  We study the electron transport through a quantum wire under the influence of
external time-dependent gate voltages. The wire is modelled by a tight-binding
Hamiltonian for which we obtain the current from the corresponding
transmission. The numerical evaluation of the dc current reveals that for
bichromatic driving, the conductance depends sensitively on the
commensurability of the driving frequencies. The current even possesses a
discontinuous frequency dependence. Moreover, we find that the conductance as a
function of the wire length oscillates with a period that depends on the ratio
between the driving frequencies.
