Caveat: I'm not a physicist and am a little fuzzy on what exactly what I'm asking here. But I'm hoping someone smarter than me can at least clarify (or dismiss) the question as stupid... :)

This question regards the EPR paradox (aka. "spooky action at a distance").

The supposed "paradox" is that, in one view, information (particle spin) "appears" to travel faster than the speed of light.

First, to me the description of the "paradox" is misleading. The paradox does not occur when either particle's spin is measured; it only occurs if and when the two people measuring the spins reunite to compare notes. If they measure their particles and never meet again, there is no apparent paradox.

In other words, to conduct any experiment confirming involving "spooky action at a distance", information must travel in a complete loop in spacetime:

  ^                   |
  |                  (*) reunited
  |                 /   \
Time               /     \
                  /       \
                 /         \
                /           \
     measure   /             \     measure
   particle 1 (*)             (*) particle 2
               \             /
                \           /
                 \         /
                  \       /
                   \     /
                    \   /
                     (*) entangled

So this brings up the question, could QM's prediction of the outcome of this experiment be reformulated in a more natural way, based on viewing the entire "loop", that doesn't seem so "spooky"?

What if, instead of QM stipulating that the particles are "entangled" and somehow will magically know how each other is measured, we instead simply say that QM stipulates certain restrictions on information traveling around any loop in space time.

If so this stipulation and behavior would likely be invariant to the direction of time. In other words, from a QM point of view, traveling backward in time, you could view the reuniting event as the "entanglement" and the original entanglement point as the "reuniting", with the same apparent outcome (spin "measurements" appearing to agree just so).

Part two of this is: what would the "certain restrictions on information traveling around any loop in space time" be?

I know this is vague. I guess my question is are there any interpretations of QM related to this idea, vague as it is?

  • $\begingroup$ Cramer's transactional interpretation seems to fit the bill. $\endgroup$ Sep 20 '18 at 19:07
  • $\begingroup$ Your diagram supposes that there is only one path for information to be reunited. But actually the whole intersection of the future light cones originating from the measurement events is the region were the fact that the measurements are correlated can have causal effects. So it is not a simple loop. Have a look at Cramer's interpretation anyway, it should interest you IMO. $\endgroup$ Sep 20 '18 at 19:19
  • $\begingroup$ Thanks for the link. Regarding "loops", yes I agree you'd have to generalize the idea to something like "any manifold through which some chain of causality can flow in a closed loop". But at the end of the day what's important is that two chains of causality originate from the same place, separate, and then meet again. $\endgroup$
    – Archie
    Sep 21 '18 at 14:14

Where you're misleading: The entanglement phenomenon is inherent to the entangled particles whether you measure each one or not, there properties remain entangled to each other. There inherent connection is independent of any measurement.

We do measurements on both the particles if we want to varify the phenomenon.

If We already know that the given two particles are an entangled pair, then we only need to measure one of the particle's state and other particle's state will be known automatically without measurement on this other particle.

  • $\begingroup$ It seems a bit fast & loose to say you "know" the other particle's state. If this is just shorthand for saying you know the outcome of certain experiments that you might conduct, then yes that makes sense (otherwise wouldn't you be making some implicit assumptions about the "correct" QM interpretation?). But such experiments always involve a closed loop, so what we "know", i.e., the QM rules of entanglement, could (conceivably) be restated as a rule about information flowing in loops. $\endgroup$
    – Archie
    Sep 21 '18 at 14:11
  • $\begingroup$ No. I'm not making any implicit assumptions regarding the "correct" QM interpretation. I only mean that the loop of measurement you're talking about is nonsense. As i already told you above that the phenomenon is independent on any measurement. By measurement(which is active in nature) we are just decohering the superposition state to one of the state of that first particle. This automatically leads to decoherence of other particle state. If you're interested in Interpretation, in one of the paper published by a MIT group they claim that this two particles must be connected with a wormhole. $\endgroup$
    – Aman pawar
    Sep 21 '18 at 15:04
  • $\begingroup$ If you want to know more, see the paper by searching on google. $\endgroup$
    – Aman pawar
    Sep 21 '18 at 15:05

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