Entangling Power of Passive Optical Elements
Michael M. Wolf, Jens Eisert, Martin Bodo Plenio · Physical Review Letters · 2003
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.