Hardy's Paradox - Which Way Information

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Discussion Overview

The discussion revolves around Hardy's Paradox, specifically exploring the implications of quantum mechanics on the detection of particles and the nature of their paths. Participants examine the experimental setup related to the paradox, focusing on concepts such as superposition, wavefunction collapse, and the realism interpretation in quantum mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the detections available in quantum mechanics indicate the paths taken by the electron and positron, suggesting that they remain in superposition after the beam splitters.
  • Another participant asserts that certain phenomena can only occur if the wavefunction collapse is instantaneous.
  • A participant references a paper proposing that it is possible to distinguish between instantaneous collapse and finite-time reduction through double measurements of polarization, noting that the results would show distinct behaviors in each scenario.
  • Further discussion indicates that the findings from the referenced paper suggest compatibility of instantaneous collapse with quantum mechanics, contrasting it with time-finite collapse.
  • One participant acknowledges the profound implications of the findings discussed in the paper.

Areas of Agreement / Disagreement

Participants express differing views on the nature of wavefunction collapse and its implications for quantum mechanics, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

The discussion includes references to specific experimental setups and theoretical interpretations, but lacks consensus on the implications of wavefunction collapse and the nature of particle interactions in the context of Hardy's Paradox.

StevieTNZ
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I have three quick questions regarding the experimental set-up attached, in relation to Hardy’s Paradox.

What possible detections are available, according to Quantum Mechanics, and do those detections indicate, for the electron and the positron, which path they took? I’m guessing not as at the beam splitters, there is ½ probability of being reflected and ½ probability of being transmitted. In accord with QM, are they are in a superposition, after the beam splitter, as being both reflected and transmitted?

Because the particles in question are in a superposition of being in both paths (e+ in a superposition of paths u+ and w+/u+, and e- in a superposition of paths v- and w-/u-), they’re strictly not ‘real’ (this is where the realism refutation comes about, in standard QM), thus the particles cannot interact and annihilate?
 

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that stuff can happen only if the wavefunction collapse is instantaneous.
 
Last edited:
work in progress
http://arxiv.org/abs/1303.2972
"We find that it is possible to discriminate between the scenarios of instantaneous collapse and finite-time reduction via a large number of double measurements of polarization. The quantities to be recorded would present distinct behaviors in each scenario, the deviations being small but distinguishable from pure statistical fluctuations"
 
audioloop said:
work in progress
http://arxiv.org/abs/1303.2972
"We find that it is possible to discriminate between the scenarios of instantaneous collapse and finite-time reduction via a large number of double measurements of polarization. The quantities to be recorded would present distinct behaviors in each scenario, the deviations being small but distinguishable from pure statistical fluctuations"

First draft looks pretty nice, audioloop.
 
It would seem from that paper that instantaneous collapse is compatible with QM - than time-finite collapse - by looking at the two tables they provide results in.
 
Indeed. has profund implications.
 

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