Would it be possible to take advantage of "Spooky Action at a Distance" to build an FTL communicator?
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Would it be possible to take advantage of "Spooky Action at a Distance" to build an FTL communicator?
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Let me elaborate.
Since quarks have been observed to instantly change to match their partner no matter what the distance, would it be possible to design a stringed code of quarks, trap them and their partners in separate "quark storage units," and use them to communicate?
I'm not asking about the process of capturing and preserving quarks, that's sci-fi. But if we change set A to read 0101001, set B should instantly change to 1010110 and there would be the basis for a message code that could traverse interstellar distances instantly!
Faster than Light communications.
Order of Kilopi
As we currently understand the effect, no, it is not possible to communicate via the 'spooky action at a distance' (assuming you're referring to the Bell inequality, entangled states, etc).
There are quite a few good explanations of why it isn't possible - perhaps someone could post a link to their favourite?
Is there a particular reason you chose to put this in th ATM (and not Q&A) section?
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Interesting note: using quantum entanglement almost exactly as described by Faultline is the basis for the "ansible", a FTL communication device in the "Ender's Game" sci-fi series, by Orson Scott Card. It may have appeared in sci-fi before this as well.
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I put it here in ATM because it seems as though it should be possible, so I have my own preconceived notions about the answer.
Order of Kilopi
Ursula Le Guin? Left Hand of Darkness, The Dispossessed, ...Originally Posted by Tassel
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Even if it were one quark in each "box" that could be taken to a distant star, with two states that could be determined by analysis, it seems as though you could have a simple communicator that could say "0" or "1", positive or negative, yes or no, one if by land, two if by sea, etc...
If you could control it more rapidly, you could string a binary code out of it. Why would this not be possible?
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Because the changes are completely random.
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Is it completely random? Or is there a pattern that we just don't understand yet. It could be just a tough code to crack.
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Yep, it's completely random, totally random, more random than the ugliest string of random characters you can think up.
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i've always understood this to be because in order to register the bit state on the receive end, you must first observe it. in doing so, you change its state, randomly per the whole schroedinger's cat mess. therefore, you can never know what was sent as the observed state has a 50% chance of being wrong.
is this the randomness you all are referring to? as well, is my description correct? it has been a while since atomic physics (a-bomb we undergrads called it).
taks
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I agree and, because of the random nature of the effect, we can not know that a "spooky" instant, non-local communitation has taken place until after we compare the signal at the sending end with the signal at the receiving end and that comparison can not be made at anything greater than light speed.
Last edited by Nereid; 2005-Oct-29 at 05:07 PM. Reason: fixed [ quote ] tags
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So it depends on being able to force the change of the distant quark by changing the local quark in a predictable manner. How has the change been determined to be completely random? What experiments have been done to make this a fact?
From a numbers standpoint, pure randomness should really be unattainable, like complete and total entropy.
I'm rambling now, grasping at straws. Has there been any research into the nature of the 'random' change in state?
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You asked for a link about this; here is a good one
- the section called 'Bell's Telephone'
http://www.imaph.tu-**.de/qi/lecture/qinf11.html
Tensor product Hilbert space eh?It should be mentioned that we do not really have to resort to the Theory of Relativity to find the impossibility of Bell's Telephone. Quantum Theory or, more precisely, the standard way of describing composite systems in a tensor product Hilbert space rules out Bell's Telephone, too. So Bell's Telephone is also properly an "impossible machine of quantum mechanics".
(absolutely no idea what that is...)
but if you read this link with an optimistic frame of mind, you might notice the last part...
If these non-local hidden variable theorists are right, perhaps we can have our 'ansible'. All we need is a Shevek to write the theory...Of course, nobody can be forced to accept Einstein causality as a fundamental principle. To someone like that our impossibility proof for all the devices above will hardly be convincing. And indeed there is a large community of hidden variable theorists who suggest modifications of quantum mechanics discarding causality, or "locality".
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If they succeed, no doubt all kinds of weird and wonderful things become possible ... perhaps pictures of me falling into a black hole, taken by my friendly ansible-cam that is accompanying me on my fall (it's an SSMBH, so the 'tidal forces' don't smear me to a monolayer on the way in)?
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You can go first if you like; I'll watch.
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This is a good conversation. Would the ability to communicate information instantly over distance violate causality?
Two starships orbit a massive star, one at 10 AU's and one at 100. The first one sees the star beginning to go supernova and transmits, using the spooky phone, to the other starship to tell them to get the heck outta here.
Does that mean that the second, more distant starship has violated any fundamental physical laws by knowing the outcome of an event that hasn't happened yet from their point of view?
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Would the star scenario be any different than someone notifying you that a missle has been launched at location x and instructing you to leave location y? Just because it hasn't been observed by you, does not mean that it has not occured. I view this scenario much like thunder, just because sound doesnt travel "instantly" doesn't mean that the lightning strike doesn't occur until it, or its result, is observed. So how can transmitting faster than light violate causality?
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Yes, it violates causality. One can find circumstances where the second ship would get information before the first ship sent it.
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A situation where one information path has v < c isn't the same. The scenario that shows superluminal signals to violate causality has multiple observers.
Banned
Fascinating.
If this 'instantaneous action at a distance' phenomenon is possible, does it have any implications for GR?
Edit: Oooops, I guess that is what is being discussed above re. causality and stuff.
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It would definitely throw some monkeys into the proverbial gears.
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hehe
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Wouldn't this spooky action alone then violate causality? In certain time frames couldn't it seem that the incoherent recieved action occured before it was sent? If that "is" the case, then how can a spooky action as described above even exist?
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You can't actually transmit the information about the action faster than c.
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So, in that case, the particles themselves don't count as receivers of information. When one changes, the other changes instantly regardless of distance, proven by Bell's Experiment.
Why does a particle not count as a receiver of information?
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There is a sense in which it does. That's part of what makes it spooky. However, we can only see the effect as a better-than-it-should-be correlation of events which are otherwise completely random. So, you know there must have been some influence, but the outcome of the measurement was random anyway, so how can there have been a direct cause for it come out the way it did? Does that make sense? Einstein would have been quite unhappy with this resolution of the EPR paradox, I think, but that appears to be the way the universe works.
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When you observe one of the two coupled particles, you cause the Schrödinger Wave Function to collapse, and the particle must choose a certain state. You have no influence on the state which is chosen. Instantaneously, the partner's particle state is set. It's wave function has also collapsed. It is not the transmission of information, however, because you have no control over it and can't do a thing with it.
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Two ships take a quark with them, each in an opposite direction, and they end up being 1 light-year apart at the instant that one ship observes its particle and forces it to take a "state."
Doesn't the other particle in the pair instantly take a state also? In other words, the ship with the other particle would know the exact moment that the other ship used their equipment to observe the particle?
That's information! One if by land, two if by sea!
Order of Kilopi
How do you know if the particle you're looking at is in a specific state or not? The only way you can do that is by measuring that attribute, and you already know that it's going to be in one state or the other as soon as you measure it, whether the people in the other ship have measured theirs or not.
Say you're trying to use the spin of the particle in some direction. All you can do at your end is measure the particle and find out whether it's spin up or spin down. No matter what they do on the other ship, it's always going to have equal chances for either. How does that help you communicate?
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