Articles & Reviews
Authored by RSF Research Staff
Quantum Communications Satellites Break Entanglement Record
Scientists sent two photon beams from the Micius satellite (named after an ancient Chinese philosopher) down to Delingha, a city in northern China, and Lijiang, a city in southern China. These photon beams had entangled photon pairs when they were transmitted from the satellite. Researchers performed a Bell test to analyze the particles, and confirmed that the photon pairs remained entangled over 1,200 kilometers, breaking the previous record of about 100 kilometers.
"It’s a huge achievement for quantum entanglement and quantum science."
Thomas Jennewein - University of Waterloo, Canada
The technique can be applied to a variety of technological applications, and will help to lead to development of a "quantum Internet," increasing the speed and security of data communications around the world, according to Anton Zeilinger of the University of Vienna.
The experiment solved one of the main problems with quantum communication: when photons travel through air or optical fibers, surrounding molecules in the material or air absorb the photons, limiting their transmission distance. Yet outside the atmosphere, there are fewer "obstacles" for these photons and so the distance they can travel and remain entangled is much further. While this test was performed only between the satellite and locations on the surface of the Earth, we should expect more tests directly between networks of satellites soon.
In order to complete these tests, researchers had to adapt their quantum equipment to work in space, an amazing technological achievement according to physicist Harald Weinfurter of Ludwig-Maximilians-Universität in Munich. Detection was also difficult; beacon lasers were used to pinpoint the satellite location and aim ground-based telescopes in that direction. The accuracy is astonishing: like hitting a single grain of sand from the top of the Eiffel Tower.