Quantum entanglement -- information transfer?
471895
This is the kind of question I like ... :-)\n\nNo, this is not information transfer. I will try to enlighten the problem by formulating it more precisely.\n\nBut first, I'd like to show that if you could tranfer information faster than light, you'd get a contradiction with special relativity.\n\nSuppose A can communicate some information faster than light to B. Let A sending the information be event 1, B receiving it event 2. If the message is travelling faster than light, it can be shown that in the reference frame of A, event 1 happens _before_ event 2, while in the reference frame of B event 1 happens _after_ event 2, which is a contradiction because Bob cannot receive the message before Alice sends it. If a light-signal cannot travel between events 1 and 2, we call them spacelike separated (at least in some other languages than English we do :-) ). Spacelike separated events don't have a definite temporal order (the order depends on the reference frame).\n\nOf course, in your example there is a correlation between the outcome of Alice's and Bob's measurement, but it cannot be considered information transfer. They always knew that they would get opposite results, but they didn't know who would get |up> and who would get |down>. Information transfer would mean that Alice already has a piece of data she knows, eg. a bit of 1, and she would like to transfer it to Bob. Bob's gaining knowledge of this information is the result of Alice's sending it. So there is a definite temporal order (and causal relationship) between these events. In the entagled particle-pair example she doesn't have this piece of information before she does a measurement.\n\nHowever, you could say that A can transfer information like this: she does a measurement, and as the result of the measurement the wave function of both particles collapses, and B can measure to see if his particle is in a collapsed (|up> OR |down>) or superposed (|up> + phase_factor*|down>) state. So B will know if A has already measured or not! But B cannot decide which state the particle was in with only one measurement! And he can make only ONE measurement, because the measurement collapses the state. As a result he will always get either UP or DOWN, so he cannot tell if the original state was |up>+|down> or one of |up> or |down>.\n\nOf course if B could copy the state of his particle, he would be able to make multiple measurement on the same quantum-spin-state, but he cannot copy the state because of the no-cloning theorem (Zurek-Wootters, Nature, 1983 if I remember well, but anyway, see it on Wikipedia). Of course, if he would be able to copy the state, we would get a contradiction with special relativity.\n\nAs satanorsanta pointed out there are still problems with the _interpretation_ of quantum mechanics (especially with the measurement postulate), but I wouldn't consider this specific question unsolved.\n\nI know my English is not the best ... I hope you will understand my reasoning. If you's like to chat about these thing, send me a mail.
463641
see\nhttp://hyperphysics.phy-astr.gsu.edu/hbase/surten2.html#c1\n\n here you can find the answer for your question with MATHEMATICAL EXPLANATIONS.
801633
Hi, \n\nThat's too much like real work, but think about it like breaking pool balls in classical, and wave interference with quantum. \n\nHope that helps, \nMatt
1066095
In quantum mechanics, particles are desribed by a quantum state that is characterised by a series of "quantum numbers". A closed system of particles obeys one of two sets of rules, depending on the sort of particle. Entanglement is actually easiest to understand for the class of particles called Fermions (particles like electrons and protons) rather than bosons (particles like photons).\n\nFermions obey a rule that says no two of them in a system can have exactly the same quantum state. Spin is a useful quantum number to use here, because it can have only one of two values for a particle - up or down.\n\nImagine creating a system in a very long box with just two electrons in it, one at either end, that are in their lowest possible energy state. They will be identical in all respects except that one will have spin up and the other spind down. There is no way of knowing which is which.\n\nNow imagine measuring the spin of the electron at one end of the box. Lets say its up. This *must* mean that the spin of the electron at the other end of the box is down. So we have "instantaneously" found out the spin of a remote particle, which relativity (which insists information cannot travel faster than light) says cannot happen. Einstein-Podolsky-Rosen argued that this created a paradox at the heart of quantum mechanics.\n\nThe paradox was resolved experimentally by showing that particles whose states are entangled in the way described above do indeed behave as quantum mechanics predicts. These experiments are often carried out with photons. In this case a single photon is broken down into tow or more photons whose quantum states must clearly add to give the state of the original photon (quantum numbers are preserved). \n\nSo say we split a photon into two new photons that differ in polarisation, and send them off in different directions to person a and person b. Person a measures the polarisation of theirs and instantly knows the polarisation of the one person b got. And this is precisely what happens.\n\nThis does not violate relativity because there is no way that person a can communicate to person b the result of their measurement faster than light, so no information can pass faster than the speed of light. This means if the two arrange to measure their photons as soon as they get them, each has exactly the same 50/50 probability of getting either polarisation.\n\nThis seems paradoxical because it is counter to classical intuitive feelings about how the world works. But classical and intuitive feelings are often unreliable, and experiment has shown that the paradox is not really a paradox but ironically a description of how the world really works.\n\nQuantum entanglement is being research for use in cryptography because it impossible to fiddle with. Lets say I split a load of photons and send half to a and half to b as keys to encrypt a message. When a makes his measurements on the photons he will know the results b will get and so can communicate with b securely. But if anyone tries to intercept the message to say b they will destroy the entanglement. They may get the key, but it is useless because they cannot communicate it to b - ie it will be obvious that there has been an interception.
