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Quantum Teleportation Achieved over Record Distances

The views expressed are those of the author and are not necessarily those of Scientific American.


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Telescope used in teleportation experiments

The European Space Agency's Optical Ground Station on Tenerife in the Canary Islands was used as a receiver in recent quantum teleportation experiments. Credit: ESA

Two teams of researchers have extended the reach of quantum teleportation to unprecedented lengths, roughly equivalent to the distance between New York City and Philadelphia. But don’t expect teleportation stations to replace airports or train terminals—the teleportation scheme shifts only the quantum state of a single photon. And although part of the transfer happens instantaneously, the steps required to read out the teleported quantum state ensure that no information can be communicated faster than the speed of light.

Quantum teleportation relies on the phenomenon of entanglement, through which quantum particles share a fragile, invisible link across space. Two entangled photons, for instance, can have correlated, opposite polarization states—if one photon is vertically polarized, for instance, the other must be horizontally polarized. But, thanks to the intricacies of quantum mechanics, each photon’s specific polarization remains undecided until one of them is measured. At that instant the other photon’s polarization snaps into its opposing orientation, even if many kilometers have come between the entangled pair.

An entangled photon pair serves as the intermediary in the standard teleportation scheme. Say Alice wants to teleport the quantum state of a photon to Bob. First she takes one member of a pair of entangled photons, and Bob takes the other. Then Alice lets her entangled photon interfere with the photon to be teleported and performs a polarization measurement whose outcome depends on the quantum state of both of her particles.

Because of the link between Alice and Bob forged by entanglement, Bob’s photon instantly feels the effect of the measurement made by Alice. Bob’s photon assumes the quantum state of Alice’s original photon, but in a sort of garbled form. Bob cannot recover the quantum state Alice wanted to teleport until he reverses that garbling by tweaking his photon in a way that depends on the outcome of Alice’s measurement. So he must await word from Alice about how to complete the teleportation—and that word cannot travel faster than the speed of light. That restriction ensures that teleported information obeys the cosmic speed limit.

Even though teleportation does not allow superluminal communication, it does provide a detour around another physics blockade known as the no-cloning theorem. That theorem states that one cannot perfectly copy a quantum object to, for instance, send a facsimile to another person. But teleportation does not create a copy per se—it simply shifts the quantum information from one place to another, destroying the original in the process.

Teleportation can also securely transmit quantum information even when Alice does not know where Bob is. Bob can take his entangled particle wherever he pleases, and Alice can broadcast her instructions for how to ungarble the teleported state over whatever conventional channels—radio waves, the Internet—she pleases. That information would be useless to an eavesdropper without an entangled link to Alice.

Physicists note that quantum entanglement and teleportation could one day form the backbone of quantum channels linking hypothetical quantum processors or enabling secure communications between distant parties. But for now the phenomenon of teleportation is in the gee-whiz exploratory phase, with various groups of physicists devising new tests to push the limits of what is experimentally possible.

In the August 9 issue of Nature, a Chinese group reports achieving quantum teleportation across Qinghai Lake in China, a distance of 97 kilometers. (Scientific American is part of Nature Publishing Group.) That distance surpasses the previous record, set by a group that included several of the same researchers, of 16 kilometers.

But a more recent study seems to have pushed the bar even higher. In a paper posted May 17 to the physics preprint Web site arXiv.org, just eight days after the Chinese group announced their achievement on the same Web site, a European and Canadian group claims to have teleported information from one of the Canary Islands to another, 143 kilometers away. That paper has not been peer-reviewed but comes from a very reputable research group.

Both teams of physicists faced serious experimental challenges—sending a single photon 100 kilometers and then plucking it out of the air is no easy task. In practical terms, both groups’ Alices and Bobs needed laser-locked telescopes for sending and receiving their photons, as well as complex optics for modifying and measuring the photons’ quantum states.

But that’s nothing compared to what the physicists have in mind for future experiments. Both research groups note that their work is a step toward future space-based teleportation, in which quantum information would be beamed from the ground to an orbiting satellite.

About the Author: John Matson is an associate editor at Scientific American focusing on space, physics and mathematics. Follow on Twitter @jmtsn.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. MrJoe 9:53 pm 08/9/2012

    I think they should use this for communication. If the quantum state of two entangled photons is identical regardless of distance, they should put one on Earth and one on Mars and then use the bond as a way to transfer data from one end to the other instantaneously. Then we wouldn’t have to wait the 14 minutes that we currently have to wait for information to travel the speed of light from Mars to Earth.

