  Practical mesoscopic devices based on quantum point contacts (QPCs) must
function at operating point involving large internal driving fields.
Experimental evidence has accumulated to display anomalous nonlinear features
of QPC response beyond the capacities of accepted tunnelling-based models of
nonlinear quantum transport. Here we recall the physical setting of three
anomalous QPC experiments and review how, for two of them, a microscopically
based nonequilibrium quantum kinetic description (the correct physical boundary
conditions being crucial) has already overcome the predictive limitations of
standard nonequilibrium mesoscopic models. The third experiment remains a
significant challenge to all theorists.
