1,721,081 research outputs found
Insights into Quantum Contextuality and Bell Nonclassicality: A Study on Random Pure Two-Qubit Systems
Full text linkWe explore the relationship between Kochen-Specker quantum contextuality and
Bell-nonclassicality for ensembles of two-qubit pure states. We present a
comparative analysis showing that the violation of a noncontextuality
inequality on a given quantum state reverberates on the Bell-nonclassicality of
the considered state. In particular, we use suitable inequalities that are
experimentally testable to detect quantum contextuality and nonlocality for
systems in a Hilbert space of dimension . While contextuality can be
assessed on different degrees of freedom of the same particle, the violation of
local realism requires parties spatially separated.Comment: Submitted to Int. J. Theor. Phys. as part of the Collection IQSA22 -
Quantum Structures for Interdisciplinary Application
Advantages of quantum communication revealed by the reexamination of hyperbit theory limitations
Full text linkPaw{\l}owski and Winter's hyperbit theory, proposed in 2012, presented itself
as an alternative to quantum theory, suggesting novel ways of redefining
entanglement and classical communication paradigms. This research undertakes a
meticulous reevaluation of hyperbit theory, uncovering significant operational
constraints that question its equivalence with quantum mechanics. Crucially,
the supposition that hyperbit theory and quantum theory are equivalent relies
on the receiver having unattainable additional knowledge about the sender's
laboratory, indicating that the work by Pawlowski and Winter is incorrect. This
study accentuates the constraints of hyperbits in information processing and
sheds light on the superiority of quantum communication, thereby advancing the
investigation at the intersection of classical and quantum communication
Family of multipartite separability criteria based on a correlation tensor
No full textA family of separability criteria based on correlation matrix (tensor) is provided. Interestingly, it unifies several criteria known before like, e.g., computable cross-norm or realignment criterion (CNNR), de Vicente criterion, and derived recently separability criterion based on symmetric informationally complete positive operator valued measures (SIC POVMs). It should be stressed that, unlike the well-known correlation matrix criterion or criterion based on local uncertainty relations, our criteria are linear in the density operator and hence one may find unexplored classes of entanglement witnesses and positive maps. Interestingly, there is a natural generalization to multipartite scenario using multipartite correlation matrix. We illustrate the detection power of the above criteria on several well-known examples of quantum states
Enhanced realignment criterion vs linear entanglement witnesses
No full textIt is shown that the enhanced (nonlinear) realignment criterion is equivalent to the family of linear criteria based on correlation tensor. These criteria generalize the original (linear) realignment criterium and give rise to the family of entanglement witnesses. An appropriate limiting procedure is proposed which leads to a novel class of witnesses which are as powerful as the enhanced realignment criterion
On the Fidelity Robustness of CHSH–Bell Inequality via Filtered Random States
Full text linkThe theorem developed by John Bell constituted the starting point of a revolution that translated a philosophical question about the nature of reality into the broad and intense field of research of the quantum information technologies. We focus on a system of two qubits prepared in a random, mixed state, and we study the typical behavior of their nonlocality via the CHSH–Bell inequality. Afterward, motivated by the necessity of accounting for inefficiency in the state preparation, we address to what extent states close enough to one with a high degree of nonclassicality can violate local realism with a previously chosen experimental setup
Optimality of generalized Choi maps in
No full textA family of linear positive maps in the algebra of complex matrices proposed recently in Bera et al. arXiv:2212.03807 is further analyzed. It provides a generalization of a seminal Choi nondecomposable extremal map in . We investigate when generalized Choi maps are optimal, i.e. cannot be represented as a sum of positive and completely positive maps. This property is weaker than extremality, however, it turns out that it plays a key role in detecting quantum entanglement
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