  Most functionalities of modern electronic circuits rely on the possibility to
modify the path fol- lowed by the electrons using, e.g. field effect
transistors. Here we discuss the interplay between the modification of this
path and the quantum dynamics of the electronic flow. Specifically, we study
the propagation of charge pulses through the edge states of a two-dimensional
electron gas in the quantum Hall regime. By sending radio-frequency (RF)
excitations on a top gate capacitively coupled to the electron gas, we
manipulate these edge state dynamically. We find that a fast RF change of the
gate voltage can stop the propagation of the charge pulse inside the sample.
This effect is intimately linked to the vanishing velocity of bulk states in
the quantum Hall regime and the peculiar connection between momentum and
transverse confinement of Landau levels. Our findings suggest new possibilities
for stopping, releasing and switching the trajectory of charge pulses in
quantum Hall systems.
