Entanglement swapping as event-ready entanglement preparation

In this contribution the preparation of event-ready entanglement in polaris ed photons by means of entanglement swapping is studied. This protocol make s use of Gaussian photon-sources. Since the states resulting from this prot ocol are equivalent to those obtained by mixing two photons in a 50:50 beam splitter, the nature of the emerging entanglement is controversial. Severa l methods to enhance the fidelity of the outgoing state are studied. It is found that at least quantum non-demolition measurements or a quantum comput er of some kind is needed to create event-ready entanglement with entanglem ent swapping.