Brussels, 25 Feb 2003
Six years ago, when physicists successfully teleported photons for the first time, the world wondered what would be next. Could people or large objects be teleported? Would quantum communication become a reality?
Working out of the University of Innsbruck in Austria in 1997, Jian-Wei Pan was part of a team of physicists using quantum teleportation processes to take a photon, or any other quantum-scale particle, and transfer its properties to another photon. But there was a catch. To do this, they had to destroy the photons to ensure successful teleportation. Reporting in Nature this month, Pan and colleagues at the University of Vienna have gone one step further, teleporting photons without having to destroy them first. They think their breakthrough could be the first step towards long-distance quantum communication.
Not everyone agrees. Observers of the 1997 experiment felt that quantum teleportation would never allow for faster-than-light communication. "Although the teleported particle attains the polarization [sic] value instantly, the people at the sending station must convey the fact that teleportation was successful by making a phone call or using some other light speed or sub-light-speed means of communication," according to the American Institute of Physics. So, what has changed to make it possible now?
Living next door to Alice
In quantum teleportation, the sender – oddly named 'Alice' – instantly transfers the quantum state of the particle to a receiver, called 'Bob'. Until recently, complications in this experiment, causing what Physicsweb calls "spurious events", meant that certain detectors destroyed the photon in the registration process. The Vienna team used filters to reduce the intensity of the photons being transported, significantly reducing these spurious events and increasing the teleportation accuracy to 97%.
With such precision, according to Physicsweb, "the teleported protons could be used in 'quantum repeaters' for long-distance communication". Used in combination with what Pan's team call "entanglement purification", quantum communication could yet become a reality. But for science fiction buffs hoping to be beamed up, the American Institute of Physics offers this reality check.
"[Schemes like this] are intended only for quantum-scale particles, such as photons and atoms. Although no existing laws of physics prevent quantum teleportation from being carried out in humans and automobiles, it is extremely unlikely that this scheme could be carried out in such macroscopic objects..."
Depiction of the experimental set-up for achieving quantum teleportation in 1997.
Contact: research@cec.eu.int
More information on this subject:
Physicsweb's 'Teleportation moves on'
American Institute of Physics comments on teleportation
DG Research
http://europa.eu.int/comm/dgs/research/i ndex_en.html