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Entropy 2018, 20(7), 538;

When Photons Are Lying about Where They Have Been

Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel
Theory Center, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
Author to whom correspondence should be addressed.
Received: 1 June 2018 / Revised: 15 July 2018 / Accepted: 16 July 2018 / Published: 19 July 2018
(This article belongs to the Special Issue Emergent Quantum Mechanics – David Bohm Centennial Perspectives)
PDF [849 KB, uploaded 19 July 2018]


The history of photons in a nested Mach–Zehnder interferometer with an inserted Dove prism is analyzed. It is argued that the Dove prism does not change the past of the photon. Alonso and Jordan correctly point out that an experiment by Danan et al. demonstrating the past of the photon in a nested interferometer will show different results when the Dove prism is inserted. The reason, however, is not that the past is changed, but that the experimental demonstration becomes incorrect. The explanation of a signal from the place in which the photon was (almost) not present is given. Bohmian trajectory of the photon is specified. View Full-Text
Keywords: past of the photon; Mach–Zehnder interferometer; Dove prism; photon trajectory past of the photon; Mach–Zehnder interferometer; Dove prism; photon trajectory

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Vaidman, L.; Tsutsui, I. When Photons Are Lying about Where They Have Been. Entropy 2018, 20, 538.

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