    Link to this
  2. 2. gotapresent 10:47 pm 08/9/2012

    Read the article more closely, quantum entanglement can’t be use to transmit information faster than light.

    Link to this
  3. 3. kphuser1 2:19 am 08/10/2012

    “First [Alice] takes one member of a pair of entangled photons, and Bob takes the other.” If only there was some way of determining existing entangled states already at a distance.

    Link to this
  4. 4. brentbordelon 4:59 am 08/10/2012

    All things considered, this is really no better than New York Bob pointing a flashlight at Philly Phil, turning it on and off, and Phil seeing it.

    It is, however, a lot more expensive (and a lot cooler sounding).

    Link to this
  5. 5. jtdwyer 8:40 am 08/10/2012

    brentbordelon – Well put!

    Using this capability, though, your satellite message content might be encoded by a secured key, preventing your pay-per-view TV signals from being intercepted…

    Link to this
  6. 6. HowardB 1:25 pm 08/10/2012

    I really despair of the continued tabloidisation of SciAm when I read headlines like this.

    “The experiments could pave the way for ground-to-space quantum teleportation”

    In what way exactly can this be called ‘paving the way’ ?

    Link to this
  7. 7. Quantum Ghost 1:46 pm 08/10/2012

    This does indeed sound amazing. If I understand this correctly, and I’m not sure if i do, what seems to be stopping information traveling faster than light speed is that the receiver must await word from the sender about the configuration of the first photon-or any particle. So to overcome that obstacle the “word” must arrive before the operation begins. I wonder if telling receiver how the initial particle will be configured before it is would allow faster than light information transport.

    Can anyone who reads this please respond to it. I like to know how people view my opinion.

    Link to this
  8. 8. davefrancis 3:45 pm 08/10/2012

    Maybe we should say that we are limited from the faster than light info transfer “so far”.

    Link to this
  9. 9. dadster 4:59 pm 08/10/2012

    Every particle is entangled with every other particle .Entangled state is the basic state of each and every particle in cosmos as all had a single point origin and were together . Communication by electromagnetic waves is but a manifestation of this entangled state. science is just being unraveling its own mysteries step by step according to the development of our measuring instruments and techniques .The best is yet to come !

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  10. 10. JohnKemp 5:21 pm 08/10/2012

    I’m going to use this as an excuse to ask a question that has always puzzled me. Surely this ‘spooky action at a distance’ implies an absolute scale of time, invariant accross space? If it doesn’t, what is meant by ‘instantaneous’ in this context?

    Link to this
  11. 11. bansema 5:43 pm 08/10/2012

    @HowardB, tend to agree (re: tabloidisation ;) ), but then again, this subject is really uncomprehensible when using ‘common sense’ as opposed to the intricate math involved. As far as my humble understanding goes, what is measured is a state change of a member of an entangled pair triggered by the measuring of i.e. the spin or polarization of the member at a distance. Instantaneous is in spacetime (@JohnKemp), the 4-dimensional observable universe, possibly the ‘reflection’ of 16-dimensional reality ;) .

    The paradox of faster than light travel (no teleportation is done here) is solved by the information needed to observe the action at a distance. Think of the remote entangled photon to be locked in a vault. One needs the security code to enter the vault, to get that it needs to be sent by some signal from the location of the other photon (this signal is not going faster than light).

    We don’t know much yet of this beautiful world, but that’s why it is so awesomely interesting :)

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  12. 12. charliefoxtrot 5:57 pm 08/10/2012

    To davefrancis, Quantum Ghost and anybody still holding out for faster-than-light communication:

    Quantum states, even when they’re entangled, are truly random–there is no way, even in theory, to predict their outcomes. Everytime you look at a photon’s polarization, as in the experiment described, you are going to see a random polarization; being entangled means that you know what the polarization of its entangled partner will be without having to actually look at it. But you can’t force a polarization onto a photon; you have to take whatever random polarization you get.

    The entangled photons aren’t really the communication medium, they’re like a cryptographic key that only the sender and recipient can possibly see. You observe the polarization of your photon and that gives you enough information about its partner that you can tell the recipient how to turn their photon into your original photon without having to observe it.

