Gabriel Ignacio Senno (ICFO), Matteo Lostaglio (ICFO)
If one chooses noncontextuality as one’s notion of classicality, then it is known that no-cloning cannot be regarded as a non-classical phenomenon. There are, in fact, several noncontextual ontological models which reproduce large subsets of quantum theory and contain a no-cloning theorem. In this work, however, we show that the phenomenology of cloning is indeed nonclassical but not for the reasons usually adduced. Specifically, we focus on the task of state-dependent cloning and prove that the optimal cloning fidelity predicted by quantum theory cannot be explained by any noncontextual model. We derive a noise-robust noncontextuality inequality whose violation by quantum theory not only implies a quantum advantage for the task of state-dependent cloning but also provides an experimental witness of noncontextuality.