Transport properties of a periodically driven superconducting single-electron transistor

We discuss coherent transport of Cooper pairs through a Cooper pair shuttle. We analyze both the dc and ac Josephson effects in the two limiting cases where the charging energy E-C is either much larger or much smaller than the Josephson coupling E-J. In the limit E-J < E-C we present the detailed behavior of the critical current as a function of the damping rates and the dynamical phases. The ac effect in this regime is very sensitive to all dynamical scales present in the problem. The effect of fluctuations of the external periodic driving is discussed as well. In the opposite regime the system can be mapped onto the quantum kicked rotator, a classically chaotic system. We investigate the transport properties also in this regime, showing that the underlying classical chaotic dynamics emerges as an incoherent transfer of Cooper pairs through the shuttle. For an appropriate choice of the parameters the Cooper pair shuttle can exhibit the phenomenon of dynamical localization. We discuss in detail the properties of the localized regime as a function of the phase difference between the superconducting electrodes and the decoherence due to gate voltage fluctuations. Finally we point out how dynamical localization is reflected in the noise properties of the shuttle.