title: Quantum nonlocality obtained from local states by entanglement purification.
abstract: We have applied an entanglement purification protocol to produce a single entangled pair of photons capable of violating a Clauser-Horne-Shimony-Holt Bell inequality from two pairs that individually could not. The initial poorly entangled photons were created by a controllable decoherence that introduced complex errors. All of the states were reconstructed using quantum state tomography which allowed for a quantitative description of the improvement of the state after purification.
authors.affiliation: Institut für Experimentalphysik, Universität Wien, Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Walther
authors.forename: K J
authors.initials: KJ
authors.lastname: Resch
authors.forename: C
authors.initials: C
authors.lastname: Brukner
authors.forename: A M
authors.initials: AM
authors.lastname: Steinberg
authors.forename: J-W
authors.initials: JW
authors.lastname: Pan
authors.forename: A
authors.initials: A
authors.lastname: Zeilinger