Resilience of multiphoton entanglement under losses
Gabriel A. Durkin, Christoph Simon, Jens Eisert, Dirk Bouwmeester · Physical Review A · 2004
We analyze the resilience under photon loss of the bipartite entanglement present in multiphoton states produced by parametric down-conversion. The quantification of the entanglement is made possible by a symmetry of the states that persists even under polarization-independent losses. We examine the approach of the states to the set of positive partial transpose states as losses increase, and calculate the relative entropy of entanglement. We find that some bipartite distillable entanglement persists for arbitrarily high losses.