  Quantum measurements are considered for optimal control of quantum dynamics
with instantaneous and continuous observations utilized to manipulate
population transfer. With an optimal set of measurements, the highest yield in
a two-level system can be obtained. The analytical solution is given for the
problem of population transfer by measurement-assisted coherent control in a
three-level system with a dynamical symmetry. The anti-Zeno effect is recovered
in the controlled processes. The demonstrations in the paper show that suitable
observations can be powerful tools in the manipulation of quantum dynamics.
