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Experiments on disordered alloys 1 – 3 suggest that spin glasses can be brought into low-energy states faster by annealing quantum fluctuations than by conventional thermal annealing. Owing to the importance of spin glasses as a paradigmatic computational testbed, reproducing this phenomenon in a programmable system has remained a central challenge in quantum optimization 4 – 13 . Here we achieve this goal by realizing quantum-critical spin-glass dynamics on thousands of qubits with a superconducting quantum annealer. We first demonstrate quantitative agreement between quantum annealing and time evolution of the Schrödinger equation in small spin glasses. We then measure dynamics in three-dimensional spin glasses on thousands of qubits, for which classical simulation of many-body quantum dynamics is intractable. We extract critical exponents that clearly distinguish quantum annealing from the slower stochastic dynamics of analogous Monte Carlo algorithms, providing both theoretical and experimental support for large-scale quantum simulation and a scaling advantage in energy optimization. Using a quantum annealing processor to study three-dimensional spin glasses demonstrates an accurate large-scale quantum simulation of critical dynamics and a scaling advantage over analogous classical methods for energy optimization.

The work of Berezinskii, Kosterlitz and Thouless in the 1970s 1 , 2 revealed exotic phases of matter governed by the topological properties of low-dimensional materials such as thin films of superfluids and superconductors. A hallmark of this phenomenon is the appearance and interaction of vortices and antivortices in an angular degree of freedom—typified by the classical XY model—owing to thermal fluctuations. In the two-dimensional Ising model this angular degree of freedom is absent in the classical case, but with the addition of a transverse field it can emerge from the interplay between frustration and quantum fluctuations. Consequently, a Kosterlitz–Thouless phase transition has been predicted in the quantum system—the two-dimensional transverse-field Ising model—by theory and simulation 3 – 5 . Here we demonstrate a large-scale quantum simulation of this phenomenon in a network of 1,800 in situ programmable superconducting niobium flux qubits whose pairwise couplings are arranged in a fully frustrated square-octagonal lattice. Essential to the critical behaviour, we observe the emergence of a complex order parameter with continuous rotational symmetry, and the onset of quasi-long-range order as the system approaches a critical temperature. We describe and use a simple approach to statistical estimation with an annealing-based quantum processor that performs Monte Carlo sampling in a chain of reverse quantum annealing protocols. Observations are consistent with classical simulations across a range of Hamiltonian parameters. We anticipate that our approach of using a quantum processor as a programmable magnetic lattice will find widespread use in the simulation and development of exotic materials. A large-scale programmable quantum simulation is described, using a D-Wave quantum processor to simulate a two-dimensional magnetic lattice in the vicinity of a topological phase transition.

The promise of quantum computing lies in harnessing programmable quantum devices for practical applications such as efficient simulation of quantum materials and condensed matter systems. One important task is the simulation of geometrically frustrated magnets in which topological phenomena can emerge from competition between quantum and thermal fluctuations. Here we report on experimental observations of equilibration in such simulations, measured on up to 1440 qubits with microsecond resolution. By initializing the system in a state with topological obstruction, we observe quantum annealing (QA) equilibration timescales in excess of one microsecond. Measurements indicate a dynamical advantage in the quantum simulation compared with spatially local update dynamics of path-integral Monte Carlo (PIMC). The advantage increases with both system size and inverse temperature, exceeding a million-fold speedup over an efficient CPU implementation. PIMC is a leading classical method for such simulations, and a scaling advantage of this type was recently shown to be impossible in certain restricted settings. This is therefore an important piece of experimental evidence that PIMC does not simulate QA dynamics even for sign-problem-free Hamiltonians, and that near-term quantum devices can be used to accelerate computational tasks of practical relevance. Experimental demonstration of quantum speedup that scales with the system size is the goal of near-term quantum computing. Here, the authors demonstrate such scaling advantage for a D-Wave quantum annealer over analogous classical algorithms in simulations of frustrated quantum magnets.

