time.
|Journal||Physical review B: Condensed matter and materials physics|
|Publication status||Published - 2007|