Experimental observation of four-photon entanglement from parametric down-conversion.
We observe polarization entanglement between four photons produced from a single down-conversion source. The nonclassical correlations between the measurement results violate a generalized Bell inequality for four qubits. The characteristic properties and its easy generation with high interferometric contrast make the observed four-photon state well suited for implementing advanced quantum communication schemes such as multiparty quantum key distribution, secret sharing, and telecloning.
Eibl
Manfred
M
Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
Gaertner
Sascha
S
Bourennane
Mohamed
M
Kurtsiefer
Christian
C
Zukowski
Marek
M
Weinfurter
Harald
H