First Experimental Quantum Teleportation

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. Yet, fundamental laws like the Heisenberg uncertainty relation do not allow one to measure any object to arbitrary precision. Charles H. Bennett and his co-workers have suggested that it is possible to transfer even quantum states, provided one does not get any information about the state. This becomes possible by utilizing entanglement, one of the essential features of quantum mechanics.

Here we present the first experimental verification of quantum teleportation. producing pairs of entangled photons by the process of parametric down-conversion and using two-photon interferometry for analysing the entanglement, we could transfer a quantum property (in our case the polarization state) from one photon to another.

A pulse of UV-light passing through a nonlinear crystal creates the ancillary entangled pair of photons 2 and 3. After retroflection during its second passage through the crystal the UV-pulse creates another pair of photons. One of these will be the teleported photon 1. It can be prepared to have any polarization. Photon 4, deteced by detector p, serves as a trigger to indicate that photon 1 is under way.

ALICE then looks for coincidences behind a beam splitter BS2 where photon 1 and the anciliaries are superposed. BOB, after receiving the clasical information that ALICE obtained a coincidence count in detectors f1 and f2 identifying the Bell state , knows that his photon 3 is in the initial state of photon 1. This he can check using polarization analysis with the polarizing beam splitter PBS and the detectors d1 and d2.

Thus, photon 3 will turn out to have exactly the properties of photon 1 as defined by the polarizer.

Dik Bouwmeester, Jian-Wei Pan, Klaus Mattle, Manfred Eibl, Harald Weinfurter & Anton Zeilinger

Experimental Quantum Teleportation
Nature 390 (1997) 575-579