Quantum contextuality in a Young-type interference experiment

We show that correlations between the detector positions at the two-photon Young interference plane exhibit contextual behavior. Contextuality is demonstrated by showing the violation of the n-cycle noncontextuality inequalities [M. Araujo et al., Phys. Rev. A 88, 022118 (2013)] for any even number n of observables ranging from 4 to 14. These violations exclude noncontextual hidden-variable theories as an explanation of the conditional two-photon Young pattern. Unlike recent contextuality experiments, ours is free of the compatibility loophole.