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Old Sep 6th 2017, 04:34 AM   #1
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Entanglement

If we produce two particles entangled with spin and send one off into space we know that the combination of their spins is zero. However according to QM each particle has a superposition of all possible spins and only adopts a specific value when it (or its entangled twin) is measured.
The implication of this is that the particle can take on any possible spin value at measurement time and it's entangled twin will adopt the appropriate complimentary value.
If, hypothetically, measurement could be carried out without the waveform collapsing, and more than one measurement was carried out, the measurements may provide different results for the same particle.
Also, hypothetically, if both entangled particles were measured at exactly the same time, it would seem that they could both take on the same value.
This is inconsistent with conservation laws, which would imply that it could not happen. However, the only way to resolve this paradox would seem to be that the spin value for each particle is established at the time of entanglement, which is inconsistent with superposition.
Can anyone resolve my dilemma?
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Old Sep 6th 2017, 02:11 PM   #2
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Originally Posted by Quandry View Post
If, hypothetically, measurement could be carried out without the waveform collapsing, and more than one measurement was carried out, the measurements may provide different results for the same particle.
Also, hypothetically, if both entangled particles were measured at exactly the same time, it would seem that they could both take on the same value.
This is inconsistent with conservation laws, which would imply that it could not happen. However, the only way to resolve this paradox would seem to be that the spin value for each particle is established at the time of entanglement, which is inconsistent with superposition.
Can anyone resolve my dilemma?
why is it inconsistent with superposition?
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Old Sep 6th 2017, 03:58 PM   #3
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Originally Posted by kiwiheretic View Post
why is it inconsistent with superposition?
By definition superposition is not a single state.
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Old Sep 6th 2017, 11:39 PM   #4
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I am by no means an expert in QM but I do follow it from time to time. One of the others might like to suggest a better answer than what I have here.

As far as I might understand the EPR paradox and Bell's inequality it seems he ruled out local hidden variables. I don't think he ruled out non-local hidden variables.

Looks like you are also in NZ. How are you enjoying our wet weather?
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Old Sep 7th 2017, 02:02 AM   #5
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When I look at Houston and the Carribean at the moment I am enjoying our 'wet' weather.
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Old Sep 7th 2017, 10:18 AM   #6
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Baffles Me...

The issue of entanglement is one of the odder features of the quantum world.

Two (or more) entangled particles seem to continue to behave as a single quantum entity, regardless of any distance between them.
So when an observation collapses the superposition waveform of one of the entangled particles, it collapses the waveform of all of them, instantly
and not only that but the overall waveform collapse will be such as to satisfy the entanglement balance (e.g. the total spin=0).
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