The dream of teleportation is to be able to travel by simply reappearing at some distant location. It might appear that one could scan the object and send the information so that the object can be reconstructed at the destination. In conventional facsimile transmission an original object is scanned to extract partial information about it. The scanned information is sent to the receiving station, where it is used to produce an approximate copy of the original object. The original remains intact after the scanning process. By contrast, in quantum teleportation, the uncertainty principle forbids any scanning process from extracting all the information in a quantum state. Charles H. Bennett and his coworkers showed that a quantum state can be teleported provides one does not know that state using a celebrated and paradoxical feature of quantum mechanics known as the Einstein- Podolsky-Rosen (EPR) 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, part of the information to pass, via the EPR effect. Two objects B and C form an entangled pair, object C is taken to the sending station, while object B is taken to the receiving station. At the sending station object C is scanned together with the original object A, yielding some information and totally disrupting the state of A and C. The scanned information is sent to the receiving station, where it is used to select one of several treatments to be applied to object B, thereby putting B into an exact replica of the former state of A.
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