Abstract

One notion of non-locality in quantum theory is the fact that information may be encoded in a composite system in such a way that it is not accessible through local measurements, even with the assistance of classical communication. Thus, contrary to the classical case, there exists information in quantum many body systems which cannot be accessed locally. Perhaps surprisingly, this sense of non-locality is distinct to a more famous manifestation of quantum non-locality, namely entanglement: there exist sets of states with no entanglement, which contain information that cannot be accessed locally, and vice-versa. In addition to theoretical interest, measurement non-locality is of practical relevance, as local measurements are readily performed in the lab in a range of physical systems. In this talk I will introduce measurement non-locality and show that, remarkably, if information is confined to any two-dimensional subspace of a multi-partite system, all physically allowed measurements can be performed locally: there is no truly non-local information in a single encoded qubit.