  We describe a measurement-based state preparation scheme for the efficient
build up of cluster states in atom-cavity systems. As in a recent proposal for
the generation of maximally entangled atom pairs [Metz et al., Phys. Rev. Lett.
97, 040503 (2006)], we use an electron shelving technique to avoid the
necessity for the detection of single photons. Instead, the successful fusion
of smaller into larger clusters is heralded by an easy-to-detect macroscopic
fluorescence signal. High fidelities are achieved even in the vicinity of the
bad cavity limit and are essentially independent of the concrete size of the
system parameters.
