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We report on the experimental violation of multipartite Bell inequalities by entangled states of trapped ions. First we consider resource states for measurement-based quantum computation of between 3 and 7 ions and show that all strongly…

Quantum Physics · Physics 2014-03-19 B. P. Lanyon , M. Zwerger , P. Jurcevic , C. Hempel , W. Dür , H. J. Briegel , R. Blatt , C. F. Roos

A family of Bell-type inequalities is present, which are constructed directly from the "standard" Bell inequalities involving two dichotomic observables per site. It is shown that the inequalities are violated by all the generalized…

Quantum Physics · Physics 2007-05-23 Zeqian Chen

Techniques developed for device-independent characterizations allow one to certify certain physical properties of quantum systems without assuming any knowledge of their internal workings. Such a certification, however, often relies on the…

Quantum Physics · Physics 2019-07-03 Pei-Sheng Lin , Jui-Chen Hung , Ching-Hsu Chen , Yeong-Cherng Liang

The quantum Fisher information (QFI) of certain multipartite entangled quantum states is larger than what is reachable by separable states, providing a metrological advantage. Are these nonclassical correlations strong enough to potentially…

Quantum Physics · Physics 2019-05-03 Florian Fröwis , Matteo Fadel , Philipp Treutlein , Nicolas Gisin , Nicolas Brunner

By introducing a quantitative `degree of commutativity' in terms of the angle between spin-observables we present two tight quantitative trade-off relations in the case of two qubits: First, for entangled states, between the degree of…

Quantum Physics · Physics 2007-10-09 Michael Seevinck , Jos Uffink

The problem of closing the detection loophole in Bell tests is investigated in the presence of a limited number of efficient detectors using emblematic multipartite quantum states. To this end, a family of multipartite Bell inequalities is…

Quantum Physics · Physics 2018-08-17 Kamil Kostrzewa , Wieslaw Laskowski , Tamas Vertesi

Local measurements acting on entangled quantum states give rise to a rich correlation structure in the multipartite scenario. We introduce a versatile technique to build families of Bell inequalities witnessing different notions of…

Quantum Physics · Physics 2019-03-27 Florian J. Curchod , Mafalda L. Almeida , Antonio Acín

Current understanding of correlations and quantum phase transitions in many-body systems has significantly improved thanks to the recent intensive studies of their entanglement properties. In contrast, much less is known about the role of…

Quantum Physics · Physics 2017-05-02 J. Tura , A. B. Sainz , T. Grass , R. Augusiak , A. Acín , M. Lewenstein

To reproduce in a local hidden variables theory correlations that violate Bell inequalities, communication must occur between the parties. We show that the amount of violation of a Bell inequality imposes a lower bound on the average…

Quantum Physics · Physics 2007-10-22 Stefano Pironio

We describe a method of extending Bell inequalities from $n$ to $n+1$ parties and formulate sufficient conditions for our method to produce tight inequalities from tight inequalities. The method is non trivial in the sense that the…

Quantum Physics · Physics 2008-05-06 Yu-Chun Wu , Piotr Badziag , Marcin Wieśniak , Marek Żukowski

In this paper we propose a general method to quantify how "quantum" a set of quantum states is. The idea is to gauge the quantumness of the set by the worst-case difficulty of transmitting the states through a purely classical communication…

Quantum Physics · Physics 2007-05-23 Christopher A. Fuchs , Masahide Sasaki

Quantum nonlocality as a witness of entanglement plays a crucial role in various fields. Existing quantum monogamy relations rule out the possibility of simultaneous violations of any Bell inequalities with partial statistics generated from…

Quantum Physics · Physics 2024-03-15 Yan-Han Yang , Xin-Zhu Liu , Xing-Zhou Zheng , Shao-Ming Fei , Ming-Xing Luo

Bell's theorem is typically understood as the proof that quantum theory is incompatible with local-hidden-variable models. More generally, we can see the violation of a Bell inequality as witnessing the impossibility of explaining quantum…

Any Quantum Key Distribution (QKD) protocol consists first of sequences of measurements that produce some correlation between classical data. We show that these correlation data must violate some Bell inequality in order to contain…

Quantum Physics · Physics 2009-11-11 Antonio Acin , Nicolas Gisin , Lluis Masanes

We resolve an old problem about the existence of hidden parameters in a three-dimensional quantum system by constructing an appropriate Bell's type inequality. This reveals a nonclassical nature of most spin-$1$ states. We shortly discuss…

Quantum Physics · Physics 2009-11-13 Alexander A. Klyachko , M. Ali Can , Sinem Binicioğlu , Alexander S. Shumovsky

We propose an experiment to test Bell's inequality violation in condensed-matter physics. We show how to generate, manipulate and detect entangled states using ballistic electrons in Coulomb-coupled semiconductor quantum wires. Due to its…

Quantum Physics · Physics 2009-11-06 Radu Ionicioiu , Paolo Zanardi , Fausto Rossi

Classical and quantum physics impose different constraints on the joint probability distributions of observed variables in a causal structure. These differences mean that certain correlations can be certified as non-classical, which has…

Quantum Physics · Physics 2020-07-22 V. Vilasini , Roger Colbeck

The state of a quantum system, consisting of two distinct subsystems, is called separable if it can be prepared by two distant experimenters who receive instructions from a common source, via classical communication channels. A necessary…

Quantum Physics · Physics 2009-10-30 Asher Peres

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

We derive exceedingly simple practical procedures revealing the quantum nature of states and measurements by the violation of classical upper bounds on the statistics of arbitrary measurements. Data analysis is minimum and definite…

Quantum Physics · Physics 2009-04-28 Ángel Rivas , Alfredo Luis