SCIENCE - Detection of single photons via quantum entanglement

Almost 200 years ago, Bavarian physicist Joseph von Fraunhofer discovered dark lines in the sun's spectrum. It was later discovered that these spectral lines can be used to infer the chemical composition and temperature of the sun's atmosphere. Today we are able to gain information about diverse objects ...

http://phys.org/news/2013-07-photons-quantum-entanglement.htm