We present a general method to quantify both bipartite and multipartite entanglement in a device-independent manner, meaning that we put a lower bound on the amount of entanglement present in a system based on observed data only but independently of any quantum description of the employed devices. Some of the bounds we obtain, such as for the Clauser-Horne-Shimony-Holt Bell inequality or the Svetlichny inequality, are shown to be tight. Besides, device-independent entanglement quantification can serve as a basis for numerous tasks. We show in particular that our method provides a rigorous way to construct dimension witnesses, gives new insights into the question whether bound entangled states can violate a Bell inequality, and can be used to construct device independent entanglement witnesses involving an arbitrary number of parties.
@article{arxiv.1302.1336,
title = {Device-independent entanglement quantification and related applications},
author = {Tobias Moroder and Jean-Daniel Bancal and Yeong-Cherng Liang and Martin Hofmann and Otfried Gühne},
journal= {arXiv preprint arXiv:1302.1336},
year = {2013}
}