Experimentally Testable State-Independent Quantum Contextuality

We show that there are Bell-type inequalities for noncontextual theories that are violated by any quantum state. One of these inequalities between the correlations of compatible measurements is particularly suitable for testing this state-independent violation in an experiment.

Figure 1

Each dot represents a unit vector $v_{ij}$. Each of the 6 sides of the regular hexagon and each of the 3 rectangles contains only orthogonal vectors. Note that, for clarity’s sake, most labels have no unit length.