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Does the Heisenberg Uncertainty Principle make human teleportation impossible?

  1. Feb 25, 2010 #1
    Scientists have reportedly been able to transport atoms and molecules as much as 1800 feet. Could the same be done for humans, or would the Heisenberg Uncertainty Principle ultimately make it impossible?
     
  2. jcsd
  3. Feb 25, 2010 #2
    Technically, the Physicists involved in the research you indicated did not "teleport atoms" ex-number of feet. Rather, the physicists were proving the GHZ hypothesis, which is a hypothesis to violate Bell's Inequalities. In other words, the experiment demonstrated a phonomena called entanglement. There was no sending of atoms "from here to there using a teleportation device".

    The uncertainty principle states that the quantity of one non-commuting observable becomes less known when the quantity of the other observable becomes more known. Thus, the HUP has nothing to do with 'teleportation'. Note that the HUP applies to quantum systems, only.
     
  4. Feb 26, 2010 #3
    Well would the HUP make a device like, say, a transporter from Star Trek impossible?
     
  5. Feb 26, 2010 #4
    I would agree with Glen that teleportation processes have absolutely nothing to do with the uncertainty principle.

    However, I do not agree that the "teleportation processes" were simply just experiments proving the GHZ hypothesis. There was indeed teleportation of some form (the meaning of this teleportation as that defined by Charles Bennett in his seminal paper). This teleportation obviously does not defy any physical laws; it involves the teleportation of a quantum state (information) across space. Recently, Hotta proposed and studied a scheme for the teleportation of energy as well.

    It may help if I briefly describe Bennett's standard teleportation protocol. Using the standard communication terminologies, we have two characters Alice and Bob. Now, Alice has a particle prepared in a certain state unknown to her, and she wishes to communicate that information to Bob, giving him a replica of that particle state. Trivially Alice can give the particle to Bob directly, but there may be reasons against that. (for instance, if the quantum channel that I am about to describe has already been set up, it is far easier to "teleport" the state)

    To establish the quantum channel, Alice prepares another two particles in an EPR singlet state (ie the two particles are entangled), and sends one of the particles to Bob. She then performs a joint measurement on the initial particle and her channel particle, entangling the three particles. The measurement will cause the system to collapse into one of several possible states, and destroy the entanglement. Based on her results, Alice has to communicate classically with Bob such that he can perform the appropriate recovery operations (Pauli rotations) in order to turn the state of his particle into the original one Alice had. As such, the particle is not physically teleported across space; it is the information, the state of the particle that is teleported to another particle.

    Refer to: C. H. Bennett, G. Brassard, C. Crépeau, R. Jozsa, A. Peres, W. K. Wootters, Teleporting an Unknown Quantum State via Dual Classical and Einstein-Podolsky-Rosen Channels, Phys. Rev. Lett. 70, 1895-1899 (1993) for more information.


    Now, in the quantum realm, particles are indistinguishable. We cannot for instance, tell two free electrons apart. So, in order to "teleport" humans, we need humans to be decomposed into indistinguishable entities loaded with "states" that make us who we are. Then, we will have a quantum channel comprising two such entities and your state is teleported from your originally occupied entity to the one at the destination. Even ignoring decoherence and the fact that you are a classical object, this sounds rather ludicrous to me.
     
  6. Feb 26, 2010 #5
    So, long story short, are "Star Trek" style transporters are physically unlikely? Physically impossible?
     
  7. Feb 26, 2010 #6

    ZapperZ

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    How about this answer: It hasn't been shown convincingly yet (as in experimentally) to be possible.

    Will that answer get you to actually spend time trying to understand what is meant by "quantum teleportation"?

    Zz.
     
  8. Feb 26, 2010 #7
    I actually somewhat understand what quantum teleportation is. I'm more curious as to how physical teleportation (again, a la Star Trek) can be achieved. So is it, at least in theory, possible? Could there be something we don't know about the laws of physics that could allow Scotty to beam us up?
     
  9. Feb 26, 2010 #8

    ZapperZ

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    Then I'm confused. You originally asked about the HUP and teleportation. I'm assuming that you are asking about quantum teleportation. Now, it appears not to be the case.

    In "The Emperor's New Mind", Penrose had already detailed one possible explanation on why such a device may not work. The inability to completely capture all the possible states of a system (due to QM) and then "replaying" it back to the identical state would make such a phenomenon not work, or at least, you won't get back what you originally captured. The act of sampling the original system will already cause it to be in a particular state (from a superposition of states to a particular state). So all you can "replay" is what you measured, not what the system was before you measure.

