ATOMIC QUANTUM ZENO EFFECT FOR ENSEMBLES AND SINGLE SYSTEMS

The so-called quantum Zeno effect is essentially a consequence of the projection postulate for ideal measurements. To test the effect, Itano et al. have performed an experiment on an ensemble of atoms where rap idly repeated level measurements were realized by means of short laser pulses. Using dynamical considerations, we give an explanation why th e projection postulate can be applied in good approximation to such me asurements. Corrections to ideal measurements are determined explicitl y. This is used to discuss how far the experiment of Itano et al. can be considered as a test of the quantum Zeno effect. We also analyze a new possible experiment on a single atom where stochastic light and da rk periods can be interpreted as manifestation of the quantum Zeno eff ect. We show that the measurement point of view gives a quick and intu itive understanding of experiments of the above type, although a finer analysis has to take the corrections into account.