Quantum non-Gaussianity of frequency up-converted single photons
  Nonclassical states of light are an important resource in today's quantum communication and metrology protocols. Quantum up-conversion of nonclassical states is a promising approach to overcome frequency differences between disparate subsystems within a quantum information network. Here, we present the generation of heralded narrowband single photons at 1550 nm via cavity enhanced spontaneous parametric downconversion (SPDC) and their subsequent up-conversion to 532 nm. Quantum non-Gaussianity (QNG), which is an important feature for applications in quantum information science, was experimentally certified for the first time in frequency up-converted states. 
Christoph Baune, Axel Sch\"onbeck, Aiko Samblowski, Jarom\'ir   Fiur\'a\v{s}ek and Roman Schnabel
quant-ph