    No information is really passed between the photons. We just know, because they’re entangled, that their polarizations will be correlated, but even in theory there’s no way to force a polarization onto a photon and have it forced on its entangled partner. Therefore there’s no way to communicate using entanglement–all information is transferred via the classical communication medium and the observed polarization, which is totally random, is just used as an encryption key.

    So there may be a way to communicate faster-than-light, or even instantaneously, but if there is it doesn’t work with quantum entanglement, because quantum entanglement really has nothing at all to do with instantaneous communication.

    Link to this
  13. 13. charliefoxtrot 6:16 pm 08/10/2012

    To JohnKemp:

    Which photon gets detected first depends on your frame of reference, according to special relativity. Some inertial frames will see photon A get detected first, and therefore in those frames they’ll know the state of photon B before it is observed.

    In other inertial frames, photon B will get detected first, and they’ll know the state of photon A before it is observed.

    The trick here is that no information is actually passed between the photons via entanglement, so there’s no real causal relationship between the observation of photon A and the change in state of photon B; both frames of reference can state that the observation of their photon caused the collapse of the other photon’s wavefunction without any messy causality problems ensuing.

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  14. 14. charliefoxtrot 6:21 pm 08/10/2012

    (p.s. In case that didn’t make it clear, what I mean is that instantaneous events are only instantaneous in non-relativistic quantum mechanics, which is only an approximation. When you take into account special relativity, what looks instantaneous in one frame of reference is not in another, and no absolute time scale is needed or allowed)

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  15. 15. GreenMind 7:57 pm 08/10/2012

    charliefoxtrot says:

    “Quantum states, even when they’re entangled, are truly random–there is no way, even in theory, to predict their outcomes. Everytime you look at a photon’s polarization, as in the experiment described, you are going to see a random polarization; being entangled means that you know what the polarization of its entangled partner will be without having to actually look at it. But you can’t force a polarization onto a photon; you have to take whatever random polarization you get.”

    What happens if you don’t care what the actual polarization state is, but only care whether Alice has observed her photon?

    The article says: “Because of the link between Alice and Bob forged by entanglement, Bob’s photon instantly feels the effect of the measurement made by Alice. Bob’s photon assumes the quantum state of Alice’s original photon, but in a sort of garbled form. Bob cannot recover the quantum state Alice wanted to teleport until he reverses that garbling by tweaking his photon in a way that depends on the outcome of Alice’s measurement. So he must await word from Alice about how to complete the teleportation—and that word cannot travel faster than the speed of light. That restriction ensures that teleported information obeys the cosmic speed limit.”

    Is the “sort of garbled” state of Bob’s photon something that Bob can observe, like an interference pattern in the old double slit experiments?

    I try to understand entanglement by translating it back into those old experiments, though I am not sure it always can apply. In this case I am imagining that there is a particle emitter that sends a continuous wide stream of particles toward two sets of double slits, one owned by Alice and one owned by Bob. Initially Alice and Bob both observe an interference pattern of particles passing through their pair of slits. If Alice turns on her detector at one slit, she will observe the interference pattern disappear and be replaced by a dot. That leads to a critical question. What happens at Bob’s slit? Does his interference pattern also disappear?

    Without caring what the actual quantum state the particles collapsed into, can Bob tell that Alice turned on her detector by looking for the interference pattern?

    Thanks for any replies.

    Link to this
  16. 16. workingonit 8:34 pm 08/10/2012

    I don’t have much scientific background, but wouldn’t Bob’s attempt to observe an interference pattern cause his photon(s) to stabilize or set (or whatever the terminology is), thereby “interfering” with Alice’s?

    Link to this
  17. 17. Carlos Solrac 11:42 pm 08/10/2012

    It is just ridiculous. We are taking not only faster than light –which may be possible. We are talking instantaneous, infinite velocity. –which is nuts. Infinity is an empty concept, it does not have a place in science –much less in physics.

