A. Delgado, I.H. Deutsch and T. Tessier
PROC. SPIE INT. SOC. OPT. ENG. 5105 (2003)
Individual members of an ensemble of identical systems coupled toa common probe can become entangled with one another, even when they do not interact directly. We investigate how this type of multipartite entanglement is generated in the context of a system consisting of an ensemble of N two-level atoms resonantly coupled to a single mode of the electromagnetic field. In the case where N=2, the dynamical evolution is studied in terms of the entanglements in the different bipartite divisions of the system, as quantified by the I-tangle. We also propose a generalization of the so-called residual tangle that quantifies the inherent three-body correlations in this tripartite system. This allows us to give a complete characterization of the phenomenon of entanglement sharing in the case of the two-atom Tavis-Cummings model. We also introduce an entanglement monotone which constitutes a lower bound on the I-tangle of an arbitrary bipartite system. This measure is seen to be useful in quantifying the entanglement in various bipartite partitions of the TCM in the case where N > 2, i.e., when there is no known analytic form for the I-tangle.