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Science 16 February 2007:
Vol. 315. no. 5814, pp. 966 - 968
DOI: 10.1126/science.1136303
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Reports

Experimental Realization of Wheeler's Delayed-Choice Gedanken Experiment

Vincent Jacques,1 E Wu,1,2 Frédéric Grosshans,1 François Treussart,1 Philippe Grangier,3 Alain Aspect,3 Jean-François Roch1*

Wave-particle duality is strikingly illustrated by Wheeler's delayed-choice gedanken experiment, where the configuration of a two-path interferometer is chosen after a single-photon pulse has entered it: Either the interferometer is closed (that is, the two paths are recombined) and the interference is observed, or the interferometer remains open and the path followed by the photon is measured. We report an almost ideal realization of that gedanken experiment with single photons allowing unambiguous which-way measurements. The choice between open and closed configurations, made by a quantum random number generator, is relativistically separated from the entry of the photon into the interferometer.

1 Laboratoire de Photonique Quantique et Moléculaire, Ecole Normale Supérieure de Cachan, UMR CNRS 8537, 94235 Cachan, France.
2 Key Laboratory of Optical and Magnetic Resonance Spectroscopy, East China Normal University, 200062 Shanghai, China.
3 Laboratoire Charles Fabry de l'Institut d'Optique, Campus Polytechnique, UMR CNRS 8501, 91127 Palaiseau, France.

* To whom correspondence should be addressed. E-mail: roch{at}physique.ens-cachan.fr

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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