  The informational approach to continuous quantum measurement is derived from
POVM formalism for a mesoscopic scattering detector measuring a charge qubit.
Quantum Bayesian equations for the qubit density matrix are derived, and cast
into the form of a stochastic conformal map. Measurement statistics are derived
for kicked quantum nondemolition measurements, combined with conditional
unitary operations. These results are applied to derive a feedback protocol to
produce an arbitrary pure state after a weak measurement, as well as to
investigate how an initially mixed state becomes purified with and without
feedback.
