We present the experimental detection of genuine multipartite entanglement using entanglement witness operators. To this aim we introduce a canonical way of constructing and decomposing witness operators so that they can be directly implemented with present technology. We apply this method to three- and four-qubit entangled states of polarized photons, giving experimental evidence that the considered states contain true multipartite entanglement.
@article{arxiv.quant-ph/0309043,
title = {Witnessing multipartite entanglement},
author = {Mohamed Bourennane and Manfred Eibl and Christian Kurtsiefer and Sascha Gaertner and Harald Weinfurter and Otfried Guehne and Philipp Hyllus and Dagmar Bruss and Maciej Lewenstein and Anna Sanpera},
journal= {arXiv preprint arXiv:quant-ph/0309043},
year = {2009}
}