A relaxationless demonstration of the Quantum Zeno paradox on an individual atom

The driven evolution of the spin of an individual atomicion on the ground-state hyperfine resonance is impeded by the observation of the ion in one of the pertaining eigenstates. Detection of resonantly scattered light identifies the ion in its upper ‘‘bright’’ state. The lower ‘‘dark’’ ion state is free of relaxation and correlated with the detector by a null signal. Null events represent the straightforward demonstration of the quantum Zeno paradox. Also, high probability of survival was demonstrated when the ion, driven by a fractionated p pulse, was probed and monitored during the intermissions of the drive, such that the ions evolution is completely documented. 2002 Elsevier Science B.V. All rights reserved.