In 1935 Schr\"odinger introduced the terms entanglement and steering in the context of the famous gedanken experiment discussed by Einstein, Podolsky, and Rosen (EPR). Here, we report on a sixfold increase of the observed EPR-steering effect as quantified by the Reid-criterion. We achieved an unprecedented low conditional variance product of about 0.04 < 1, where 1 is the upper bound below which steering is present. The steering effect was observed on an unconditional two-mode-squeezed entangled state that contained a total vacuum state contribution of less than 8%, including detection imperfections. Together with the achieved high interference contrast between the entangled state and a bright coherent laser field, our state is compatible with efficient applications in high-power laser interferometers and fiber-based networks for entanglement distribution.
@article{arxiv.1112.0461,
title = {Strong Einstein-Podolsky-Rosen steering with unconditional entangled states},
author = {Sebastian Steinlechner and Jöran Bauchrowitz and Tobias Eberle and Roman Schnabel},
journal= {arXiv preprint arXiv:1112.0461},
year = {2013}
}