Entanglement witnesses and detection of nonlocal superpositions
A. J. Gutiérrez-Esparza, Wanderson M. Pimenta, Breno Marques, A. A. Matoso, J. L. Lucio M., Jan Sperling, W. Vogel, Sebastião Pádua · Latin America Optics and Photonics Conference · 2014
A complete characterization of entanglement in a two-qutrit state generated using the transverse spatial correlations of two parametric down-converted photons is discussed. We verify entanglement for a particular case via entanglement witness operators which are decomposed into a sum of local observables. Experimentally, these operators are accomplished by using a spatial light modulator and a polarizing beam splitter. The quantification of entanglement is computed by the negativity. We also realize an experiment for the verification of the Schmidt number of quantum correlated photons. This measure of entanglement counts the number of global superpositions of product states which are needed to describe a compound quantum system. For unraveling a certain value of this measure, a family of entanglement and Schmidt number tests is constructed.