Does the weak trace show the past of a quantum particle?

Jonte R. Hance*, John Rarity, James Ladyman

*Corresponding author for this work

Research output: Working paperPreprint

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We investigate the weak trace method for determining the path of a quantum particle in an unperturbed system. Specifically, looking at nested interferometer experiments, when internal interferometers are tuned to destructive interference, we show that the weak trace method gives misleading results. This is because the methods used experimentally to obtain the weak value of the position operator necessarily perturb the system, hence, in some cases the assumption that weak coupling being equivalent to no coupling is incorrect. Experiments performed that are claimed to support the interpretation simply show the effects of this coupling acting as measurement, rather than tapping into the underlying reality of what happens in a quantum system when no-one is looking.
Original languageEnglish
Number of pages8
Publication statusSubmitted - 28 Sept 2021

Bibliographical note

8 pages, 2 figures

Structured keywords

  • Centre for Science and Philosophy
  • QETLabs


  • quant-ph
  • physics.hist-ph


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