Silent phase qubit based on d-wave Josephson junctions -: art. no. 064516

A flux qubit is designed and fabricated that capitalizes on intrinsic properties of submicron YBCO (yttrium-barium-copper oxide high-T-c superconductor) grain boundary junctions. The operating point is protected from the fluctuations of the external fields, already on the classical level. The effects of external perturbations only appear in the third or fourth order, depending on the character of the coupling. The estimates of the decoherence due to fluctuations of the external flux show that an experimental observation of coherent quantum tunneling and Rabi oscillations in the system is feasible.