Objectivity, basis ambiguity, and the classical simulability of concordant quantum computation
The paper investigates quantum computations that have zero discord, meaning they lack entanglement and other correlations but are hard to simulate classically without knowing a specific local basis. It argues this difficulty stems from 'basis ambiguity'—the lack of a uniquely identifiable local product basis—which is linked to the absence of 'basis objectivity,' a redundant record of the local basis. This ambiguity provides a quantum advantage in cryptography.