1207.6825 (K. Inomata et al.)

Large Dispersive Shift of Cavity Resonance Induced by a Superconducting
Flux Qubit in the Straddling Regime    [PDF]

K. Inomata, T. Yamamoto, B. -M. Billangeon, Y. Nakamura, J. S. Tsai

We demonstrate enhancement of the dispersive frequency shift in a coplanar waveguide resonator induced by a capacitively-coupled superconducting flux qubit in the straddling regime. The magnitude of the observed shift, 80 MHz for the qubit-resonator detuning of 5 GHz, is quantitatively explained by the generalized Jaynes-Cummings model which takes into account the contribution of the qubit higher energy levels. By applying the enhanced dispersive shift to the qubit readout, we achieved 90% contrast of the Rabi oscillations which is mainly limited by the energy relaxation of the qubit.

View original: http://arxiv.org/abs/1207.6825