Violation of a generalized non-contextuality inequality with single photons
Xiang Zhan, Jian Li, Hao Qin, Zhihao Bian, Yongsheng Zhang, Peng Xue · arXiv (Cornell University) · 2015
Is a violation of Kochen-Specker (KS) non-contextuality inequality a tight bound to rule out the non-contextual hidden variable theory? A test designed by Liang, Spekkens and Wiseman (LSW) provides a more stringent bound and a violation of a generalized non-contextuality inequality such as LSW inequality rules out more generalized non-contextual models including the traditional KS non-contextual models. It is proven that three unsharp binary qubit measurements are enough to violate LSW inequality in a state-dependent manner. We show such measurements can be implemented through joint positive operator-valued measures (POVMs) of noisy spin-1/2 observables and report an experimental realization of the joint POVMs on photonic qubits. We demonstrate an experimental violation of LSW inequality with single photons and provide the experimental evidence of a more stringent bound to rule out the non-contextual models without unwarranted idealizations such as noiseless measurements.unsharp binary qubit measurements.