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To date, most efforts to demonstrate quantum nonlocality have concentrated on systems of two (or very few) particles. It is however difficult in many experiments to address individual particles, making it hard to highlight the presence of…

We study the robustness of the GHZ (or ``cat'') class of multi-partite states under decoherence. The noise model is described by a general completely positive map for qubits independently coupled to the environment. In particular, the…

Quantum Physics · Physics 2007-05-23 Somshubhro Bandyopadhyay , Daniel A. Lidar

We show that the decoherence, which in the long run destroys quantum features of a system, can be used to reveal the entanglement in a two-qubit system. To this end, we consider a criterion that formally resembles the…

Quantum Physics · Physics 2018-09-07 Jan Krzywda , Piotr Szańkowski , Jan Chwedeńczuk , Łukasz Cywiński

We show that higher order inter-group covariances involving even number of qubits are necessarily positive semidefinite for N qubit separable states, which are completely symmetric under permutations of the qubits. This identification leads…

Quantum Physics · Physics 2009-11-13 A. R. Usha Devi , R. Prabhu , A. K. Rajagopal

It is well-known that observing nonlocal correlations allows us to draw conclusions about the quantum systems under consideration. In some cases this yields a characterisation which is essentially complete, a phenomenon known as…

Quantum Physics · Physics 2020-04-02 Tim Coopmans , Jędrzej Kaniewski , Christian Schaffner

Non-classical probability is the underlying feature of quantum mechanics. The emergence of Bell-CHSH non-locality for bipartite systems and linear entanglement inequalities for two-qubit systems has been shown in Adhikary et al. 2020 [Eur.…

Quantum Physics · Physics 2021-10-22 Sooryansh Asthana , Soumik Adhikary , V. Ravishankar

Contextuality and nonlocality are distinct manifestations at the foundation of quantum mechanics, yet their coexistence within a single quantum state remains subtle. In a hybrid CHSH--KCBS scenario involving the entanglment of a qubit and a…

Quantum Physics · Physics 2026-04-07 Khai Nguyen , Duc M. Doan , Hung Q. Nguyen

Nonlocality is an essential concept that distinguishes quantum from classical models and has been extensively studied in systems of qubits. For higher-dimensional systems, certain results for their two-level counterpart, like Bell…

Quantum Physics · Physics 2025-08-25 Uta Isabella Meyer , Ivan Šupić , Damian Markham , Frédéric Grosshans

While the scaling of entanglement in a quantum system can be used to distinguish many-body quantum phases, it is usually hard to quantify the amount of entanglement in mixed states of open quantum systems, while measuring entanglement…

Statistical Mechanics · Physics 2019-06-04 Katarzyna Macieszczak , Emanuele Levi , Tommaso Macrì , Igor Lesanovsky , Juan P. Garrahan

We investigate the robustness of multiparty nonlocality under local decoherence, acting independently and equally on each subsystems. To be specific, we consider an N-qubit GHZ state under depolarization, dephasing, or dissipation channel,…

Quantum Physics · Physics 2013-05-29 Sung Soon Jang , Yong Wook Cheong , Jaewan Kim , Hai-Woong Lee

We discuss a family of W-class states describing three-qubit systems. For such systems, we analyze the relations between the entanglement measures and the nonlocality parameter for a two-mode mixed state related to the two-qubit subsystem.…

Quantum Physics · Physics 2025-01-08 Joanna K. Kalaga , Wiesław Leoński , Jan Peřina

We present entanglement witnesses for detecting genuine multi-qubit entanglement. Our constructions are robust against noise and require only two local measurement settings, independent of the number of qubits. Thus they allow to verify…

Quantum Physics · Physics 2007-05-23 Geza Toth , Otfried Guehne

Here we investigate the role of quantum interference in the quantum homogenizer, whose convergence properties model a thermalization process. In the original quantum homogenizer protocol, a system qubit converges to the state of identical…

Quantum Physics · Physics 2024-01-15 Anna Beever , Maria Violaris , Chiara Marletto , Vlatko Vedral

The characterization of quantum coherence in the context of quantum information theory and its interplay with quantum correlations is currently subject of intense study. Coherence in an Hamiltonian eigenbasis yields asymmetry, the ability…

Quantum Physics · Physics 2017-03-24 Davide Girolami , Benjamin Yadin

We study the relations between quantum coherence and quantum nonlocality, genuine quantum entanglement and genuine quantum nonlocality. We show that the coherence of a qubit state can be converted to the nonlocality of two-qubit states via…

Quantum Physics · Physics 2019-09-04 Ya Xi , Tinggui Zhang , Zhujun Zheng , Xianqing Li-Jost , Shao-Ming Fei

In a recent work [S. Asthana. New Journal of Physics 24.5 (2022): 053026], we have shown the interrelation of different nonclassical correlations in multiqubit systems with quantum coherence in a single logical qubit. In this work, we…

Quantum Physics · Physics 2023-03-21 Sooryansh Asthana , V. Ravishankar

Identifying non-classicality unambiguously and inexpensively is a long-standing open challenge in physics. The No-Signalling-In-Time protocol was developed as an experimental test for macroscopic realism, and serves as a witness of quantum…

Quantum Physics · Physics 2018-11-28 George C. Knee , Max Marcus , Luke D. Smith , Animesh Datta

Superlocality and superunsteerability provide operational characterization of quantum correlations in certain local and unsteerable states respectively. Such quantum correlated states have a nonzero quantum discord. A two-way nonzero…

Quantum Physics · Physics 2023-10-19 Chellasamy Jebarathinam , Debarshi Das , R. Srikanth

A bipartite state is said to be steerable if and only if it does not have a single system description, i.e., the bipartite state cannot be explained by a local hidden state model. Several steering inequalities have been derived using…

Quantum Physics · Physics 2017-02-01 Debasis Mondal , Tanumoy Pramanik , Arun Kumar Pati

We classify, up to local unitary equivalence, the set of $n$-qubit states that is stabilized by the diagonal subgroup of the local unitary group. We exhibit a basis for this set, parameterized by diagrams of nonintersecting chords…

Quantum Physics · Physics 2008-10-16 David W. Lyons , Scott N. Walck
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