    Zz.
     
  10. Feb 26, 2010 #9
    "Quantum Teleportation" has been experimentally verified for qubit states of photons and atoms. See the following references.

    Experimental quantum teleportation
    D Bouwmeester; J W Pan; K Mattle; M Eibl; H Weinfurter; A Zeilinger
    Nature; Dec 11, 1997; vol. 390, pages 575-579

    Deterministic quantum teleportation with atoms
    M Riebe; H Haffner; C F Roos; W Hansel; et al.
    Nature; Jun 17, 2004; vol. 429, pages 734-737

    Deterministic quantum teleportation of atomic qubits
    M D Barrett; J Chiaverini; T Schaetz; J Britton; et al.
    Nature; Jun 17, 2004; vol. 429, pages 737-739

    Penrose's book was published in 1989, before Bennett et al. published their paper proposing quantum teleportation in 1993. Before Bennett et al., physicists were unaware of the possibility of "teleporting" a quantum state with "perfect" fidelity. So it turns out that it is theoretically possible to teleport a human, and so far experimenters have actually been able to teleport qubit states of photons and atoms. However, it would be immensely difficult to actually teleport a human, because first we would need to (as described by Fightfish above) create two human-sized blobs of matter that are entangled, and physically transport (the old fashioned way) one of the blobs of matter to the place that we want to teleport the human, all the while maintaining the entanglement of the two blobs of matter. As Fightfish mentioned, humans are essentially classical objects, which indicates that it would be extremely difficult to entangle two human sized objects, and extremely difficult to maintain that entanglement during the physical transport process. The blobs of matter would interact with the environment in such a way that the purity of their quantum state would be destroyed (decoherence) and they would become essentially classical objects again. Without the pair of entangled human-size objects, one at the departure location and one at the destination location, it would be impossible to teleport a human.

    Note that teleportation does not allow you to travel faster than the speed of light. Before your teleportation is complete, Alice has to send the results of her measurement to Bob, via a classical communication channel (radio waves or whatever). Once Bob receives the results, he can perform some operations on his entangled blob to recover the human. Also, this teleportation presupposes that one of the entangled blobs has already been physically transported to Bob's location, so, if you factor this into the travel time, then the maximum teleportation speed is half the speed of light. Also note that the teleportation process destroys the original "copy" of the human. This means that you don't really exist anywhere for the time during which the classical message is being sent from Alice to Bob.

    Finally, if we suppose that we could overcome the technical difficulties of teleporting a human, we are still left with the following question: If I teleport my body from Earth to Mars, does my mind follow it? Science still has a very poor understanding of the relationship between the mind and body. Some philosophers would say that mind is a different type of substance from body. It's not clear if my mind, with all my memories and my sense of identity, will be intact after teleporting my brain to Mars. Am I still the same person I was before I was teleported?
     
    Last edited: Feb 26, 2010
  11. Feb 26, 2010 #10

    ZapperZ

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    You need to read a bit more carefully. The references you quoted, and all the so-called "teleportation" experiments are demonstration of quantum entanglement of the STATES. It isn't a teleportation of the object itself!

    When you entangled 2 photons, you entangled, say, the SPIN STATES. You sent one photon one way, and the other photon the other way. The photons are already at the various locations when you make such a measurement on one, thus causing the other to have the corresponding spin state. The proper spin state is the one that gets transferred, NOT the physical object, the way one is expecting from a Star Trek "teleportation"!

    Zz.
     
  12. Feb 26, 2010 #11
    I'm fully aware that it is just teleportation of the "quantum state", not the object itself. That's why I said that teleportation has been verified for "qubit states" of photons and atoms. I debated about adding that clarification to an already long post. However, given that sub-atomic particles of the same type are indistinguishable (i.e. one electron is just like any other electron--the only differences between electrons are the quantum states that they are in), all that matters is that the quantum state is teleported from one particle to the other. Once the state of electron A has been teleported to electron B, electron B looks and behaves exactly like electron A, so it is just as good as having the original electron A at the new location. As has been said before, you are teleporting information about the quantum state of the original object. In effect, Bob creates a copy of the original object, though the copying process destroys the original.

    ...Also, I'm aware that it was not the entire state vector for the photons that was teleported, only the portion of the state vector describing the spin state (or in some experiments it was the polarization state). So far, only two-dimensional vector states have been teleported, but it is theoretically possible to teleport state vectors of higher dimension.
     
