  The theory of time-dependent quantum transport addresses the question: How do
electrons flow through a junction under the influence of an external
perturbation as time goes by? In this paper, we invert this question and search
for a time-dependent bias such that the system behaves in a desired way. This
can, for example, be an observable that is forced to follow a certain pattern
or the minimization of an objective function which depends on the observables.
Our system of choice consists of quantum dots coupled to normal or
superconducting leads. We present results for junctions with normal leads where
the current, the density or a molecular vibration is optimized to follow a
given target pattern. For junctions with two superconducting leads, where the
Josephson effect triggers the current to oscillate, we show how to suppress the
Josephson oscillations by suitably tailoring the bias. In a second example
involving superconductivity, we consider a Y shaped junction with two quantum
dots coupled to one superconducting and two normal leads. This device is used
as a Cooper pair splitter to create entangled electrons on the two quantum
dots. We maximize the splitting efficiency with the help of an optimized bias.
