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

Lookup NU author(s): Dr Clive Emary



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


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.

Publication metadata

Author(s): Robens C, Alt W, Emary C, Meschede D, Alberti A

Publication type: Article

Publication status: Published

Journal: Applied Physics B: Lasers and Optics

Year: 2017

Volume: 123

Pages: 1-12

Print publication date: 01/01/2017

Online publication date: 19/12/2016

Acceptance date: 04/11/2016

Date deposited: 19/12/2016

ISSN (print): 0946-2171

ISSN (electronic): 1432-0649

Publisher: Springer


DOI: 10.1007/s00340-016-6581-y


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