  13. Feb 26, 2010 #12

    ZapperZ

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    So then, what are you disputing with my posting by citing all this? Isn't this rather highly irrelevant in light of what the OP is now asking for? Did you think ANY of the papers you cited actually showed the teleportation of an object from one location to another? It is the entangled observable that is involved here, not the object!

    Zz.
     
  14. Feb 26, 2010 #13
    We both agree that the object itself is not teleported, it is the quantum state that is teleported. The point is that, for all intents and purposes, a particle at point B in the state [itex]\psi[/itex] is identical to a particle at point A in the state [itex]\psi[/itex]. Furthermore, after the teleportation, the particle at point A is no longer in the state [itex]\psi[/itex]--it has collapsed into one of the eigenstates because it was measured by Alice. If I teleport my computer from Los Angeles to New York, clearly it is not constructed out of the exact same electrons, protons, and neutrons that it was made out of in L.A., but it is still made out of the same number of electrons, protons, and neutrons that are collectively in the same quantum state that my computer was in before it was teleported. So my computer will still have all the same data and programs on it, and it will still run just as well as it did in L.A. There will be absolutely no observable difference between the teleported computer and the original computer. In my view, this means I have succeeded in teleporting my computer. The particular atoms and molecules making up a human are continuously being replaced through the biological processes of cell death, growth, and regeneration--the question of which particular particles in the universe make up a human is metaphysics. What is physically important is the configuration of those particles--the quantum state. So the answer to the original poster's question is yes, you can in theory teleport a human.
     
  15. Feb 27, 2010 #14
    So would teleportation of a human using the method you described involve disintegrating, and therefore killing, the human who's being teleported?
     
  16. Feb 27, 2010 #15
    Also, in his book 'The Physics of Star Trek', Lawrence Krauss says:

    "The operation of quantum teleportation requires very carefully prepared initial quantum states and then a system that is isolated from its environment throughout the process. Nothing could be further from the situation we exist in, however. We are not quantum objects. If we were, the laws of quantum mechanics would not seem so strange. Macroscopic objects like humans are complex configurations of many particles interacting so frequently with each other and their environment that all quantum mechanical correlations and entanglements are quickly destroyed."

    What exactly does this mean? Is it true?
     
  17. Feb 27, 2010 #16

    Chronos

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    The 'Star Trek" process seems unnecessarily complicated. If you can 'read' all the information necessary for teleportation, you can copy it. In which case, Captain Kirk and his crew never left the transporter room, they merely 'beamed' down dopplegangers. The transorter also serves as a superb weapons delivery system. Why fire a photon torpedo when you can transport it to the bridge of an enemy ship once the 'shields' are down?
     
  18. Feb 27, 2010 #17

    Chronos

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    Seriously though, how would you 'capture' and 'transport' the quantum pattern of a life form? You would need to instantaneously record all the quantum states of the reluctant volunteer to accurately recreate it at a distance. The 'reconstitution' process would also need to be instantaneous to avoid decoherence.
     
  19. Feb 27, 2010 #18

    rcgldr

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    The movie "Prestige", got the right idea behind "transporters". You make a copy, then optionally destroy the original.
     
  20. Feb 27, 2010 #19
    Teleporting a human seems near impossible. However, would it be made any easier with advances in technology (singularity, AI, quantum computing, etc.) and energy (fusion)?

    Also, regarding the decoherence of the blobs of matter, is this what Krauss was talking about in his book?
     
    Last edited: Feb 27, 2010
  21. Feb 27, 2010 #20

    ZapperZ

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    The problem here is that you made a copy of WHAT?

    Let's start with the simplest example. You want to make a copy of an atom. After all, if you can't copy an atom, what hope is there to copy whole objects? So now what do you do? You get some huge computer who can make a "scan" of the state of the atom at a particular time. So what are you scanning? You scan the energy state, momentum, location, etc. of the atom. This includes know where the electrons are in that atom. But wait, if you do that, then the momentum of those electrons can have a huge possible range, depending on how well you know the position. Not only that, you've removed ALL of the superposition of these observables, which was the situation the atom was in before you scanned it.

    So what you have is a large set of information of the condition of the atom upon measurement. When you reconstruct that atom, do you think you are getting the ORIGINAL atom back?

    Zz.
     
  22. Feb 27, 2010 #21

    rcgldr

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    No I don't think you get the original back, just an approximate copy. An analogy would be using some type of laser scanning device on a simple, single material object, sending the data to a manufacturing site, that would then use a computerized cutter tool to make an approximate copy.
     
  23. Feb 27, 2010 #22
    Yes, this teleportation method would destroy the original version of the human. Though, when I say destroy, I don't mean that the human just disappears. The particles making up the human will still be there, but they will be in a state that probably won't look too much like an alive human.

