  The Braess paradox, known for traffic and other classical networks, lies in
the fact that adding a new route to a congested network in an attempt to
relieve congestion can counter-intuitively degrade the overall network
performance. Recently, we have extended the concept of Braess paradox to
semiconductor mesoscopic networks, whose transport properties are governed by
quantum physics. In this paper, we demonstrate theoretically that, alike in
classical systems, congestion plays a key role in the occurrence of a Braess
paradox in mesoscopic networks.
