Quantum contextuality

Summary

Quantum contextuality is the fact that quantum measurement outcomes cannot in general be fixed in advance. More precisely, they cannot be fixed independently of the compatible measurements performed together with them. A measurement context is a set of jointly measurable observables, and a noncontextual model would give each observable one value in all contexts. The Kochen–Specker theorem shows that no such assignment exists in Hilbert spaces of dimension at least $3$. Contextuality is regarded as a resource in some models of quantum computation.