Authors: Xiao-Song Ma; Johannes Kofler; Angie Qarry; Nuray Tetik; Thomas Scheidl; Rupert Ursin; Sven Ramelow; Thomas Herbst; Lothar Ratschbacher; Alessandro Fedrizzi; Thomas Jennewein; Anton Zeilinger Journal: Proc Natl Acad Sci U S A Date: 2013-01-03 Impact factor: 11.205