How to test the “quantumness” of a quantum computer?

@article{Zagoskin2014HowTT,
  title={How to test the “quantumness” of a quantum computer?},
  author={Alexandre M. Zagoskin and E. Il'ichev and M. Grajcar and Joseph J. Betouras and Franco Nori},
  journal={Frontiers in Physics},
  year={2014},
  volume={2},
  pages={33}
}
Recent devices, using hundreds of superconducting quantum bits, claim to perform quantum computing. However, it is not an easy task to determine and quantify the degree of quantum coherence and control used by these devices. Namely, it is a difficult task to know with certainty whether or not a given device (e.g., the D-Wave One or D-Wave Two) is a quantum computer. Such a verification of quantum computing would be more accessible if we already had some kind of working quantum computer, to be… 
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