Fractional revivals of coherence in quantum mechanical oscillators

A case study is made of the delocalisation and revival dynamics of a continuously driven quantum pendulum in integrable and near integrable regimes, utilising the Husimi phase-space distribution function, and an entropy function which measures the degree of localisation. The numerical results can be well understood in terms of a simple model description based on a quasi-energy representation. Two important time-scales of the evolution are derived, and the model description appears to remain highly accurate in the region of classical KAM-tori, even in the driven case.