Coherent resonant transport through a mesoscopic system with quantum ac microwave field

The time-dependent transport through an ultrasmall quantum dot coupling to two electron reservoirs is investigated. The quantum dot is perturbed by a quantum microwave field (QMF) through gate. The tunneling current formulae are obtained by taking expectation values over coherent state (CS), and SU( 1,1) CS. We derive the transport formulae at low temperature by employing t he nonequilibrium Green function technique. The currents exhibit coherent b ehaviors which are strongly associated with the applied QMF. The time-depen dent currents appear compound effects of resonant tunneling and time-oscill ating evolution. The time-averaged current and differential conductance are calculated, which manifest photon-assisted behaviors. Numerical calculatio ns reveal the similar properties as those in classical microwave field (CMF ) perturbed system for the situations concerning CS and squeezed vacuum SU( 1,1) CS. But for other squeezed SU(1,1) CS, the tunneling behavior is quite different from the system perturbed by a single CMF through gate. Due to t he quantum signal perturbation, the measurable quantities fluctuate fiercel y.