  We analyse the zero temperature Full Counting Statistics (FCS) for the charge
transfer across a biased tunnel junction. We find the FCS from the eigenvalues
of the density matrix of outgoing states of one lead. In the general case of a
general time-dependent bias and time-dependent transparency we solve for these
eigenvalues numerically. We report the FCS for the case of a step pulse applied
between the leads and a constant barrier transparency (this case is equivalent
to Fermi edge singularity problem). We have also studied combinations of a
time-dependent barrier transparency and biases between the leads. In particular
we look at protocols which excite the minimal number of excitations for a given
charge transfer (low noise electron source) and protocols which maximise
entanglement of charge states.
