How does QFT address the problem of Locality in Quantum Entanglement?

  • Thread starter Soumya_M
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  • #1
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Quantum Entanglement allows spatially separated entangled particles to have impact on each other instantly (overcoming the allowed speed-limit of causal influence which is 'c'). How does Quantum Field Theory address this problem (protecting causality and chronology)?
 

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  • #2
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No information can be transported at speeds greater than c using entanglement. This is stated clearly in nearly every authoritative treatment of the subject, yet we still get loads of people asking this same question.

There is no conflict with SR.
 
  • #3
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No information can be transported at speeds greater than c using entanglement.

What you said about information transfer is allright. But what about the "causal influence". I mean, when one of the entangled particles is measured, it has an "effect" on the other particle (instantly). The measurement of the first particle, "causes" this impact. So the two events (1. measurement of the first particle and 2. impact on the second particle) can be said to be causaly related (event '1.' being the cause and event '2.' its effect). So although there is no instant transfer of information, the "causal influence" does seem overcome the speed limit of 'c'. This is what begs explanation.
 
  • #4
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Faster-than-light 'causal influence' is certainly one possible explanation for the correlations found in the Aspect and subsequent experiments.

I'm not qualified to say any more so I'll leave it there.
 
  • #5
PAllen
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What you said about information transfer is allright. But what about the "causal influence". I mean, when one of the entangled particles is measured, it has an "effect" on the other particle (instantly). The measurement of the first particle, "causes" this impact. So the two events (1. measurement of the first particle and 2. impact on the second particle) can be said to be causaly related (event '1.' being the cause and event '2.' its effect). So although there is no instant transfer of information, the "causal influence" does seem overcome the speed limit of 'c'. This is what begs explanation.

Two points:

1) If you call the measurements A and B, which occurred first is frame dependent.

2) I prefer to think that there is no causality involved at all. There is a feature of reality that two measurements will have a particular relationship with each other. Neither caused the other (you can't talk about which came first). As soon as you see one measurement you know about the result of the other, but there is no causal influence, just correlation built into a non-local quantum state.
 
  • #6
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PAllen said:
If you call the measurements A and B, which occurred first is frame dependent.
True.
Doing the Aspect experiment involves some very precise time measurement, in order to set up a frame in which simultaneity is well defined.

There seems no doubt that something strange is happening, but maybe it's not appropriate for this sub-forum.
 

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