Fidelity matters: the birth of entanglement in the interference of Gaussian states

摘要

We address the interaction of two Gaussian states interferring at a beamsplitter and analyze the correlations exhibited by the resulting bipartitesystem. We demonstrate that nonlocal correlations (entanglement) arise if andonly if the fidelity between the two input Gaussian states falls under athreshold value depending only on their purities and on the transmissivity ofthe beam splitter. Our result clarifies the role of squeezing as a prerequisitefor entanglement and provide a tool to optimize the generation of entanglementby passive devices.