  Quantum contextuality is a nonintuitive property of quantum mechanics, that
distinguishes it from any classical theory. A complementary quantum property is
quantum nonlocality, which is an essential resource for many quantum
information tasks. Here we experimentally study the contextual and nonlocal
properties of polarization biphotons. First, we investigate the ability of the
biphotons to exhibit contextuality by testing the violation of the KCBS
inequality. In order to do so, we used the original protocol suggested in the
KCBS paper, and adjusted it to the real scenario, where some of the biphotons
are distinguishable. Second, we transmitted the biphotons through different
unital channels with controlled amount of noise. We measured the decohered
output states, and demonstrated that the ability to exhibit quantum
contextuality using the KCBS inequality is more fragile to noise than the
ability to exhibit nonlocality.

Quantum Physics