25-05-2012, 12:37 PM
Teleportation
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Teleportation is the transfer of matter from one point to another, more or less instantaneously, either by paranormal means or through technological means. Teleportation has been widely utilized in works of science fiction.
Similar is apport, an earlier word used to describe what today might be called teleportation; and bilocation, in which an individual or object is said to be, or appears to be, located in two distinct places at the same instant in time. The word "teletransportation" (which simply expands Charles Fort's abbreviated term) was first employed by Derek Parfit as part of a thought exercise on identity.
The word was coined in 1931[1][2] by American writer Charles Fort to describe the strange disappearances and appearances of anomalies, which he suggested may be connected. He joined the Greek prefix tele- (meaning "distant") to the Latin verb portare (meaning "to carry"). Fort's first formal use of the word was in the second chapter of his 1931 book, Lo! "Mostly in this book I shall specialize upon indications that there exists a transportory force that I shall call Teleportation." Though, with his typical half-serious jokiness, Fort added, "I shall be accused of having assembled lies, yarns, hoaxes, and superstitions. To some degree I think so myself. To some degree, I do not. I offer the data."[3] Fort suggested that teleportation might explain various allegedly paranormal phenomena, though, typically, it's sometimes difficult to tell if Fort took his own "theory" seriously, or instead used it to point out what he saw as the
inadequacy of mainstream science to account for strange phenomena.
Scenarios
One proposed means of teleportation is the transmission of data which is used to precisely reconstruct an object or organism at its destination. However, it would be impossible to travel from one point to another instantaneously; faster than light travel, as of today, is believed to be impossible. The use of this form of teleportation as a means of transport for humans still has considerable unresolved technical issues, such as recording the human body with sufficient accuracy to allow reproduction elsewhere (i.e., because of the uncertainty principle), and whether destroying a human in one place and recreating a copy elsewhere would provide a sufficient experience of continuity of existence. The reassembled human might be considered a different sentience with the same memories as the original, as could be easily proved by constructing not just one, but several copies of the original and interrogating each as to the perceived uniqueness of each. Each copy constructed using merely descriptive data, but not matter, transmitted from the origin and new matter already at the destination point would consider itself to be the true continuation of the original and yet this could not logically be true; moreover, because each copy constructed via this data-only method would be made of new matter that already existed at the destination, there would be no way, even in principle, of distinguishing the original from the copies. Many of the relevant questions are shared with the concept of mind transfer.
Dimensional teleportation is another proposed means of teleportation. Often shown in fictional works, particularly in fantasy and comic books, it involves the subject exiting one physical universe or plane of existence, then re-entering it at a different location. This method is rarely seriously considered by the scientific community, as the currently predominant theories about parallel universes assume that physical travel is not possible between them.
A third proposed means of teleportation common in science fiction (and seen in The Culture novels and The Terminator series of films) sends the subject through a wormhole or similar phenomenon, allowing transit faster than light while avoiding the problems posed by the uncertainty principle and potential signal interference. In both of the examples above, this form of teleportation is known as "Displacement" or "Topological shortcut" (Scientific American)[citation needed] which implies that this kind of teleportation may be similar in mechanism to time travel[citation needed]. Displacement teleporters would eliminate many probable objections to teleportation on religious or philosophical grounds, as they preserve the original subject intact — and thus continuity of existence.
Teleportation by means of the mind or innate personal abilities are sometimes referred to as p-Teleportation, "psychoportation", or "jaunting"; named after the fictional scientist (Jaunte) who discovered it in The Stars My Destination (originally titled Tiger! Tiger!), a science fiction novel by Alfred Bester. This method could hypothetically work through any of the mechanisms proposed above, but is usually portrayed in fiction as displacement-type or dimensional teleportation to simplify its use in the story.
Quantum Teleportation
Teleportation is the name given by science fiction writers to the feat of making an object or person disintegrate in one place while a perfect replica appears somewhere else. How this is accomplished is usually not explained in detail, but the general idea seems to be that the original object is scanned in such a way as to extract all the information from it, then this information is transmitted to the receiving location and used to construct the replica, not necessarily from the actual material of the original, but perhaps from atoms of the same kinds, arranged in exactly the same pattern as the original. A teleportation machine would be like a fax machine, except that it would work on 3-dimensional objects as well as documents, it would produce an exact copy rather than an approximate facsimile, and it would destroy the original in the process of scanning it. A few science fiction writers consider teleporters that preserve the original, and the plot gets complicated when the original and teleported versions of the same person meet; but the more common kind of teleporter destroys the original, functioning as a super transportation device, not as a perfect replicator of souls and bodies.