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  18. 18. Knyaz 2:05 am 08/11/2012

    Возможно телепортация происходит в виде информационно- светового луча.Такой способ передачи информации обнаружен учёными,этот способ использует ген но может он не квантовый а какое то у него другое название.Возможно таким способом происходит переход миров из одного измерения в другое.”Но телепортация не создавать копии как таковой,он просто переносит квантовой информации из одного места в другое,уничтожая оригинал в этом процессе”.Возможно в процессе информационно-светового перехода миров генетически искажённая информация или остаётся в этом измерении или уничтожается совсем(судный день).Может поэтому нашли следы человека рядом со следами динозавров,может динозавры уже существовали в этом измерении а люди перешли из другого.

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  19. 19. gavin reilly 12:58 pm 08/11/2012

    The only thing that can go faster than light is if you change the top spin on an electron in one side of the universe then on the other side of the universe the spin flips on the other side instantly but can not carry any imformation.

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  20. 20. Carlos Solrac 1:56 pm 08/11/2012

    Gavin: the claim of “teleporters” is is not about ‘faster than light’ speed; that would only violates a fundamental law of physics. They are claiming ‘instantaneous speed’ which eviscerates the foundation of logic. Teleporters are doing this as a show of their immense power -the same way Caligula sat his horse in the Roman senate. “They are not even wrong” as Pauli said.

    Link to this
  21. 21. Daniel35 3:01 pm 08/11/2012

    This seems like reading a fairy tale, where we ignore a lot of common sense. Could we non-believers have some meaningful information? How can you do anything with a single photon, except maybe observe it, and necessarily destroy it? What exactly is being teleported? How do you measure qualities of any single particle and produce and detect the signal? Is there anything known or imagined about what the signal consists of? What is meant by “spin up”, down, “polarization” and such of a particle? It sounds like they’re trying to detect something even they don’t understand. It suggests that they look for an electron that matches the expected change.

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  22. 22. workingonit 4:56 pm 08/11/2012

    Seems to me the concepts of speed and movement (i.e. teleportation) do not apply in this situation—and by speaking of the matter in these terms we create confusion. Because certainly, speed seems to be limited by the speed of light. But to the best of my understanding, the photons are linked (sharing a kind of identity, if you will, like two sides of a coin) in a way that is independent of space & distance. Seems to me I’ve heard something similar about the force of gravity, that its effects are independent of time.

    I, too, wonder how the scientists can do anything with a single photon, and then manage to know which other photon is the one it is linked to! But there is so much happening in science these days that I don’t understand, I’m not prepared to claim it’s impossible to do this.

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  23. 23. vinodkumarsehgal 2:38 am 08/12/2012

    Charliefoxtrot (12,13,14)

    Quantum teleportation implies teleportation of quantum state from one place to another. Quantum state of a particle also signifies some information viz spin, polarization, location, mass, charge of a particle. As such, some information is definitely passed out from one place to another. But this transfer of information does not takes place thru any e.m. signal, with speed limited by light speed. On the contrary, this transfer takes place thru weird phenomenon of quantum entanglement in which either information transfer takes place instantly or at superluminal speeds. So the key to understand the quantum teleportation is to understand the mystery of entanglement. In my view, key to understanding of entanglement lies in either in the following :

    i) When both the particles (before entanglement) are in the proximity, all the FUTURE information of one particle is encrypted in the other particle at the stage of entanglement. When the pair of entangled particles are taken apart by any distance, all the future information of one particle remains entangled intact in the other particle.

    ii) Actual information transfer takes place between entangled pair of particles BUT this does not takes place thru e.m signal via 3D space known to Science. This transfer may take place within some higher dimensional space thru some non-e.m energy medium which allows instantaneous transfer or transfer at superluminal speeds.

    Unfortunately, both the above phenomenon are unknown to Science. However, efforts to understand the entanglement within the natural phenomena currently known to Science are inadequate and any forced interpretation does not conforms to a logical and rational approach. So let us admit that with its current knowledge Science does not understand the mystery of teleportation and entanglement.

    Let us wait in future for more mysteries of Nature to unfold before teleportation and entanglement are cracked

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  24. 24. vinodkumarsehgal 2:55 am 08/12/2012

    To Charliefoxtrot (12,13,14)

    Quantum state of a particle are random and these states assume some definite values at the stage of measurement when wave function collapses. Within an entangled pair of particles, will there be some correspondence, some sort of entangled relation, for the random states of both the entangled particles? To paraphrase my query :

    i) Without measurement, will the random states of one entangled particle also reflect on the random state of other entangled particle.

