  We consider coherent feedback control of quantum transport and focus on the
application of simple controllers and the effects of a finite bias voltage. We
show that simple single-parameter controllers can give rise to a range of
useful effects such as amplification of changes in plant transmission,
increased resolution of energy filtration, and the detection of differences
between otherwise indistinguishable plants. We explore how these effects are
impacted by the phase-averaging effects associated with the application of a
finite bias and identify important voltage scales for the maintenance of the
functionalities achieved through feedback control.
