  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.
