  We propose a deterministic implementation of weak cubic nonlinearity, which
is a basic building block of a full scale CV quantum computation. Our proposal
relies on preparation of a specific ancillary state and transferring its
nonlinear properties onto the desired target by means of deterministic Gaussian
operations and feed-forward. We show that, despite the imperfections arising
from the deterministic nature of the operation, the weak quantum nonlinearity
can be implemented and verified with the current level of technology.
