Stoklasa, B.Motka, L.Řeháček, J.Hradil, Z.Sánchez Soto, Luis LorenzoAgarwal, Girish S.2023-06-182023-06-182015-111367-263010.1088/1367-2630/17/11/113046https://hdl.handle.net/20.500.14352/24324©2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. We acknowledge illuminating discussions with Gerd Leuchs, Elisabeth Giacobino, and Andrea Aiello. This work was supported by the Grant Agency of the Czech Republic (Grant 15-031945), the European Social Fund and the State Budget of the Czech Republic POSTUP II (Grant CZ.1.07/2.3.00/30.0041), the IGA of Palacky University (Grant PrF-2015-002), and the UCM-BSCH Program (Grant GR3/14).Optical beams with topological singularities have a Schmidt decomposition. Hence, they display features typically associated with bipartite quantum systems; in particular, these classical beams can exhibit entanglement. This classical entanglement can be quantified by a Bell inequality formulated in terms of Wigner functions. We experimentally demonstrate the violation of this inequality for Laguerre-Gauss (LG) beams and confirm that the violation increases with increasing orbital angular momentum. Our experimental scheme, which is designed to give directly the parity of the Wigner function, yields negativity at the origin for LG_10 beams, whereas for LG_20 we always get a positive value.engAtribución 3.0 Españahttps://creativecommons.org/licenses/by/3.0/es/journal articlehttp://dx.doi.org/10.1088/1367-2630/17/11/113046http://iopscience.iop.org/open access535Orbital angular-momentumQuantum entanglementWigner functionNonlocalityCoherenceStatesRadiometryEntropyFieldsSpaceÓptica (Física)2209.19 Óptica Física