  An entanglement-generating protocol is described for two qubits coupled to a
cavity field in the bad-cavity limit. By measuring the amplitude of a field
transmitted through the cavity, an entangled spin-singlet state can be
established probabilistically. Both fundamental limitations and practical
measurement schemes are discussed, and the influence of dissipative processes
and inhomogeneities in the qubits are analyzed. The measurement-based protocol
provides criteria for selecting states with an infidelity scaling linearly with
the qubit-decoherence rate.
