Gaussian intrinsic entanglement for states with partial minimum uncertainty

Abstract

We develop a theory of a quantifier of bipartite Gaussian entanglement called Gaussian intrinsic entanglement (GIE) which was proposed recently in [L. Mi\v{s}ta {\it et al.}, Phys. Rev. Lett. {\bf 117}, 240505 (2016)]. The GIE provides a compromise between computable and physically meaningful entanglement quantifiers and so far it was calculated for two-mode Gaussian states including all symmetric partial minimum-uncertainty states, weakly mixed asymmetric squeezed thermal states with partial minimum uncertainty, and weakly mixed symmetric squeezed thermal states. We improve the method of derivation of GIE and we show, that all previously derived formulas for GIE of weakly mixed states in fact hold for states with higher mixedness. In addition, we derive analytical formulas for GIE for several new classes of two-mode Gaussian states with partial minimum uncertainty. Finally, it is shown, that like for all previously known states, also for all new states the GIE is equal to Gaussian R\'{e}nyi-2 entanglement of formation. This finding strengthens a conjecture about equivalence of GIE and Gaussian R\'{e}nyi-2 entanglement of formation for all bipartite Gaussian states.