  Recently [Phys. Rev. B 91, 125433 (2015)] we derived a general formula for
the time-dependent quantum electron current through a molecular junction
subject to an arbitrary time-dependent bias within the Wide Band Limit
Approximation (WBLA) and assuming a single particle Hamiltonian. Here we
present an efficient numerical scheme for calculating the current and particle
number. Using the Pad\'e expansion of the Fermi function, it is shown that all
frequency integrals occurring in the general formula for the current can be
removed analytically. Furthermore, when the bias in the reservoirs is assumed
to be sinusoidal it is possible to manipulate the general formula into a form
containing only summations over special functions. To illustrate the method, we
consider electron transport through a one-dimensional molecular wire coupled to
two leads subject to out-of-phase biases. We also investigate finite size
effects in the current response and particle number that results from the
switch-on of such a bias.
