Navegando por Autor "Milani, Giorgio"
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Artigo Device-independent test of a delayed choice experiment(American Physical Society, 2019-08-12) Polino, Emanuele; Agresti, Iris; Poderini, Davide; Carvacho, Gonzalo; Milani, Giorgio; Lemos, Gabriela Barreto; Araújo, Rafael Chaves Souto; Sciarrino, FabioThe wave or particle duality has long been considered a fundamental signature of the nonclassical behavior of quantum phenomena, especially in a delayed choice experiment, where the experimental setup revealing either the particle or the wave nature of the system is decided after the system has entered the apparatus. However, as counterintuitive as it might seem, usual delayed choice experiments do have a simple causal explanation. Here, we take a different route and under a natural assumption about the dimensionality of the system under examination, we present an experimental proof of the nonclassicality of a delayed choice experiment based on the violation of a dimension witness inequality. Our conclusion is reached in a device-independent and detection loophole-free manner, that is, based solely on the observed data and without the need of special assumptions about the measurement apparatusArtigo Experimental nonclassicality in a causal network without assuming freedom of choice(Nature Communications, 2023-02-17) Polino, Emanuele; Poderini, Davide; Rodari, Giovanni; Agresti, Iris; Suprano, Alessia; Carvacho, Gonzalo; Wolfe, Elie; Canabarro, Askery; Moreno Filho, Marcos George Magalhães; Milani, Giorgio; Spekkens, Robert W.; Araújo, Rafael Chaves Souto; Sciarrino, FabioIn a Bell experiment, it is natural to seek a causal account of correlations wherein only a common cause acts on the outcomes. For this causal structure, Bell inequality violations can be explained only if causal dependencies are modeled as intrinsically quantum. There also exists a vast landscape of causal structures beyond Bell that can witness nonclassicality, in some cases without even requiring free external inputs. Here, we undertake a photonic experiment realizing one such example: the triangle causal network, consisting of three measurement stations pairwise connected by common causes and no external inputs. To demonstrate the nonclassicality of the data, we adapt and improve three known techniques: (i) a machine-learning-based heuristic test, (ii) a data-seeded inflation technique generating polynomial Bell-type inequalities and (iii) entropic inequalities. The demonstrated experimental and data analysis tools are broadly applicable paving the way for future networks of growing complexityArtigo Experimental test of quantum causal influences(Sciance Advances, 2022-02-25) Agresti, Iris; Poderini, Davide; Polacchi, Beatrice; Miklin, Nikolai; Gachechiladze, Mariami; Suprano, Alessia; Polino, Emanuele; Milani, Giorgio; Carvacho, Gonzalo; Araújo, Rafael Chaves Souto; Sciarrino, FabioSince Bell’s theorem, it is known that local realism fails to explain quantum phenomena. Bell inequality violations manifestly show the incompatibility of quantum theory with classical notions of cause and effect. As recently found, however, the instrumental scenario—a pivotal tool in causal inference—allows for nonclassicality signatures going beyond this paradigm. If we are not limited to observational data and can intervene in our setup, then we can witness quantum violations of classical bounds on the causal influence among the involved variables even when no Bell-like violation is possible. That is, through interventions, the quantum behavior of a system that would seem classical can be demonstrated. Using a photonic setup—faithfully implementing the instrumental causal structure and switching between observation and intervention run by run—we experimentally witness such a nonclassicality. We also test quantum bounds for the causal influence, showing that they provide a reliable tool for quantum causal modelingArtigo Experimental violation of n-locality in a star quantum network(Nature Research, 2020-05-18) Poderini, Davide; Agresti, Iris; Marchese, Guglielmo; Polino, Emanuele; Giordani, Taira; Suprano, Alessia; Valeri, Mauro; Milani, Giorgio; Spagnolo, Nicolò; Carvacho, Gonzalo; Araújo, Rafael Chaves Souto; Sciarrino, FábioThe launch of a satellite capable of distributing entanglement through long distances and the first loophole-free violation of Bell inequalities are milestones indicating a clear path for the establishment of quantum networks. However, nonlocality in networks with independent entanglement sources has only been experimentally verified in simple tripartite networks, via the violation of bilocality inequalities. Here, by using a scalable photonic platform, we implement star-shaped quantum networks consisting of up to five distant nodes and four independent entanglement sources. We exploit this platform to violate the chained n-locality inequality and thus witness, in a device-independent way, the emergence of nonlocal correlations among the nodes of the implemented networks. These results open new perspectives for quantum information processing applications in the relevant regime where the observed correlations are compatible with standard local hidden variable models but are nonclassical if the independence of the sources is taken into account