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Quantum correlations in nanostructured two-impurity Kondo systems

We study the ground-state entanglement properties of nanostructured Kondo systems consisting of a pair of impurity spins coupled to a background of confined electrons. The competition between the RKKY-like coupling and the Kondo effect determines the development of quantum correlations between the different parts of the system. A key element is the electronic filling due to confinement. An even electronic filling leads to results similar to those found previously for extended systems, where the properties of the reduced impurity-spin subsystem are uniquely determined by the spin correlation function defining a one-dimensional phase space. An odd filling, instead, breaks spin-rotation symmetry unfolding a two-dimensional phase space showing rich entanglement characteristics as, e.g., the requirement of a larger amount of entanglement for the development of non-local correlations between impurity spins. We check these results by numerical simulations of elliptic quantum corrals with magnetic impurities at the foci as a case study.