    If we say yes, then will the random states of other entangled particles be truly random in the sense since these states shall be determined by the probability functions of Ist particles. If we say NO, Will they be really entangled?

    ii) At the deterministic measurement stages, of course quantum state of second particle will be determined by the quantum state of first particle BUT what rules will regulate these determination?

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  25. 25. vinodkumarsehgal 3:23 am 08/12/2012

    Article states that “And although part of the transfer happens instantaneously, the steps required to read out the teleported quantum state ensure that no information can be communicated faster than the speed of light”.

    At another stage it states “Bob cannot recover the quantum state Alice wanted to teleport until he reverses that garbling by tweaking his photon in a way that depends on the outcome of Alice’s measurement.”

    Above quotes imply that though measuring the quantum state of one particle determines the quantum state of other particle of entangled pair instantly but this determination is in some “garbled” state. The process to make this “garbled” state “ungarbled”, takes place at subluminal speeds. An information is not an information unless it is ‘ungarbled’ and measured Therefore, despite the fact that teleportation takes place thru entanglement which is instantaneously , practically teleportation takes place at subluminal speeds.

    In view of above, entire process of teleportation reduces to a non-entangled process. So why to bring entanglement in picture?

    Link to this
  26. 26. ryanharford 4:22 am 08/12/2012

    is it research into this area of physic’s specifically over any other area that will break the cosmic barrier , is this the point we must focus on , even if entangled particle’s them selves do not transmit information only that they are in the same state at any particular time , the search to closen the gap of communication from both side’s has to be the hardest task we could do , this can only cause advancement’s in technology , and i can only see physic’s benefiting from this.

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  27. 27. ryanharford 4:26 am 08/12/2012

    Re-hash : entangled particle’s do transmit information instantaneously as does everything at that level

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  28. 28. ryanharford 4:45 am 08/12/2012

    the tech learnt from this of how to speed up un-garbling increasing optic’s for long range information transfer , even if possible prediction algorithm’s for what the state’s will be

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  29. 29. workingonit 12:54 pm 08/12/2012

    Is not all of existence “entangled,” in a sense? Though I find that word misleading, as it implies a multiplicity of essentially separate manifestations. What is it that is manifesting through all we see (and don’t see)? All of existence shares that inner essence. And that inner essence has nothing to do with time and space.

    As an example, many who believe in the power of prayer can intuit that the effects of prayer are immediate, independent of distance.

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  30. 30. Austriak 7:22 pm 08/12/2012

    Well .. we see in the scientific paper and especially the long list of interesting comments, Humanity is still like a blind man groping the dark with regard to this real espect of our natural world. The worldview of the Matrix/DNA Theory makes me uncomfortable because she is suggesting things that nobody else has said anything like that. For example she says that the two photons forming a couple are no more than two representatives-syntheses of the two sides of the formula of the Matrix. Notice the formula: a photon would be the systemic circuit piece that starts at F 1 and goes till F4, and the other would be the piece that goes from F 6 to F 1. So in fact the two photons would be the result of a cut that separated exactly half a pre-existing single photon. The cut of separation is the extra piece of F5. So space and time between photon A and photon B is not empty, it is filled by force of F 5, which can be stretched to infinity, and as the the formula says, is the function responsible for reproduction, both, the entire system into another new system and as the reproduction of the left cheek in his bi-lateral symmetrical and asymmetrical right cheek. But since the formula of the Matrix represents a complete revolution in the life cycle of a body, also means that the life of the pre-existing photon was separated into two halves in two sets, without destroying the link circuit which is the life span. Therefore, two bi-laterally opposite sides and being two phases of life where one is driven by growth and other ruled by degenerative entropy, the two photons are opposite in everything.( more explanations at: http://theuniversalmatrix.com/pt-br/artigos/?p=4635 )

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  31. 31. jtdwyer 7:49 pm 08/12/2012

    These discussions always give me a headache, because there seems to be so much evidence that is subjectively interpreted. I also seem to have difficulty comprehending ‘Bob & Carol & Ted & Alice’ interactions…

    Personally, I cannot quite get past the ‘coincidence’ that pairs of entangled particles are generally produced by splitting a single particle. The simplest explanation of entanglement would be that the relations between particle properties are imparted to their wave forms by the process of splitting – that no communication is necessary at the moment of particle detection to impart any property state information to the as yet undetected particle. In this case their probabilistic state information is established as the particles are initially entangled.

