2,285 research outputs found
Violation of a Leggett-Garg inequality with ideal non-invasive measurements
No full textThe quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system, which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realization using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble.</p
Comment on 'A scattering quantum circuit for measuring Bell's time inequality:a nuclear magnetic resonance demonstration using maximally mixed states'
No full textA 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.</p
Nobel Laureate Anthony J Leggett: A scientometric portrait
No full textThis paper attempts to analyse the publication productivity of Anthony J. Leggett, the 2003 Nobel Prize winner in physics. His contributions peaked in 1987, 1994, and 1998 with 10 papers each. He had 194 publications during 1964 - 2004 in domains like Superfluid 3He (65), Foundations of Quantum Mechanics (36), Dissipative Quantum Systems (24), Atomic Alkali Gases (18), and Miscellaneous (51)which were analysed for authorship pattern with his 70 collaborators. Most active collaborators with Anthony J Leggett were: A. Garg with six papers and A. O. MCaldeira, D. M. Ginsberg, D. J. Vanharlingen , F. Sols, S.Takagi and D. A. Wollman with five papers each. His productivity coefficient was 0.60 which clearly indicates that his productivity
increased after 50 percentile age. The highest degree of collaboration (1) for Anthony J. Leggett was found during 1964, 1971 and 1983. Journals have been the most preferred channel of communication, where as many as 139 papers out of 194 have been published. The core journals publishing his papers were: Phys. Rev. Leu. (42), Phys. Rev. B (9), J. Low Temp. Phys. (8),Phys. Rev. A (7), Ann. Phys. (6), Foundations of physics (6), J. Phys.(5), Prog. Theor: Phys. (5), and Rev. Mod. Phys. (5).Publication density was 3.02 and publication concentration was 3.59
R. Leggett Plumbing and Heating / Jos. C. Cahoon
No full textAdvertisement for R. Leggett Plumbing and Heating; Jos. C. Cahoon, dealer in coal, lumber & hardware, 300 West Lovendah
Quantum Nondemolition Measurement Enables Macroscopic Leggett-Garg Tests
No full textWe show how a test of macroscopic realism based on Leggett-Garg inequalities (LGIs) can be performed in a macroscopic system. Using a continuous-variable approach, we consider quantum nondemolition (QND) measurements applied to atomic ensembles undergoing magnetically driven coherent oscillation. We identify measurement schemes requiring only Gaussian states as inputs and giving a significant LGI violation with realistic experimental parameters and imperfections. The predicted violation is shown to be due to true quantum effects rather than to a classical invasivity of the measurement. Using QND measurements to tighten the “clumsiness loophole” forces the stubborn macrorealist to recreate quantum backaction in his or her account of measurement
The new test for dishonesty in criminal law – lessons from the courts of equity?
No full textThe Supreme Court decision in Ivey v Genting Casinos rejected the two stage test for dishonesty set out in R v Ghosh and replaced it with a single, objective test which transcends both criminal and civil law. This article asks whether it was correct to create a single test for dishonesty and in doing so, what role will subjectivity now play in the criminal law’s application of what is considered dishonest behaviour. Historically, the civil courts have beset with confusion as to the role of subjectivity in the test for dishonesty in light of Royal Brunei Airlines v Tan. The author will consider whether lessons can be learned from the civil courts and whether similar problems will trouble criminal law, particularly in light of criticism of the Ivey test and a preference, by some, for subjectivity to play a greater role in criminal liability for theft and other dishonesty offences
William Leggett, Neglected Figure of American Literary History
No full text This account of Leggett and his better known associate, William Cullen Bryant, is written by a member of the English faculty at Brooklyn College. Dr. Glicksberg is the author of Walt Whitman and the Civil War. He has written for many literary journals. </jats:p
Macrorealism from entropic Leggett-Garg inequalities
No full textOpen AccessWe formulate entropic Leggett-Garg inequalities, which place constraints on the statistical outcomes of temporal correlations of observables. The information theoretic inequalities are satisfied if macrorealism holds. We show that the quantum statistics underlying correlations between time-separated spin component of a quantum rotor mimics that of spin correlations in two spatially separated spin-s particles sharing a state of zero total spin. This brings forth the violation of the entropic Leggett-Garg inequality by a rotating quantum spin-s system in a similar manner as does the entropic Bell inequality [ S. L. Braunstein and C. M. Caves Phys. Rev. Lett. 61 662 (1988)] by a pair of spin-s particles forming a composite spin singlet state
Enhanced violations of Leggett-Garg inequalities in an experimental three-level system
No full textLeggett-Garg inequalities are tests of macroscopic realism that can be violated by quantum mechanics. In this letter, we realise photonic Leggett-Garg tests on a three-level system and implement measurements that admit three distinct measurement outcomes, rather than the usual two. In this way we obtain violations of three- and four-time Leggett-Garg inequalities that are significantly in excess of those obtainable in standard Leggett-Garg tests. We also report violations the quantum-witness equality up to the maximum permitted for a three-outcome measurement. Our results highlight differences between spatial and temporal correlations in quantum mechanics
Evaluation and updates to the Leggett model for pharmacokinetic modeling of exposure to lead in the workplace – Part II adjustments to the adult exposure model, confirmation of Leggett+, and modeling of workplace exposure
No full textCalifornia’s Office of Environmental Health Hazard Assessment has updated the comprehensive age-specific model of lead metabolism in humans published by Richard W. Leggett in 1993. The updated model, called Leggett+, was introduced in a peer-reviewed report in 2013. The Leggett + model simulates the relationship between blood lead and exposure in the workplace. Leggett + includes a workplace exposure model comprising respiratory tract intake (workplace lead inhaled by a worker) and uptake (lead absorbed into the blood from the respiratory tract plus uptake from ambient air and diet). The latter is calculated as intake times an inhalation transfer coefficient plus background uptake. An adjusted adult systemic model describes the metabolism of the absorbed lead. This paper provides details about the workplace exposure and uptake elements of Leggett+, an updated approach to calibrating an inhalation transfer coefficient, confirmation of the model’s performance in predicting blood lead levels from workplace studies, and predictions of blood lead levels from simulated exposures to workplace airborne lead over a working lifetime. Blood lead relative to airborne lead concentrations in a standard workplace scenario predicted by Leggett + was similar to corresponding relationships from four published workplace studies. Leggett + predictions displayed a good fit to regression equations when other key factors were considered such as pre-employment blood lead and ongoing background intake of lead, workplace air concentration, lead aerosol characteristics, and worker activity levels. The comprehensive Leggett + model can simulate plausible workplace air–blood lead relationships from a broad range of worker exposures. The inhalation transfer coefficient of 0.30, derived from empirical data described in the 2013 report has been reexamined. The original estimate continues to represent a plausible mid-point for a coefficient derived from an expanded range of theoretical particle size distributions deposited in the upper and lower regions of the respiratory tract considering intake during sedentary and outdoor activity breathing scenarios. This coefficient is slightly lower than the value of 0.35 estimated for unknown forms of lead by Leggett in 1993.</p
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