Entanglement witnesses and a loophole problem
Quantum Physics
2007-07-18 v2
Abstract
We consider a possible detector-efficiency loophole in experiments that detect entanglement via the local measurement of witness operators. Here, only local properties of the detectors are known. We derive a general threshold for the detector efficiencies which guarantees that a negative expectation value of a witness is due to entanglement, rather than to erroneous detectors. This threshold depends on the local decomposition of the witness and its measured expectation value. For two-qubit witnesses we find the local operator decomposition that is optimal with respect to closing the loophole.
Keywords
Cite
@article{arxiv.quant-ph/0608058,
title = {Entanglement witnesses and a loophole problem},
author = {Patrick Skwara and Hermann Kampermann and Matthias Kleinmann and Dagmar Bruss},
journal= {arXiv preprint arXiv:quant-ph/0608058},
year = {2007}
}
Comments
5 pages, 2 figures, published version