  Unitary non-Gaussian nonlinearity is one of the key components required for
quantum computation and other developing applications of quantum information
processing. Sufficient operation of this kind is still not available, but it
can be approximatively implemented with help of a specifically engineered
resource state constructed from individual photons. We present experimental
realization and thorough analysis of such quantum resource state, and confirm
that the state does indeed possess properties of a state produced by unitary
dynamics driven by cubic nonlinearity.
