Device-independent certification of entangled measurements.

@article{Rabelo2011DeviceindependentCO,
  title={Device-independent certification of entangled measurements.},
  author={Rafael Rabelo and Melvyn Ho and Daniel Cavalcanti and Nicolas Brunner and Valerio Scarani},
  journal={Physical review letters},
  year={2011},
  volume={107 5},
  pages={050502}
}
We present a device-independent protocol to test if a given black-box measurement device is entangled, that is, has entangled eigenstates. Our scheme involves three parties and is inspired by entanglement swapping; the test uses the Clauser-Horne-Shimony-Holt Bell inequality, checked between each pair of parties. In the case where all particles are qubits, we characterize quantitatively the deviation of the measurement device from a perfect Bell-state measurement.