  This article is a short introduction to and review of the cluster-state model
of quantum computation, in which coherent quantum information processing is
accomplished via a sequence of single-qubit measurements applied to a fixed
quantum state known as a cluster state. We also discuss a few novel properties
of the model, including a proof that the cluster state cannot occur as the
exact ground state of any naturally occurring physical system, and a proof that
measurements on any quantum state which is linearly prepared in one dimension
can be efficiently simulated on a classical computer, and thus are not
candidates for use as a substrate for quantum computation.
