Quantum nonlocality obtained from local states by entanglement purification.
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.
Walther
P
P
Institut für Experimentalphysik, Universität Wien, Boltzmanngasse 5, 1090 Vienna, Austria.
Resch
K J
KJ
Brukner
C
C
Steinberg
A M
AM
Pan
J-W
JW
Zeilinger
A
A