Generating superposition of up-to three photons for continuous variable   quantum information processing
  We develop an experimental scheme based on a continuous-wave (cw) laser for generating arbitrary superpositions of photon number states. In this experiment, we successfully generate superposition states of zero to three photons, namely advanced versions of superpositions of two and three coherent states. They are fully compatible with developed quantum teleportation and measurement-based quantum operations with cw lasers. Due to achieved high detection efficiency, we observe, without any loss correction, multiple areas of negativity of Wigner function, which confirm strongly nonclassical nature of the generated states. 
Mitsuyoshi Yukawa, Kazunori Miyata, Takahiro Mizuta, Hidehiro   Yonezawa, Petr Marek, Radim Filip, Akira Furusawa
quant-ph