    Advances in quantum computing could help the field of quantum teleportation, and vice versa, because quantum computing and quantum teleportation are very closely related fields.

    Yeah, the decoherence of the blobs of matter is the same thing that Krauss was talking about in The Physics of Star Trek. The original quantum teleportation proposal by Bennett et al. was a simple process involving an isolated quantum system. If the system is perfectly isolated, we don't need to worry about unwanted interactions between the particles in the system and particles in the surrounding environment. But in the real world there are always unwanted interactions that create "quantum noise" or "decoherence". In other words, the interaction of the system with the environment can mess up the entangled quantum states that are needed to perform the teleportation. This problem becomes more and more difficult to deal with as the system becomes more macroscopic.
     
  24. Feb 27, 2010 #23

    vanesch

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    Yes. Well. It is an interesting philosophical question :smile:

    Indeed, if you want to "copy" an exact quantum state, you have to modify the original (read: destroy it). Of course, that's under the assumption that in order to have a human being "the same", you need to have it exact up to the quantum state. It might be that human beings are much more sloppy devices, which only need more or less the right atoms at more or less the right places, so that one could do with an inaccurate position measurement of each atom in a human being, write that information on a classical information carrier (say a huge hard disk), and then transmit this information in a classical way to a remote "reconstruction unit" which places each atom more or less at the indicated positions, making a more or less comparable twin to the original, with (?) more or less the same ideas. In this case, the original is not necessarily destroyed, remained in place, and all we did was to fabricate a kind of twin with more or less similar memories on a remote place in a reconstruction unit. The original will not have any sensation of voyage.

    But it might be that a human being is only really a human being "on the quantum level", and then there is no way but to destroy the original to (potentially) reconstruct that quantum state somewhere else (there's a theorem about that in quantum mechanics the name of which I've forgotten which states that it is not possible to "copy" a quantum state without destroying the original).

    And then the question is indeed: is this a murder of a human being, followed by a synthesis of a clone ? Or is this a kind of "transportation" ?

    Imagine you take a quantum transportation to Alpha Centauri. How does that go ? First of all, you need a reconstruction machine on Alpha centauri, and a quantum channel. If all that is in place, you can now get blown up by a bright laser flash that vaporises your body entirely on earth, and a lot of detectors that capture "the measurement". This information is then transmitted through, say, a laser beam, to Alpha centauri. 4 years later, that beam arrives there, and if the machine works well there, they have stocks of carbon, hydrogen, oxygen and other atoms ready to reconstruct your body, and put it in the exact quantum state it was when you were vaporised. Is this reconstructed body "you" ? And did it hurt being vaporized ? And where were you during these 4 years ? And if the beam got dispersed by some interstellar dust, you might be reconstructed slightly differently. Would you go for it ? :uhh:

    EDIT: I was talking from memory about the no-cloning theorem (I removed the wiki link as the article is really not very clear).
     
    Last edited: Feb 27, 2010
  25. Feb 28, 2010 #24
    So you're saying that the interactions between particles in the system and between the system and the environment cause decoherence. So would this decoherence essentially render the teleportation impossible? Can it be overcome by, say, putting a human in a suit and then putting him in a vacuum?

    Can all of these limitations be overcome, however, with sufficiently advanced technology? Michio Kaku says it's possible within a century, I believe. Couldn't, say, a type II civilization do it?
     
  26. Feb 28, 2010 #25
    Yes, the decoherence/quantum noise does make the teleportation of a human extremely difficult. I'm guessing that putting a human in a vacuum does reduce the quantum noise to some degree, but that measure alone would probably not be nearly enough. One thing to keep in mind regarding vacuum is that even the best laboratory vacuums (pressures of around 10-12 torr) still have a particle density of around 35,000 particles per cubic centimeter. So a human in an ultrahigh vacuum still has plenty of interaction with the environment.

    In the field of quantum computation there is an area called quantum error-correction, which is a set of procedures used to mitigate the effects of quantum noise on quantum information. I don't know much about quantum error-correction, but perhaps it provides some hope that a few centuries from now we will have the capability of teleporting macroscopic objects. Though I don't think quantum error-correction makes it any easier to create entanglement between two macroscopic objects (as needed by the quantum teleportation procedure). Personally I'm doubtful that we'll ever be able to teleport a macroscopic object, but a few hundred years from now, who knows? Also, I wouldn't actually want to teleport myself, given all the philosophical problems mentioned above by vanesch.
     
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