Increasing entanglement between Gaussian states by coherent photon subtraction
Résumé
We experimentally demonstrate that the entanglement between Gaussian entangled states can be increased by non-Gaussian operations. Coherent subtraction of single photons from Gaussian quadrature-entangled light pulses, created by a non-degenerate parametric amplifier, produces delocalized ”Schroedinger kitten” states with complex negative Wigner functions, more entangled than the initial states in terms of negativity. The experimental results are in very good agreement with the theoretical predictions.