  The control of the quantum transport is an issue of current interest for the
construction of new devices. In this work, we investigate this possibility in
the realm of quantum graphs. The study allows the identification of two
distinct periodic quantum effects which are related to quantum complexity, one
being the identification of transport inefficiency, and the other the presence
of peaks of full transmission inside regions of suppression of transport in
some elementary arrangements of graphs. Motivated by the power of quantum
graphs, we elaborate on the construction of simple devices, based on microwave
and optical fibers networks, and also on quantum dots, nanowires and nanorings.
The elementary devices can be used to construct composed structures with
important quantum properties, which may be used to manipulate the quantum
transport.