    This conceptual explanation may have been ‘disproven’ by interpretations of experimental evidence, but I’m highly skeptical, until it can be explained what magic otherwise required can produce subsequent ‘instantaneous’ alignment of particle properties.

    Please see:
    http://en.wikipedia.org/wiki/Quantum_entanglement#Methods_of_creating_entanglement
    http://en.wikipedia.org/wiki/Quantum_teleportation

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  32. 32. Quinn the Eskimo 7:53 pm 08/12/2012

    I really want to say something snarky. Like about Star Trek.

    But, I’m reminded that “Watson, come here, I need you” gave no portent to the iPod.

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  33. 33. singing flea 12:32 am 08/13/2012

    I suggest you scientists don’t get your panties in a bunch over this. Taking the massive step from teleportation of a single proton (actually only it’s state of polarization) is a far cry from Scotty beaming up Kirk, Spock and McCoy from a planet in collapse.

    Link to this
  34. 34. Carlos Solrac 4:12 pm 08/13/2012

    Quantum teleportation and quantum computing are an expensive road to nowhere. And my guess is that is going to be a long trip.

    Link to this
  35. 35. iwikler 12:48 pm 08/15/2012

    I thought that any measurement or observation of an entangled particle (or its spin, etc.) by either the sender or receiver breaks the entanglement, thereby rendering the entangled message un-readable, or am I “over-Heisenberging” the issue? Could someone with knowledge in excess of a “Scientific American” education please explain how (and how long) the entanglement remains intact after someone “looks” at it?

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  36. 36. GreenMind 2:58 pm 08/15/2012

    @workingonit

    “I don’t have much scientific background, but wouldn’t Bob’s attempt to observe an interference pattern cause his photon(s) to stabilize or set (or whatever the terminology is), thereby “interfering” with Alice’s?”

    No, both Alice and Bob can observe the interference pattern without causing the mixed eigenstate to collapse. It is when one of them places a detector on one of their slits that the collapse occurs at their own slits, causing the interference pattern to disappear at their own location. But does it disappear at all slits when one of them turns on the detector?

    If Bob’s interference pattern disappears when Alice turns her detector on, then they can use that to communicate. Sure this would violate the laws of physics as we currently understand them, but quantum physics’ “spooky action at a distance” also violated relativity as it was understood then too.

    Has anyone actually done the experiment?

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  37. 37. GreenMind 3:17 pm 08/15/2012

    Carlos Solrac said:
    “It is just ridiculous. We are taking not only faster than light –which may be possible. We are talking instantaneous, infinite velocity. –which is nuts. Infinity is an empty concept, it does not have a place in science –much less in physics.”

    I don’t think the concept is actually concerned with velocity. It is misleading to call the entanglement effect “infinite velocity”. Entanglement is far stranger than just high velocity. Much more mysterious is the idea that particles do not occupy a specific location, and that taking a close look at it causes it to choose a location, momentum, etc., at random. And even more mysterious than that is that this observation causes can cause a particle on the other side of the universe to also choose a location, and that its location, momentum, etc. will be the opposite of the observed particle. The fact that it happens with no physical contact between the particles, and no hidden variables that stores the values, etc., is hard enough to accept, and nobody actually understands how it happens at all. The fact that it happens instantaneously is just one more bit of mystery, and not really the most disturbing.

    We don’t understand time at all, and so an “instantaneous” communication between the particles may just be part of the mystery of time. When we figure out how time works, this may become perfectly obvious.

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  38. 38. Delta5 3:24 pm 08/15/2012

    “Two entangled photons, for instance, can have correlated, opposite polarization states—if one photon is vertically polarized, for instance, the other must be horizontally polarized.”

    Individual photons are not linearly polarized; they are circularly polarized. The two opposite polarization states are right-hand and left-hand circular polarization.

    Link to this
  39. 39. vinodkumarsehgal 4:58 am 08/16/2012

    To GreenMind

    Alice’s Photon will have a random set of all locations and momentum. Bob’s photon which is a entangled with Alice Photon will also exhibit some random set of all locations and momentum. At the time of measurement, both the entangled photons shall be linked thru some relation — H and V spin Or L and R spin etc.. Before measurement, will there be some link – some fixed relation in the random sets of the two entangled photons? In other words, will the quantum values and wave function of Alice Photon have some correspondence with that of Bob Photon?

