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

Abstract

The driven evolution of the spin of an individual atomic ion 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 $\pi $ pulse, was probed {\em and monitored} during the intermissions of the drive, such that the ion's evolution is completely documented.