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I don't believe this is a duplication (either that or I didn't understand the answers to the other questions). I understand when sending information via radio waves that the frequency or amplitude is altered to form binary code. So, how would the entangled particles be used in a transfer of information? Furthermore, to send large amounts of data, would vast numbers of particles need to be entangled, or could the manipulation of one pair of particle be sufficient?

ACuriousMind
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Curious Layman
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  • I am sure that if I knew more about the symbols used, that would helpful. Unfortunately, I do not and therefore they are not. I don't understand how an entangled pair of particles becomes a qubit. I see how a stream of particles can be varied in order to transmit data, bit not how a single particle can be varied to transmit data. – Curious Layman Mar 15 '15 at 01:20
  • I fear that if you do not understand bra-ket notation or, more generally, don't have a firm grasp on quantum mechanics, you won't get much use out of answers here, either, but I could be wrong. – ACuriousMind Mar 15 '15 at 01:23
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    You cannot use quantum entanglement (by itself) to send information. – WillO Mar 15 '15 at 01:34
  • I was reading some other things and believe I understand now. Basically, each particle has state of being that can be assigned a number value (e.g. binary). When the state of one particle is changed, the distant particle also changes. The nearby particle's state is altered to represent 1 or 0 (for simplicity). Then, the state of the distant particle changes accordingly, giving the number of 1 or 0. Is that kind of close? – Curious Layman Mar 15 '15 at 02:23
  • @ACuriousMind I think the BB84 protocol relies on the uncertainty principle but not entanglement? Alice can prepare known states, there doesn't seem to be any need for her to make measurements. – adipy Mar 15 '15 at 02:49
  • @adipy: Sorry, you are correct. A better starting point is probably quantum teleportation. – ACuriousMind Mar 15 '15 at 02:53
  • @JimmyG. The thing is, you can't control the outcome when measuring your nearby particle, giving you no control over the distant particle. Also, once the first measurement is made, the entanglement is broken and further measurements will not be correlated. So you can't send a message, but you can share a random bit sequence, and it takes on the order of one particle per random bit. – adipy Mar 15 '15 at 03:05
  • they cannot send information – Jimmy360 Mar 15 '15 at 03:06
  • @adipy How is the state measured that destroys the entanglement? And now that you say that, the whole possibility of instant communication via entanglement seems like a useless field. It seems like our time would be better spent first learning to control the state of the particle and preserving the entanglement. Otherwise, all entanglement is good for is saying "Hah Einstein! Never send info superluminally. Showed you." Beyond that, I don't see the practical applications. – Curious Layman Mar 15 '15 at 03:28
  • Jimmy, this is really a duplicate of your other question .. "tell me more about the spooky stuff!" http://physics.stackexchange.com/questions/170454/is-there-any-theoretical-limit-to-the-distance-at-which-particles-can-remain-ent i don't think anyone blames you for asking this over and over :) I certainly ask it over and over. – Fattie Mar 15 '15 at 03:49
  • Jimmy -- as a starter, suggest you simply google every "entanglement" and "spooky..." QA on this site, and enjoy reading! You'll get a fun grounding that way – Fattie Mar 15 '15 at 03:50
  • @JoeBlow I don't think this is a duplicate of that other question at all. This one asks how information is sent via quantum entanglement and that one is whether or not there is a theoretical limitation on the distance between entangled pairs. – Curious Layman Mar 15 '15 at 03:55
  • Thery're both (fascinating) general beginners questions on "entanglement wonders". There are 100s and 100s of such questions on here. Enjoy reading them! – Fattie Mar 15 '15 at 03:59
  • Just in general ..... "would vast numbers of particles need.." yeah whatever you're doing you need at least one particle for one bit. But note that a speck of dust contains vast vast vast numbers of particles! You're question is like asking "on an SSD drive, do you need vast numbers of elements?" well yeah -- terabytes of them. Incredibly, unbelievably, large numbers. But it's a non-issue, matter has vast numbers of particles -- SSDs cost a few dollars. Recall however that you can't send information using entanglement, it's a misconception – Fattie Mar 15 '15 at 04:03
  • The act of measuring an observable always destroys information about the incompatible observables. (eg, measuring position destroys momentum information) Quantum computing remains a potential application of entanglement, and entanglement also shows us that the randomness inherent to QM can't be explained by local hidden variables. See the CHSH Inequality (a version of Bell's Inequality) – adipy Mar 15 '15 at 04:45

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