The quantum Zeno effect - evolution of an atom impeded by measurement

The evolution of a quantum system is supposed to be impeded by measurement of an involved observable. This effect has been proven indistinguishable fr om the effect of dephasing the system's wave function, except in an individ ual quantum system. The coherent dynamics, on an optical E2 line, of a sing le trapped ion driven by light of negligible phase drift has been alternate d with interrogations of the internal ion state. Retardation of the ion's n utation, equivalent to the quantum Zeno effect, is demonstrated in the stat istics of sequences of probe-light scattering 'on' and 'off' detections, th e latter representing back-action-free measurement. (C) 2000 Published by E lsevier Science B.V. All rights reserved.