Quantum realism: axiomatization and quantification

The emergence of an objective reality in line with the laws of the microscopic world has been the focus of longstanding debates. Recent approaches seem to have reached a consensus at least with respect to one aspect, namely, that the encoding of information about a given observable in a physical degree of freedom is a necessary condition for such observable to become an element of the physical reality. Taking this as a fundamental premise and inspired by quantum information theory, here we build an axiomatization for quantum realism -- a notion of realism compatible with quantum theory. Our strategy consists of listing some physically-motivated principles able to characterize quantum realism in a ``metric'' independent manner. We introduce some criteria defining monotones and measures of realism and then search for potential candidates within some celebrated information theories -- those induced by the von Neumann, R\'enyi, and Tsallis entropies. We explicitly construct some classes of entropic quantifiers that are shown to satisfy (almost all of) the proposed axioms and hence can be taken as faithful estimates for the degree of reality (or definiteness) of a given physical observable. Hopefully, our framework may offer a formal ground for further discussions on foundational aspects of quantum mechanics.Comment: 15 pages, 4 figure

High-dimensional monitoring and the emergence of realism via multiple observers

Quantum measurements are unitary evolutions followed by partial traces. Based on that, we address the problem of the emergence of physical reality from the quantum world by introducing a model that interpolates between weak and strong non-selective measurements for qudits. Our model, which is based on generalized observables and Heisenberg-Weyl operators, suggests that for high-dimensional qudits, full information about the system can only be obtained by making the system interact with not just one but several environmental qudits, following a Quantum Darwinism framework.Comment: 12 pages, 2 figure