Preparation contextuality powers parity-oblivious multiplexing

Understand

In a noncontextual hidden variable model of quantum theory, hidden variables determine the outcomes of every measurement in a manner that is independent of how the measurement is implemented.

• Using a generalization of this notion to arbitrary operational theories and to preparation procedures, we demonstrate that a particular two-party information-processing task, "parity-oblivious multiplexing," is powered by contextuality in the sense that there is a limit to how well any theory described by a noncontextual hidden variable model can perform.
• This bound constitutes a "noncontextuality inequality" that is violated by quantum theory.
• We report an experimental violation of this inequality in good agreement with the quantum predictions.