39599
I would suggest you use wikipedia...\n\nhttp://en.wikipedia.org/wiki/Quantum_mechanics
1182496
Yes it just depends on what you beleive in and what you don't.  This kind of science is called quantum physics.  Check it out some time, it's very interesting.
257269
Sounds like you're asking about a quantum mechanical phenomenon sometimes called "spooky action at a distance."\n\nIn it's most basic form, it involves two "entangled" electrons (or any subatomic particle) If you could separate the pair by some great distance--even light years--and then influence some characteristic of one electron, its distant twin would react instantly to assume the same characteristic.\n\nTry this website for a more complete explanation -->http://www.everything2.com/index.pl?node_id=138524
609706
Your supposition was correct. All information transferred is encrypted. The performance is not as bad as you might think because public key cryptography is only used to securely transfer a symmetric key which allows the data to be transmitted securely and without a lot of overhead.
652835
It is much faster and efficient to transmit information than it is to transport matter. For that reaon, a practical system of teleportation would not transport all your atoms. Instead, it would disassemble you particle by particle, creating a dataset of the pattern. It would then transmit the dataset at the speed of light to your destination, where raw materials are available to reassemble you from the pattern. The raw materials are recycled from others who have been disassembled in the process of teleportation. \n\nAfter teleportation, you will be the same person, with the same memories, knowledge, and personality. The only difference is that you won't consist of the original particles. That should not matter, because all atoms of any element are identical and indistinguishable.
198845
Um ... yes?\n\nHow the heck can we figure this out without links to the relevant information?  Or is reading your mind part of the question requirements?
247190
The patterns are the same.  It doesn't matter if you send the photons through one at a time or many at once.
730142
Possibly so. Possibly no. I'd say the Heisenberg uncertainty principle comes foremost into play here. Maybe also Schrödinger's cat. Is it dead or still alive? That would make a significant difference, you know. These questions can't just be taken so lightly. And how could you even consider Y!A as a forum to resolve such complex issues as this? More to the point, even assuming Planck scale dynamics can be fully understood with the mathematical tools we have at hand today, where exactly does that get us? We still don't know what topping to put on our pizza this weekend. Or whether a third eye would make a good chick magnet. Or even whether that darn cat is still alive or dead.... 'tis an enduring mystery. And we wouldn't want to take all the mysterious challenge out of life, now would we?....Meow.
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how about quantum information theory?  this encompasses some of the cool research that's going on currently, including quantum entanglement, teleportation and the 'quantum parallelism' that you get by using quantum bits in a superposition of states.  \n\nhttp://www.imaph.tu-bs.de/qi/concepts.html\nhttp://www.qubit.org/index.html\nhttp://plato.stanford.edu/entries/qt-entangle/\n\ngood luck!
597088
at the atomic level, there is indeed randomness. you can predict the probabillity that things will occur, but cannot know for sure unless you make a measurement, which messes up the experiment because you "contaminated" the experiment with whatever you used to measure it. for instance, if you shine a flashlight at a double slit, half the light will go through 1 slit and half will go through another. however, if you turn down the output of the flashlight to 1 photon at a time, then the same thing happens. you cannot predict which one it will go through, it is completely random.\n\noh, and quantum theorry has been proven correct, better than any other theory out there - like newtonian physics, which have been shown to be approximations of the more accurate quantum theory.
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Of course information is an important basic concept in physics. I do not understand what you even mean with this question. \n\nFor example, the restrictions that nothing can travel faster than the speed of light only refer to INFORMATION TRANSFER. \n\nThere is a huge field of quantum information theory in physics that is very active. \n\nIf you want to do dimensional analysis, as one does with other dimensional units (essentially using group theoretic principles in studying a problem), I am sure you can devise a scheme using "bits" or some other units of information and do dimensional analysis (for example, one might consider nats, shannons or hartleys; see reference below)
30549
No no in classical model of mathemetics.But in quantum logic one of these problem the factorization problem is solved by the Shor's algorithm..In fact this gave the scientist a new look for the quantum computation.
416146
yes in the quantum world. hey and if no one reads this answer have i really typed it??