  We performed an experimental test of the Kochen-Specker theorem based on an
inequality derived from the Peres-Mermin proof, using spin-path (momentum)
entanglement in a single neutron system. Following the strategy proposed by
Cabello et al. [Phys. Rev. Lett. 100, 130404 (2008)], a Bell-like state was
generated and three expectation values were determined. The observed violation
2.291 +/- 0.008 > 1 clearly shows that quantum mechanical predictions cannot be
reproduced by noncontextual hidden variables theories.
