  The quantum world is fascinating. It presents a description of nature that
defies our most rooted concepts about what reality is. For example, quantum
objects possess \lq\lq spooky\rq\rq\ properties that allow them to be in
multiple places at the same time, to move in different directions
simultaneously, or to exist and not to exist. In other words, to live several
parallel stories. Making use of these parallel stories to compute is the realm
of quantum computation, a world in which information is processed using the
laws of quantum physics. Nowadays, quantum computers are an object of an
extensive experimental and theoretical research, since it is known that, on
paper, these can solve many of the current computational challenges. These are
the problems that even the most sophisticated supercomputers of today, or
tomorrow, will not be able to solve.
