Resonant effects in the strongly driven phase-biased Cooper-pair box

The time-averaged upper level occupation probability in a strongly driven two-level system is investigated, particularly its dependence on the driving amplitude x(0) and frequency omega and the energy level separation Delta E. In contrast to the case of weak driving (x(0) << Delta E), when the positions of the resonances are almost independent of x0, in the case of the strong driving (x(0) similar to Delta E) their positions are strongly amplitude dependent. These resonances are studied in a concrete system-the strongly driven phase-biased Cooper-pair box, which is considered to be weakly coupled to the tank circuit. (c) 2006 American Institute of Physics.