Navegando por Autor "Taddei, M. M."
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Artigo An introduction to dispersive interactions(IOP Publishing, 2009-11-04) Taddei, M. M.; Mendes, Tarciro Nortarson Chaves; Farina, C.Dispersive forces are a kind of van der Waals intermolecular force which could only be fully understood with the establishment of quantum mechanics and, in particular, of quantum electrodynamics. In this pedagogical paper, we introduce the subject in a more elementary approach, aiming at students with basic knowledge of quantum mechanics. We perform original calculations using a semiclassical method by the name of the fluctuating-dipole method, and focus primarily on the interaction of atoms with macroscopic bodies, in particular with a spherical, less usual geometryArtigo Quantum steering beyond instrumental causal networks(American Physical Society, 2018-04-06) Nery, Ranieri Vieira; Taddei, M. M.; Araújo, Rafael Chaves Souto; Aolita, L.We theoretically predict, and experimentally verify with entangled photons, that outcome communication is not enough for hidden-state models to reproduce quantum steering. Hidden-state models with outcome communication correspond, in turn, to the well-known instrumental processes of causal inference but in the one-sided device-independent scenario of one black-box measurement device and one wellcharacterized quantum apparatus. We introduce one-sided device-independent instrumental inequalities to test against these models, with the appealing feature of detecting entanglement even when communication of the black box’s measurement outcome is allowed.We find that, remarkably, these inequalities can also be violated solely with steering, i.e., without outcome communication. In fact, an efficiently computable formal quantifier—the robustness of noninstrumentality—naturally arises, and we prove that steering alone is enough to maximize it. Our findings imply that quantum theory admits a stronger form of steering than known until now, with fundamental as well as practical potential implicationsArtigo Subtleties in energy calculations in the image method(IOP Publishing, 2009-07-08) Taddei, M. M.; Mendes, Tarciro Nortarson Chaves; Farina, C.In this pedagogical work, we point out a subtle mistake that can be made by undergraduate or graduate students in the computation of the electrostatic energy of a system containing charges and perfect conductors if they naively use the image method. Specifically, we show that naive expressions for the electrostatic energy for these systems obtained directly from the image method are wrong by a factor of 1/2. We start our discussion with well-known examples, namely point charge–perfectly conducting wall and point charge–perfectly conducting sphere, and then proceed to the demonstration of general results, valid for conductors of arbitrary shapes