  We study the dynamics of a pair of molecular ensembles trapped inside a
superconducting resonator through which they are strongly coupled via a
microwave field mode. We find that entanglement can be generated via "vacuum
fluctuations" even when the molecules and cavity field are initially prepared
in their ground state. This entanglement is created in a relatively short time
and without the need for further manipulation of the system. It does,
therefore, provide a convenient scheme to entangle two mesoscopic systems, and
may well be useful quantum information processing.
