Perfect Zeno effect through imperfect measurements at a finite frequency*

The quantum Zeno effect (QZE) is usually thought to require infinitely frequent and perfect (i.e., projective) measurements to freeze the dynamics of quantum states. We show that perfect freezing of quantum states can also be achieved by more realistic non-projective measurements performed at a finite frequency. Furthermore, we show that, in the case of qubits, in contrast to the usual QZE, the state freezing via imperfect measurements can be adjusted to preserve arbitrary states in the Bloch sphere.