Entangled discord: when quantum correlations precede quantum systems

G. BELLOMO

Workshop; International Workshop: Identity, indistinguishability and non-locality in quantum physics; 2017

From a physical viewpoint, classical and quantum systems are defined ?and treated? in many different manners. Regarding its states? spaces, while classical systems are generally described by its coordinates (or statistical distributions) in the corresponding phase space, standard quantum theory focuses on state operators over the relevant Hilbert spaces. In Asher Peres (maybe pessimistic) words: ?[in quantum mechanics] we must be content with a vague ?definition?: A quantum system is whatever admits a closed dynamical description within quantum theory.? In this sense, there seems to be some ambiguity in the way to define what a quantum system is and, in turn, to uncover the quantum correlations between its subsystems. This situation has been already intensively studied from the perspective of entanglement-like correlations. In this talk, I will review the problem from an information-theoretic and algebraic point of view, bringing up the issue of general quantum correlations ?as discord-type ones? and the relation between its quantification and the mentioned ambiguity. Furthermore, I will show several cases in which different decompositions of the same physical system enhances the accessible quantum resources and provides a more flexible definition of quantumness measures.