NMR analog of Bell's inequalities violation test

Souza, Alexandre M.; Magalhães, Alviclér; Teles, J.; deAzevedo, Eduardo R.; Bonagamba, Tito J.; Sarthour, R. S.

doi:10.1088/1367-2630/10/3/033020

Cited by 24 publications

(25 citation statements)

References 39 publications

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“…In particular, Bell's inequalities violations are related to the security of cryptography protocols [15] and are a necessary and sufficient condition to the usefulness of quantum states in communication complexity protocols [14]. A Bell's inequality test for two qubits involves measurements of a set of correlations functions, which for a magnetic system are the correlations of the magnetic moments along specific directions [36]. For a system with two spin 1/2, the test involves the measurement of the mean value of the Bell operator given by:…”

Section: Entanglementmentioning

confidence: 99%

Entanglement and Bell’s inequality violation above room temperature in metal carboxylates

et al. 2009

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In the present work we show that a special family of materials, the metal carboxylates, may have entangled states up to very high temperatures. From magnetic susceptibility measurements, we have estimated the critical temperature below which entanglement exists in the cooper carboxylate {Cu2(O2CH)4}{Cu(O2CH)2(2-methylpyridine)2}, and we have found this to be above room temperature (Te ∼ 630 K). Furthermore, the results show that the system remains maximally entangled until close to ∼ 100 K and the Bell's inequality is violated up to nearly room temperature (∼ 290 K).

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Section: Entanglementmentioning

confidence: 99%

Entanglement and Bell’s inequality violation above room temperature in metal carboxylates

et al. 2009

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“…It has been used in an inventive way for NMR methods and contributed to the impressive and fast success of the technique in QIP [1,2]. NMR also allows, through the manipulation of nuclear spin qubits, the simulation of more complex systems [47][48][49][50][51].…”

Section: Final Discussionmentioning

confidence: 99%

On the quantumness of correlations in nuclear magnetic resonance

Soares-Pinto

Auccaise

Maziero

et al. 2012

Phil. Trans. R. Soc. A.

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Nuclear magnetic resonance (NMR) was successfully employed to test several protocols and ideas in quantum information science. In most of these implementations, the existence of entanglement was ruled out. This fact introduced concerns and questions about the quantum nature of such bench tests. In this paper, we address some issues related to the non-classical aspects of NMR systems. We discuss some experiments where the quantum aspects of this system are supported by quantum correlations of separable states. Such quantumness, beyond the entanglement-separability paradigm, is revealed via a departure between the quantum and the classical versions of information theory. In this scenario, the concept of quantum discord seems to play an important role. We also present an experimental implementation of an analogue of the single-photon MachZehnder interferometer employing two nuclear spins to encode the interferometric paths. This experiment illustrates how non-classical correlations of separable states may be used to simulate quantum dynamics. The results obtained are completely equivalent to the optical scenario, where entanglement (between two field modes) may be present.

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“…If the unobserved spins behaved in the same way as the observed spins, they would become observable-giving a contradiction. When authoring a previous paper [10] (their [23]), SOS and coauthors claim to have simulated the violation of a Bell inequality with a room-temperature NMR experiment-precisely because of the failure of the fair sampling hypothesis. In contrast, in the work under consideration here, despite the experimental system being the same, SOS do not regard their experiment as a simulation.…”

Section: The Sampling Is Unfairmentioning

confidence: 99%

Comment on ‘A scattering quantum circuit for measuring Bell's time inequality: a nuclear magnetic resonance demonstration using maximally mixed states’

et al. 2012

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A recent paper by Souza, Oliveira and Sarthour (SOS) reports the experimental violation of a Leggett-Garg (LG) inequality (sometimes referred to as a temporal Bell inequality). The inequality tests for quantum mechanical superposition: if the inequality is violated, the dynamics cannot be explained by a large class of classical theories under the heading of macrorealism. Experimental tests of the LG inequality are beset by the difficulty of carrying out the necessary so-called 'non-invasive' measurements (which for the macrorealist will extract information from a system of interest without disturbing it). SOS argue that they nevertheless achieve this difficult goal by putting the system in a maximally mixed state. The system then allegedly undergoes no perturbation during their experiment. Unfortunately, the method is ultimately unconvincing to a skeptical macrorealist and so the conclusions drawn by SOS are unjustified.

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NMR analog of Bell's inequalities violation test

Cited by 24 publications

References 39 publications

Entanglement and Bell’s inequality violation above room temperature in metal carboxylates

Entanglement and Bell’s inequality violation above room temperature in metal carboxylates

On the quantumness of correlations in nuclear magnetic resonance

Comment on ‘A scattering quantum circuit for measuring Bell's time inequality: a nuclear magnetic resonance demonstration using maximally mixed states’

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