Comment on “photons can tell ‘contradictory’ answer about where they have been”

Gregory Reznik, Carlotta Versmold*, Jan Dziewior, Florian Huber, Harald Weinfurter, Justin Dressel, Lev Vaidman

*Corresponding author for this work

Research output: Contribution to journalComment/debate


Yuan and Feng (Eur. Phys. J. Plus 138:70, 2023) recently proposed a modification of the nested Mach–Zehnder interferometer experiment performed by Danan et al. (Phys. Rev. Lett. 111:240402, 2013) and argued that photons give “contradictory” answers about where they have been, when traces are locally imprinted on them in different ways. They concluded that their results are comprehensible from what they call the “three-path interference viewpoint,” but difficult to explain from the “discontinuous trajectory” viewpoint advocated by Danan et al. We argue that the weak trace approach (the basis of the “discontinuous trajectory” viewpoint) provides a consistent explanation of the Yuan–Feng experiment. The contradictory messages of the photons are just another example of photons lying about where they have been when the experimental method of Danan et al. is applied in an inappropriate setup.

Original languageEnglish
Article number181
JournalEuropean Physical Journal Plus
Issue number2
StatePublished - Feb 2024


FundersFunder number
National Science Foundation1915015
Deutsche Forschungsgemeinschaft2016/23/G/ST2/04273, 38144572, EXC-2111 390814868
United States-Israel Binational Science Foundation735/18
Israel Science Foundation2064/19


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