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As I understand it (from a lay physics perspective), quantum entanglement has been experimentally demonstrated - it is a reality. As I understand it, you can measure something like the spin of an electron and know that its entangled pair will, in that same instant, no matter where in the universe it is, have the opposite spin.

This would not seem to have any utility as the foundation of a superluminal communications device. Is this true, or has it been established that is there some aspect of quantum entanglement that can ultimately lead to the development of such a device.

In other words: is superluminal communication via quantum entanglement an open scientific question, has it been settled as an impossibility, or is it currently more of an engineering problem than a scientific one?

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You're not the first to ask this question. For a discussion, see – Danu Sep 21 '13 at 20:46
Not sure that's helping me. Plenty of discussion on pre-existing states vs "spooky action at a distance" as the underlying phenomenon. Either way, the scope of entanglement seems to be limited in that nothing is said about influencing the state of a particle such that a "receiver" may have its readable state selected by an arbitrarily remote entangled pair "sender". Seems to be more of a purely academic matter rather than one which may or may not lead to a future communications breakthrough. – Anthony X Sep 21 '13 at 21:25
up vote 6 down vote accepted

This 'spooky action at a distance' will not and can not lead to communications technologies. The point is that the correlation between the two states cannot be used for information transmission. The two observers can influence each others' observations, but they can never communicate their own observations to the other superluminally, and thus will have no way of checking who influenced who (before waiting for subluminal information transmission devices), rendering the correlation between the states useless for all communications purposes.

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To rephrase Danu answer, you can not use the correlation of these entangled particles before you have exchanged some information with another (subluminal) device. The main problem comes from the fact that the outcome of a measurement is random, so there is no way to agree beforehand on how to interpret a measurement done by one of the party involved in this superluminal communication.

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In particular, when you measured some outcome, you cannot tell whether it is caused by you measuring the system, or being determined by the other party measuring the system, thus no way to see there's a correlation in between, and hence the outcome cannot be arranged in a way to form information – Secret Apr 7 at 10:03

protected by Qmechanic Apr 29 '14 at 6:48

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