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If I have two "entangled" particles and I know the spin state of every one of them. Then, I change the spin state of one of the particles, will it affect the spin state of the other particle even if it is far away? Also, it turns out that entanglement is actually real and can be used for many things, is this just the result of a false interpretation and understanding of Quantum Mechanics by those who claim it or it can be really done? And if it is real, will it just change our interpretation of GR?

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possible duplicate of Quantum Entanglement - What's the big deal? –  Mostafa Jul 11 '13 at 22:58
    
This is still very unclear and broad (and us closeable), so I'll close it as a duplicate becasue that is indeed one of the ways to interrpet this. I suggest you clarify your question by editing it. –  Manishearth Jul 12 '13 at 5:58
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marked as duplicate by Dilaton, user1504, Manishearth Jul 12 '13 at 5:58

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If I have two "entangled" particles and I know the spin state of every one of them. Then, I change the spin state of one of the particles, will it affect the spin state of the other particle even if it is far away?

This is a misconception. There is no way of changing the state of one particle from an entangled pair by performing operations on the other one. This would imply a violation of relativistic causality, as the tone of the OP's question implies. See the no-signalling theorem.

Also, it turns out that entanglement is actually real and can be used for many things, is this just the result of a false interpretation and understanding of Quantum Mechanics by those who claim it or it can be really done? And if it is real, will it just change our interpretation of GR?

The existence of entanglement is routinely and daily confirmed in quantum optics and atomic physics laboratories and particle accelerators around the world. Macroscopically observable phenomena such as the quantum Hall effect only occur due to quantum entanglement.

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