In everyday life it is only natural that the properties of objects exist independent of being observed or not. The quantum world on the other hand is ruled by other laws: the property of a particle may be defined not until the instant it is being measured, and two entangled particles seem to be connected in a non-local way over large distances.
Various experiments worldwide have proven this fundament of quantum theory. However, up to now last doubts could not be ruled out completely. Advocates of “local realism,” by which the classical world is governed, refer to several “loopholes” which have been identified in order to save their world view. Now, physicists from the group of Prof. Anton Zeilinger at the Institute of Quantum Optics and Quantum Information (IQOQI) in Vienna, Austria, have closed an important loophole in photonic experiments which use quantum entanglement to rule out a local