Quantitative entanglement witnesses

@article{Eisert2006QuantitativeEW,
  title={Quantitative entanglement witnesses},
  author={Jens Eisert and Fernando G. S. L. Brand{\~a}o and Koenraad M. R. Audenaert},
  journal={New Journal of Physics},
  year={2006},
  volume={9},
  pages={46 - 46}
}
Entanglement witnesses provide tools to detect entanglement in experimental situations without the need of having full tomographic knowledge about the state. If one estimates in an experiment an expectation value smaller than zero, one can directly infer that the state has been entangled, or specifically multi-partite entangled, in the first place. In this paper, we emphasize that all these tests—based on the very same data—give rise to quantitative estimates in terms of entanglement measures… 

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