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Quantum steering can be detected via the violation of steering inequalities, which provide sufficient conditions for the steerability of quantum states. Here we discuss the converse problem, namely ensuring that a state is unsteerable, and…

Quantum Physics · Physics 2016-03-21 Joseph Bowles , Flavien Hirsch , Marco Túlio Quintino , Nicolas Brunner

Among various definitions of quantum correlations, quantum discord has attracted considerable attention. To find analytical expression of quantum discord is an intractable task. Exact results are known only for very special states, namely,…

Quantum Physics · Physics 2015-05-27 Mingjun Shi , Fengjian Jiang , Chunxiao Sun , Jiangfeng Du

We study the mathematical structures and relations among some quantities in the theory of quantum entanglement, such as separability, weak Schmidt decompositions, Hadamard matrices etc.. We provide an operational method to identify the…

Quantum Physics · Physics 2014-02-26 Bobo Hua , Shaoming Fei , Juergen Jost , Xianqing Li-Jost

The counterintuitive effect of non-unique ordering of two-qubit states with quantum entanglement measures was discovered over ten years ago. More precisely, it was shown by Monte Carlo simulations that there exist states for which the…

Quantum Physics · Physics 2012-07-17 Małgorzata Okrasa , Zbigniew Walczak

We explore the possibility of using "weak" measurements to carry out quantum state tomography. Given a certain fixed number of copies of identically prepared states of a qubit, we simulate state tomography using weak as well as projective…

Quantum Physics · Physics 2014-08-06 Debmalya Das , Arvind

Measurement in quantum mechanics is generally described as an irreversible process that perturbs the wavefunction describing a quantum system. In this work we establish a formal connection between the measurement description within the…

Quantum Physics · Physics 2016-05-17 Fabio L. Traversa , Guillermo Albareda

We address the question of the role of quantum correlations beyond entanglement in context of quantum magnetometry. To this end, we study the evolution of the quantum discord, measured by the rescaled discord, of two electron-spin qubits…

Quantum Physics · Physics 2015-06-12 Paweł Mazurek , Katarzyna Roszak , Paweł Horodecki

The concept of quantum discord aims at unveiling quantum correlations that go beyond those described by entanglement. Its original formulation [J. Phys. A 34, 6899 (2001); Phys. Rev. Lett 88, 017901 (2002)] is difficult to compute even for…

Bell inequality is a mathematical inequality derived using the assumptions of locality and realism. Its violation guarantees the existence of quantum correlations in a quantum state. Bell inequality acts as an entanglement witness in the…

Quantum Physics · Physics 2016-07-29 Kaifeng Bu , Asutosh Kumar , Junde Wu

We demonstrate that quantum correlations can emerge from the statistical correlations of random discrete models, without an a priori assumption that the random models are quantum mechanical in nature, that is without considering…

Disordered Systems and Neural Networks · Physics 2023-05-05 Ioannis Kleftogiannis , Ilias Amanatidis

Quantum correlations exhibit behaviour that cannot be resolved with a local hidden variable picture of the world. In quantum information, they are also used as resources for information processing tasks, such as Measurement-based Quantum…

Quantum Physics · Physics 2011-02-10 Matty J. Hoban , Earl T. Campbell , Klearchos Loukopoulos , Dan E. Browne

Discord and entanglement characterize two kinds of quantum correlations, and discord captures more correlation than entanglement in the sense that even separable states may have nonzero discord. In this paper, we propose a new kind of…

Quantum Physics · Physics 2015-06-02 Jianwei Xu

We analyze the general nonclassicality of correlations of a composite quantum systems as measured by the negativity of quantumness. The latter corresponds to the minimum entanglement, as quantified by the negativity, that is created between…

Quantum Physics · Physics 2013-07-31 Takafumi Nakano , Marco Piani , Gerardo Adesso

Quantum resources can improve communication complexity problems (CCPs) beyond their classical constraints. One quantum approach is to share entanglement and create correlations violating a Bell inequality, which can then assist classical…

This short article concentrates on the conceptual aspects of the violation of Bell inequalities, and acts as a map to the 265 cited references. The article outlines (a) relevant characteristics of quantum mechanics, such as statistical…

Quantum Physics · Physics 2021-06-29 Brian Drummond

Quantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the…

Quantum Physics · Physics 2019-08-21 Matthew A. Hunt , Igor V. Lerner , Igor V. Yurkevich , Yuval Gefen

The notion of distance defined on the set of states of a composite quantum system can be used to quantify total, quantum and classical correlations in a unifying way. We provide new closed formulae for classical and total correlations of…

Quantum Physics · Physics 2014-09-25 Thomas R. Bromley , Marco Cianciaruso , Rosario Lo Franco , Gerardo Adesso

We demonstrate a hierarchy of various classes of quantum correlations on experimentally prepared two-qubit Werner-like states with controllable white noise. Werner states, which are white-noise-affected Bell states, are prototypal examples…

The aim of this chapter is to describe two situations where positive noise correlations can be directly monitored using a transport experiment, either with a superconductor or with a correlated electron system. To be more precise, the…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 T. Martin , A. Crepieux , N. Chtchelkatchev

The effect of quantum steering arises from the judicious combination of an entangled state with a set of incompatible measurements. Recently, it was shown that this form of quantum correlations can be quantified in terms of a dimension,…