The Danube River is known for its beauty and has been immortalized in song. Now researchers have employed the water body as a testing ground for quantum teleportation. Scientists report today in the journal Nature that they have successfully teleported photons more than 600 meters across the famous waterway.
Rupert Ursin and his colleagues at the Institute for Experimental Physics in Vienna fired a laser through a barium borate crystal to generate two pairs of photons. One pair is entangled, which means that if something disturbs the state of one, the other feels the effects as well--even when they are not physically connected. By separating the entangled pair, the scientists successfully transported information about the state of one photon to the other. Using fiber-optic cable laid under the water in sewer pipes, together with microwaves sent across the air above the water, three distinct states were teleported across the Danube. Over the course of a 28-hour experimental run, the system was correct 97 percent of the time.
The results indicate that quantum teleportation is feasible over long distances and under real-world conditions, the scientists say. "Our result," they write, "is a step towards the implementation of a quantum repeater, which will enable pure entanglement to be shared between distant parties in a public environment and eventually on worldwide scale."