The experimental setup and techniques are simple, elegant, and quite well controlled. The research group had little room for error, since the discrepancy between the classical bound (or inequality) imposed by the Yu-Oh formulation of SIC and the value predicted by quantum mechanics is tiny (only aboutOf course, if you read further, it doesn't rule out all of the classical noncontextuality due to the nagging problem with many photon systems - the detection loophole. Still, if you go by the body of evidence, the QM scenario has shown perfect agreement with experiments so far.
4%). Despite unavoidable experimental uncertainties, the measurements by Zu et al. violated the classical bound (thus ruling out noncontextuality) by about 5standard deviations, irrespective of the prepared system’s state. This statistically significant result sets a very good benchmark for experimental SIC with a single quantum system.
 C. Zu, Y-X. et al., Phys. Rev. Lett. 109, 150401 (2012).