  We describe a generalization of the cluster-state model of quantum
computation to continuous-variable systems, along with a proposal for an
optical implementation using squeezed-light sources, linear optics, and
homodyne detection. For universal quantum computation, a nonlinear element is
required. This can be satisfied by adding to the toolbox any single-mode
non-Gaussian measurement, while the initial cluster state itself remains
Gaussian. Homodyne detection alone suffices to perform an arbitrary multi-mode
Gaussian transformation via the cluster state. We also propose an experiment to
demonstrate cluster-based error reduction when implementing Gaussian
operations.
