We implemented a triply entangled Greenberger-Horne-Zeilinger(GHZ)-like state and coherently manipulated the spin, path, and energy degrees of freedom in a single neutron system. The GHZ-like state was analyzed with an inequality derived by Mermin: we determined the four expectation values and finally obtained M = 2.558 +/- 0.004 > 2, which exhibits a clear violation of the noncontextual assumption and confirms quantum contextuality.
@article{arxiv.0908.0623,
title = {Engineering of triply entangled states in a single-neutron system},
author = {Yuji Hasegawa and Rudolf Loidl and Gerald Badurek and Stephan Sponar and Helmut Rauch},
journal= {arXiv preprint arXiv:0908.0623},
year = {2015}
}