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  40. 40. GreenMind 4:33 pm 08/16/2012

    vinodkumarsehgal, you ask: “Before measurement, will there be some link – some fixed relation in the random sets of the two entangled photons? In other words, will the quantum values and wave function of Alice Photon have some correspondence with that of Bob Photon?”

    As I understand it, there is no link before measurement. Both particles consist of a cloud of all possible states, and as soon as one is forced to “choose” a set of states, the opposite particle somehow adopts the set of opposite states.

    Link to this
  41. 41. vinodkumarsehgal 5:58 am 08/17/2012

    To Greenmind

    Measurement at one particle is reflective of all the cloud states of that particle. If there is link between the measured states of two entangled particles, why there should be no link between their cloud states? I can not comprehend this

    “and as soon as one is forced to “choose” a set of states, the opposite particle somehow adopts the set of opposite states.”

    Could you please give your considered opinion on this
    “somehow”? I had suspected two streams of mechanism on “somehow” as given in my comment 23 but I am not sure.

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  42. 42. JacobSilver 2:20 pm 08/18/2012

    The American and Chinese physicists are assuring people that the photons at the quantum level are respecting the universal speed of light. But this does not apply at the quantum level, where there is no time. Without time particles can be at two places. It is not entanglement. It is a function of timelessness. Time at the human level, and several levels below, is an emergent quality. The emergence of time actually starts at the atomic level. Below that there is not time. It is not easy for humans to understand events at that level. But it does not help to imagine that the photons have wristwatches.

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  43. 43. vinodkumarsehgal 12:15 am 08/19/2012

    To Jacob Silver

    “The emergence of time actually starts at the atomic level. Below that there is not time”

    Does there space exist below atomic level?

    If below atomic level, time and space do not exist, can energy and matter particles exist without space and time?

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  44. 44. vinodkumarsehgal 6:34 am 08/19/2012

    To Jacob Silver

    Emergent properties emerge out from some higher fundamental entities. If both time and space are emergent properties, what is that fundamental entity which makes their appearance emergent?

    Link to this
  45. 45. GreenMind 6:54 pm 09/11/2012

    vinodkumarsehgal, regarding your two possibilities, the first has apparently been disproven: There is no encryption of information in the two particles. How rigorous this proof is I cannot say, but even if it were true, the fact that observing one particle forces the other to collapse is still a mystery. In fact, how observation causes the first to collapse is a large mystery in itself.

    The second explanation, as you say, involves unknown science.

    There is a third possibility to both collapse and entanglement. Note that research has found that particles are *already* collapsed before the observation takes place, somehow knowing that the observation will take place in its future, and collapsing in anticipation of it. As I see it, when a particle is observed, its quantum collapse extends all the way back to the point at which the two particles separated, and that both of them therefore are in a collapsed state for the entire time they are flying apart. This kind of sounds like time travel, with the collapsed state traveling backwards in time, but I think of it differently. Think of the time line of a particle as a string on a violin, vibrating along its entire length. At any point in time, represented by distance from one end of the string, the string will occupy all the positions that its vibrations allow, a cloud of positions all at the same point in time. Now put your finger on the string in the middle. The string stops vibrating at that point, and also for the entire length of the string on both sides of your finger. It stops vibrating not only “after” the location of the finger, but also “before” (unless someone is playing the violin, thereby keeping one section of the string vibrating.) This would account for the apparent “time travel” of the observation event.

    In entanglement, the strings of two particles are attached at the beginnings of both strings. Stopping one string from vibrating also stops the other. This results in the illusion that both particles stop vibrating (their quantum states collapsing) at the same time, when actually neither of them has been vibrating at all along the lengths of the string. It only looks like something travels instantly from one string to the other, preventing both from vibrating, when actually the collapse has been there all along both timelines, starting at the point the strings separated.

    To restate that, neither string has been vibrating at all because one of them has its vibrations damped by an event (finger) somewhere on its timeline. The cloud of all the positions the particles occupy due to the vibrations of the strings are eliminated by a damping event anywhere on the string.

    This is all just my own idea, based on my limited understanding of what I have read. If it is disproved by any research, I would be grateful to know about it.

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