What would happen in this double slit experiment?

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Discussion Overview

The discussion revolves around a variant of the double slit experiment, specifically addressing the effects of measurement and observation on the formation of an interference pattern when light is used to determine the path of particles. The inquiry explores the implications of an observer being unable to see the measurement while still being able to observe the final results on a screen.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • Tim questions whether an interference pattern would still form if light is shone on the slits to determine the path of particles, but the observer cannot see this measurement.
  • One participant asserts that the interference pattern will form even when photons are emitted one at a time, suggesting that measurement does not necessarily prevent the pattern from emerging.
  • Another participant emphasizes that measurement is related to physical interaction rather than human observation, indicating that decoherence or wave function collapse affects the interference pattern.
  • Tim expresses agreement with the latter point, indicating uncertainty about the implications of measurement on the experiment.

Areas of Agreement / Disagreement

Participants express differing views on the role of observation and measurement in the formation of the interference pattern, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

The discussion involves assumptions about the nature of measurement, the role of decoherence, and the interpretation of quantum mechanics, which are not fully explored or defined.

TimID
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Hi,

I was reading Hawking's "The Grand Design" and I came up with a question I didn't know the answer to. He describes a variant of the two slit experiment with particles where a faint light is shone on the slits to determine which one each particle goes through. Naturally this destroys the interference pattern.

What I was wondering is, if the experiment is set up so that this light is still shone on the slits, but the person observing the experiment is unable to see it (whilst still being able to see the final screen) does the interference pattern form?

Regards,

Tim
 
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It has been experimentally verified that the interference pattern will form even when the source is emitting one photon at a time.
 
Measurement has nothing to do with humans, but with physical interaction. If there was interaction - decoherence - collpase of the wave function, whatever you call it - then the interference pattern is messed up.
 
etamorphmagus: Thanks, that's what I thought, just wasn't sure.
 

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