title: Entangling power of passive optical elements.
abstract: We investigate the entangling capability of passive optical elements, both qualitatively and quantitatively. We present a general necessary and sufficient condition for the possibility of creating distillable entanglement in an arbitrary multimode Gaussian state with the help of passive optical elements, thereby establishing a general connection between squeezing and the entanglement that is attainable by nonsqueezing operations. Special attention is devoted to general two-mode Gaussian states, for which we provide the optimal entangling procedure, present an explicit formula for the attainable degree of entanglement, and discuss several practically important special cases.
authors.affiliation: Institute for Mathematical Physics, TU Braunschweig, 38106 Braunschweig, Germany.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Wolf
authors.forename: Jens
authors.initials: J
authors.lastname: Eisert
authors.forename: Martin B
authors.initials: MB
authors.lastname: Plenio