Failure of epistemic models to explain the antidistinguishability of quantum mixed preparations

Understand

We investigate the limits of epistemic models in reproducing the empirical predictions of general quantum preparations.

• This involves comparing the common quantum overlap determined by the anti-distinguishability of a set of preparations with the common epistemic overlap of the probability distribution over the ontic states describing these preparations.
• We show that no epistemic model with non-zero common overlap can reproduce the predictions of quantum theory for mixed preparations, even for qubit systems.
• We explicitly provide sets of distinct mixed preparations, starting from qutrit systems, that give rise to identical quantum mixed states for which the common epistemic overlap must be zero.