In 1993 an international group of six scientists, including IBM Fellow Charles H. Bennett, confirmed the intuitions of the majority of science fiction writers by showing that perfect teleportation is indeed possible in principle, but only if the original is destroyed. In subsequent years, other scientists have demonstrated teleportation experimentally in a variety of systems, including single photons, coherent light fields, nuclear spins, and trapped ions. Teleportation promises to be quite useful as an information processing primitive, facilitating long range quantum communication (perhaps unltimately leading to a "quantum internet"), and making it much easier to build a working quantum computer. But science fiction fans will be disappointed to learn that no one expects to be able to teleport people or other macroscopic objects in the foreseeable future, for a variety of engineering reasons, even though it would not violate any fundamental law to do so.
In the past, the idea of teleportation was not taken very seriously by scientists, because it was thought to violate the uncertainty principle of quantum mechanics, which forbids any measuring or scanning process from extracting all the information in an atom or other object. According to the uncertainty principle, the more accurately an object is scanned, the more it is disturbed by the scanning process, until one reaches a point where the object's original state has been completely disrupted, still without having extracted enough information to make a perfect replica. This sounds like a solid argument against teleportation: if one cannot extract enough information from an object to make a perfect copy, it would seem that a perfect copy cannot be made. But the six scientists found a way to make an end run around this logic, using a celebrated and paradoxical feature of quantum mechanics known as the Einstein-Podolsky-Rosen effect. In brief, they found a way to scan out part of the information from an object A, which one wishes to teleport, while causing the remaining, unscanned, part of the information to pass, via the Einstein-Podolsky-Rosen effect, into another object C which has never been in contact with A. Later, by applying to C a treatment depending on the scanned-out information, it is possible to maneuver C into exactly the same state as A was in before it was scanned. A itself is no longer in that state, having been thoroughly disrupted by the scanning, so what has been achieved is teleportation, not replication.
As the figure to the left suggests, the unscanned part of the information is conveyed from A to C by an intermediary object B, which interacts first with C and then with A. What? Can it really be correct to say "first with C and then with A"? Surely, in order to convey something from A to C, the delivery vehicle must visit A before C, not the other way around. But there is a subtle, unscannable kind of information that, unlike any material cargo, and even unlike ordinary information, can indeed be delivered in such a backward fashion. This subtle kind of information, also called "Einstein-Podolsky-Rosen (EPR) correlation" or "entanglement", has been at least partly understood since the 1930s when it was discussed in a famous paper by Albert Einstein, Boris Podolsky, and Nathan Rosen. In the 1960s John Bell showed that a pair of entangled particles, which were once in contact but later move too far apart to interact directly, can exhibit individually random behavior that is too strongly correlated to be explained by classical statistics. Experiments on photons and other particles have repeatedly confirmed these correlations, thereby providing strong evidence for the validity of quantum mechanics, which neatly explains them. Another well-known fact about EPR correlations is that they cannot by themselves deliver a meaningful and controllable message. It was thought that their only usefulness was in proving the validity of quantum mechanics. But now it is known that, through the phenomenon of quantum teleportation, they can deliver exactly that part of the information in an object which is too delicate to be scanned out and delivered by conventional methods.
This figure compares conventional facsimile transmission with quantum teleportation (see above). In conventional facsimile transmission the original is scanned, extracting partial information about it, but remains more or less intact after the scanning process. The scanned information is sent to the receiving station, where it is imprinted on some raw material (eg paper) to produce an approximate copy of the original. By contrast, in quantum teleportation, two objects B and C are first brought into contact and then separated. Object B is taken to the sending station, while object C is taken to the receiving station. At the sending station object B is scanned together with the original object A which one wishes to teleport, yielding some information and totally disrupting the state of A and B. The scanned information is sent to the receiving station, where it is used to select one of several treatments to be applied to object C, thereby putting C into an exact replica of the former state of A.