That queer experiment; what is its limit?

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Discussion Overview

The discussion centers around the limits of a quantum experiment where a light beam appears to take two paths simultaneously. Participants explore the potential for extending the distance over which this phenomenon can be observed, particularly in relation to entanglement experiments and the delayed choice experiment.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant references an experiment where a light beam seems to take two paths and questions if there is a limit to how far this can be observed, suggesting a distance of 1 km.
  • Another participant recalls that there have been entanglement experiments conducted over similar distances but advises caution in quoting this information.
  • A different participant asserts that theoretically, there should be no upper limit to the distance, referencing the delayed choice experiment and the implications of measurement choices on photon behavior over vast distances.
  • Some participants express a desire for links or references to long-distance experiments related to this topic.
  • Links to several papers are provided by a participant, which may contain relevant information on long-distance quantum experiments.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the existence of limits for the experiment, with some suggesting there may be none while others seek empirical evidence or references to support their claims.

Contextual Notes

The discussion includes references to theoretical concepts and experimental setups that may not be universally agreed upon or validated, highlighting the speculative nature of the claims made.

EroticNirvana
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Some of you may have heard of this experiment:

http://www.cs.caltech.edu/~westside/quantum-intro.html


I'm thinking of the experiment at the top of the page where the light beem seems to take two paths.

Does anyone know whether there is a limit for how far you can let this beem "travel in both directions". E.g. we might try to let the beem travel 1km.
 
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come on, someone please help me out!
 
IIRC there have been entanglement experiments with distances of that order. Don't quote me on this though.
 
No, theoretically there shouldn't be any upper limit. In the context of something called the "delayed choice experiment", I've often seen the suggestion that an astronomer could, depending on her choice of measurement, determine whether a photon emitted millions of years ago behaves as though it took a single path around a galaxy or whether it behaves as though it took both paths at once--see the section entitled 'Does our choice "change the past"?' from this page on the delayed-choice experiment. I don't know whether an experiment of this type has actually been performed, though.
 
got link?

inha said:
IIRC there have been entanglement experiments with distances of that order. Don't quote me on this though.

Thx. If anyone´s got a link or reference to such a "long distance" experiment I´d be very thankful.
 
EroticNirvana said:
Thx. If anyone´s got a link or reference to such a "long distance" experiment I´d be very thankful.
http://arxiv.org/PS_cache/quant-ph/pdf/9707/9707042.pdf

http://arxiv.org/PS_cache/quant-ph/pdf/9806/9806043.pdf

http://www.gap-optique.unige.ch/Publications/Pdf/Optics98.pdf
 
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