title: State-independent quantum contextuality with single photons.
abstract: We present an experimental state-independent violation of an inequality for noncontextual theories on single particles. We show that 20 different single-photon states violate an inequality which involves correlations between results of sequential compatible measurements by at least 419 standard deviations. Our results show that, for any physical system, even for a single system, and independent of its state, there is a universal set of tests whose results do not admit a noncontextual interpretation. This sheds new light on the role of quantum mechanics in quantum information processing.
authors.affiliation: Department of Physics, Stockholm University, S-10691, Stockholm, Sweden.
authors.forename: Elias
authors.initials: E
authors.lastname: Amselem
authors.forename: Magnus
authors.initials: M
authors.lastname: Rådmark
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bourennane
authors.forename: Adán
authors.initials: A
authors.lastname: Cabello