Teleportation

The term teleportation, widely used in science fiction literature, may be broadly defined as the [Page 1226]act of transferring an object from one location to another without the actual movement of the object through the space separating the two locations. This implies, therefore, that not only is the space required for travel eliminated from the process, but also the time of travel is eliminated, or nearly so. Several theories have been put forward to explain how such movement of persons or inanimate objects would take place. These include movement by psychic means, or through manipulation of the spacetime vacuum or geometry, or even through parallel universes. At present, the reality of teleportation is somewhat different from the definition given above, which arose partly out of decades of science fiction lore. This entry explains why this is so, followed by an outline of the general steps currently being employed in teleportation schemes in the scientific world, along with some of the actual experiments performed in the past decade and a half.

The steps required to facilitate the teleportation of an object may be generalized as follows: The exact composition of the original object is identified, after which the object at that location is disassembled. The details of the object's makeup are then transmitted to the final location and an exact copy of the original object is constructed. Despite what has been portrayed in current and past works of science fiction, teleportation of macroscopic objects is not yet part of the foreseeable future. Teleporting a human, for example, would first involve analyzing approximately 1028 atoms that are found within the human body. Storing the information obtained would require vast amounts of space. At present (and even in the foreseeable future), there is no computer technology available to handle that capacity of data, while even with the best possible technology, accessing and transmitting this information would take millions of centuries. In 1982, another problem arose from Dennis Dieks, William Kent Wootters, and Wojciech H. Zurek's no-cloning theorem, which, as its name implies, states that it is impossible to make an exact copy of any quantum particle. The major reason, however, for the impracticability of macroscopic teleportation is the violation of one of the key principles of quantum physics, Heisenberg's uncertainty principle. This principle states that it is impossible to know simultaneously all the properties of a quantum particle. The problem that arises is that in replicating the original object, all the information about each particle in the object must be known. The uncertainty principle makes this impossible.

While teleportation of macroscopic objects is not yet a reality in the scientific world, in 1993 a team of six international scientists (Charles Bennett, Gilles Brassard, Claude Crépeau, Richard Jozsa, Asher Peres, and William Wootters) proposed a mechanism for another type of teleportation (quantum teleportation) that obeyed all the laws of physics. Quantum teleportation may be defined as the transfer of quantum information from one particle to another some distance away; the state of a system, and not the system itself, is transferred. It uses a feature of quantum mechanics known as entanglement, along with the transmission of classical information, to transfer an unknown quantum state to some arbitrary location. Entanglement, also known as the Einstein-Podolsky-Rosen effect, is a property exhibited by quantum systems that are correlated with each other in some way, even though they may be separated spatially. States that are entangled are often regarded as one quantum system because of the strong correlations that exist between them. Entanglement is essential to any teleportation protocol, because it allows the state being transferred to remain unknown; there is, therefore, no violation of the Heisenberg uncertainty principle.

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