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Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality

Robens, Carsten; Alt, Wolfgang; Emary, Clive; Meschede, Dieter; Alberti, Andrea


Carsten Robens

Wolfgang Alt

Clive Emary

Dieter Meschede

Andrea Alberti


Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the “bomb test” with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett–Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett–Garg inequality.


Robens, C., Alt, W., Emary, C., Meschede, D., & Alberti, A. (2017). Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality. Applied physics. B, Lasers and optics, 123(1), Article 12.

Journal Article Type Article
Acceptance Date Nov 4, 2016
Online Publication Date Dec 19, 2016
Publication Date Jan 1, 2017
Deposit Date Jun 28, 2018
Publicly Available Date Oct 27, 2022
Journal Applied Physics B
Print ISSN 0946-2171
Electronic ISSN 1432-0649
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 123
Issue 1
Article Number 12
Public URL
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© The Author(s) 2016<br /> Open Access<br /> This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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