  We study the problem of driving a known initial quantum state onto a known
pure state without using a unitary evolution. This task can be achieved by
means of von Neumann measurement processes, introducing N observables which are
consecutively measured in order to approach the state of the system to the
target state. We proved that the probability of projecting onto the target
state can be increased meaningfully by adding suitable observables to the
process, that is, it converges to 1 when N increases. We also discuss a
physical implementation of this scheme.

Quantum Physics