EPR and Non-Locality - For and Against

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The forum discussion centers on the debate surrounding the necessity of non-locality in quantum mechanics (QM) and its relationship with quantum field theory (QFT). Participants argue that QM does not require non-locality, citing the cluster decomposition property as a key principle. They reference Stephen Boughn's work and discuss the implications of Bell inequalities, emphasizing that while QFT is constructed to be local, the interpretations of entanglement and correlations challenge this notion. The conversation highlights the semantic complexities of terms like "non-locality" and "entanglement," advocating for clarity in definitions.

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  • #151
I am not educated in QM, so this post is to ask a few questions related the the non-locality/entanglement controversy for which I am hoping for a simple answer.

As I understand an example of the entanglement part, what appears to two observers is two partcles having a combined propery that their spin directions are opposite. If there are two devices far apart, each positionsed to test spin with respect to the same axis direction. When each of these two particles arrive at its target device, its spin will be determined, and when both spins are determined it will be found that they have opposite spins.

Assume that there is a clock associated with each device, and the clock times are synchronized, so that the determination of each measured spin is associated with a specific time.

Assume the two devices are separated by a distance D, and that the two times related to the devices determining a spin value differ by a time T. Therefore this result might be interpreted as the the ealier spin determination influences the later spin determination and the influence traveled at a speed of D/T, and the configuration might well be that D/T > c.

I think I understand that the transmission of influence does not in any way permit an observer to predict the spin of the second particle before the particle arrives at its devise.

My question is the following. Does the influence from the location of one device determining a spin value and the second devise determining a spin value constitute a transmission of information? That is, is influence information? Also ,is this a controversial question?

If one defines the transmission of influence to NOT be a transmission of information, then no information has traveled faster than c. Would this mean that there is not any non-locality issue? If not, why not?
 
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  • #152
Buzz Bloom said:
Does the influence from the location of one device determining a spin value and the second devise determining a spin value constitute a transmission of information?

Not by any definition of "information" that I am aware of.

Buzz Bloom said:
If one defines the transmission of influence to NOT be a transmission of information, then no information has traveled faster than c. Would this mean that there is not any non-locality issue?

As I have said umpteen times now in this thread, it depends on what you mean by "non-locality". There is not a single accepted meaning for that term. So questions like this do not have single well-defined answers.
 
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  • #153
Since we are going in circles this thread is closed. In the future, everyone please remember to be clear about what you mean by ambiguous terms
 

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