Quantum Teleportation Accross the River Danube

Quantum teleportation of individual qubits has thus far been limited to laboratory distances. We intend to extend these techniques to larger distances by exploiting the possibility of using glass fiber optics in a channel underneath the river Danube in Vienna. There we have the stations of Alice and Bob and above the river there will be a direct connection for the classical channel. A most interesting feature of that experiment will exploit the fact that the speed of light in glass fibers is only 2/3 of the speed in free space. Therefore, using very fast electronics, it can be expected that the classical signal propagating in free space can actually be transmitted from Alice's station at a time after the photon has been launched but still arrive at Bob's station significantly early enough to set unitary transformation at Bob's side in time such that the arriving photon will be subject to the appropriate unitary transformation, in order to become an exact replica of the original.

Rupert Ursin, Thomas Jennewein, Markus Aspelmeyer, Rainer Kaltenbaek, Michael Lindenthal, Anton Zeilinger

Quantum teleportation link across the Danube
Nature 430, 849 (2004)