  We employ a trapped ion to study quantum contextual correlations in a single
qutrit using the 5-observable KCBS inequality, which is arguably the most
fundamental non-contextuality inequality for testing Quantum Mechanics (QM). We
quantify the effect of systematics in our experiment by purposely scanning the
degree of signaling between measurements, which allows us to place realistic
bounds on the non-classicality of the observed correlations. Our results
violate the classical bound for this experiment by up to 25 standard
deviations, while being in agreement with the QM limit. In order to test the
prediction of QM that the contextual fraction increases with the number of
observables, we gradually increase the complexity of our measurements from 5 up
to 121 observables. We find stronger-than-classical correlations in all
prepared scenarios up to 101 observables, beyond which experimental
imperfections blur the quantum-classical divide.
