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arXiv · 1701.04109

An Improved Experiment to Determine the `Past of a Particle' in the Nested Mach-Zehnder Interferometer

Alon Ben-Israel·Lukas Knips·Jan Dziewior·Jasmin Meinecke·Ariel Danan·Harald Weinfurter·Lev Vaidman
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Abstract

We argue that the modification proposed by Li et al. [Chin. Phys. Lett. 32, 050303 (2015)] to the experiment of Danan et al. [Phys. Rev. Lett. 111, 240402 (2013)] does not test the past of the photon as characterised by local weak traces. Instead of answering the questions: (i) Were the photons in A? (ii) Were the photons in B? (iii) Were the photons in C? the proposed experiment measures a degenerate operator answering the questions: (i) Were the photons in A? (ii) Were the photons in B and C together? A negative answer to the last question does not tell us if photons were present in B or C. A simple variation of the modified experiment does provide good evidence for the past of the photon in agreement with the results Danan et al. obtained.

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Alon Ben-Israel, Lukas Knips, Jan Dziewior, Jasmin Meinecke, Ariel Danan, Harald Weinfurter, Lev Vaidman. 2017-01-15. An Improved Experiment to Determine the `Past of a Particle' in the Nested Mach-Zehnder Interferometer. https://doi.org/10.1088/0256-307x%2F34%2F2%2F020301

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