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Phys. Rev. Lett. 74, 4763 - 4766 (1995)

Interaction-Free Measurement

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Paul Kwiat, Harald Weinfurter, Thomas Herzog, and Anton Zeilinger
Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria

Mark A. Kasevich
Department of Physics, Stanford University, Stanford, California 94305

Received 19 September 1994

We show that one can ascertain the presence of an object in some sense without interacting with it. One repeatedly, but weakly, tests for the presence of the object, which would inhibit an otherwise coherent evolution of the interrogating photon. The fraction of “interaction-free” measurements can be arbitrarily close to 1. Using single photons in a Michelson interferometer, we have performed a preliminary demonstration of some of these ideas.


©1995 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevLett.74.4763
DOI: 10.1103/PhysRevLett.74.4763
PACS: 03.65.Bz, 42.50.Dv

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