Contextuality without access to a tomographically complete set

Understand

The non-classicality of single quantum systems can be formalised using the notion of contextuality.

• But can contextuality be convincingly demonstrated in an experiment, without reference to the quantum formalism? The operational approach to contextuality due to Spekkens requires finding operationally equivalent preparation procedures.
• Previously these have been obtained by demanding indistinguishability under a set of measurements taken to be tomographically complete.
• In the language of generalised probability theories, this requires the ability to explore all the dimensions of the system's state space.