Issue Eur. Phys. J. D Volume 14, Number 3, June 2001 Page(s) 387 - 396 Section Quantum Optics and Quantum Information DOI 10.1007/s100530170207

Eur. Phys. J. D 14, 387-396

What does an observed quantum system reveal to its observer?

P.E. Toschek and Ch. Wunderlich

Institut für Laser-Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany

toschek@physnet.uni-hambourg.de

(Received 11 January 2001 and Received in final form 28 February 2001)

Abstract
The evolution of a quantum system under observation becomes retarded or even impeded. We review this "quantum Zeno effect"in the light of the criticism that has been raised upon a previous attempt to demonstrate it, of later reexaminations of both the projection postulate and the significance of the observations, and of the results of a recent experiment on an individual cold atom. Here, the micro-state of the quantum system gets unveiled with the observation, and the effect of measurement is no longer mixed up with dephasing the object's wave function by the reactive effect of the detection. A procedure is outlined that promises to provide, by observation, an upper limit for the delay of even an exponential decay.

PACS
03.65.Bz - Foundations, theory of measurement, miscellaneous theories (including Aharonov-Bohm effect, Bell inequalities, Berry's phase).
32.80.-t - Photon interactions with atoms.
42.50.Ct - Quantum description of interaction of light and matter; related experiments.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001

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