Quantum nonlocality without entanglement

@article{Bennett1999QuantumNW,
  title={Quantum nonlocality without entanglement},
  author={Charles H. Bennett and David P. DiVincenzo and Christopher A. Fuchs and Tal Mor and Eric M. Rains and Peter W. Shor and John A. Smolin and William K. Wootters Ibm and Cal Tech and Universit́e de Montŕeal and Att and Williams},
  journal={Physical Review A},
  year={1999},
  volume={59},
  pages={1070-1091}
}
We exhibit an orthogonal set of product states of two three-state particles that nevertheless cannot be reliably distinguished by a pair of separated observers ignorant of which of the states has been presented to them, even if the observers are allowed any sequence of local operations and classical communication between the separate observers. It is proved that there is a finite gap between the mutual information obtainable by a joint measurement on these states and a measurement in which only… 

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