  The description of a measuring process, such as that which occurs when a
quantum point contact (QPC) detector is influenced by a nearby external
electron which can take up two possible positions, provides a interesting
application of the method of quantum damping. We find a number of new effects,
due to the complete treatment of phases afforded by the formalism, although our
results are generally similiar to those of other treatments, particularly to
those of Buks et al.
  These are effects depending on the phase shift in the detector, effects which
depend on the direction of the measuring current, and in addition to damping or
dissipative effects, an energy shift of the measured system. In particular, the
phase shift effect leads to the conclusion that there can be effects of
"observation" even when the two barriers in question pass the same current.
  The nature of the current through the barriers and its statistics is
discussed, giving a description of correlations in the current due to
"measurement" and of the origin of "telegraphic" signals.