In this paper we study a kind of operator —known as credibility-limited base revisions— which addresses two of the main issues that have been pointed out to the AGM model of belief change. Indeed, on the one hand, these operators are defined on belief bases (rather than belief sets) and, on the other hand, they are constructed with the underlying idea that not all new information is accepted. We propose twenty different classes of credibility-limited base revision operators and obtain axiomatic characterizations for each of them. Additionally we thoroughly investigate the interrelations (in the sense of inclusion) among all those classes. More precisely, we analyse whether each one of those classes is or is not (strictly) contained in each of the remaining ones.

This paper seeks to provide a continuous measure to represent the distance between skills acquired in tertiary education and those required in an individual's occupation. This distance measure, which is computed by combining data from the 2010 Brazilian census with information from the 2010 Brazilian classification of occupations, suggests that workers usually classified in most of the literature into a single group of mismatches are in fact quite heterogeneous in the way their occupations are associated with areas of study. Evidence also shows that, even among mismatched workers, hourly labor earnings tend to decrease as the distance measure increases. This indicates the labor earnings penalty is not the same for all mismatched workers, seemingly changing substantially depending on the level of similarity between occupation and field of study.

In this paper, we propose and axiomatically characterize residual contractions, a new kind of contraction operators for belief bases. We establish that the class of partial meet contractions is a strict subclass of the class of residual contractions. We identify an extra condition that may be added to the definition of residual contractions, which is such that the class of residual contractions that satisfy it coincides with the class of partial meet contractions. We investigate the interrelations in the sense of (strict) inclusion among the class of residual contractions and other classes of well known contraction operators for belief bases.

Purpose The purpose of this paper is to investigate the relationship between educational mismatch and labor earnings in Brazil, taking into account individual fixed effects. Design/methodology/approach The empirical analysis employs longitudinal data and information provided by job analysts about the schooling required for each occupation. The latter of which is used to classify workers as undereducated, overeducated, or adequately matched. Estimates include individual fixed effects to control for time-invariant unobserved heterogeneity. Findings Evidence indicates that one more year of overeducation increases labor earnings, but only half as strong as one more year of required schooling. The estimated effects on years of undereducation are negative, but undereducated workers earn more than adequately matched workers with the same level of education. Although, in particular, the incidence of undereducation in Brazil is much higher than reported for developed countries, the impact of over- and undereducation does not differ. Research limitations/implications The fixed effects approach only controls for unobservable factors that are time-invariant. Also, much lower impacts using fixed effects may be due in part to attenuation bias as a consequence of measurement errors. Originality/value This study contributes to the scarce literature on the consequences of overeducation and undereducation for labor earnings in developing countries, providing estimates that take into account individual fixed effects.

This paper investigates whether parents’ entry into unemployment affects investment in children’s education through their decision to provide public or private education for their children. The empirical approach makes use of longitudinal data from the Continuous National Household Sample Survey ( Pesquisa Nacional por Amostra de Domicílios Contínua –PNAD contínua) and propensity-score matching with difference-in-difference methods. According to estimates, parents’ unemployment reduces the probability of children’s enrollment in the private educational system, which usually has better quality but high costs, instead of in the public educational system, which is offered for free but typically has poor quality. Thus, evidence suggests that reductions in household income as a consequence of unemployment can have impacts on the quality of human capital accumulated by children.

The danger of ionizing radiation exposure to human health is a concern. Since its wide use in medicine and industry, the development of radioprotectors has been very significant. Adenosine exerts anti-inflammatory actions and promotes tissue protection and repair, by activating the P1 receptors (A 1 , A 2A , A 2B , and A 3 ). Zebrafish ( Danio rerio ) is an appropriate tool in the fields of toxicology and pharmacology, including the evaluation of radiobiological outcomes and in the search for radioprotector agents. This study aims to evaluate the effect of adenosine in the toxicity induced by radiation in zebrafish. Embryos were treated with 1, 10, or 100 µM adenosine, 30 min before the exposure to 15 Gy of gamma radiation. Adenosine potentiated the effects of radiation in heart rate, body length, and pericardial edema. We evaluated oxidative stress, tissue remodeling and inflammatory. It was seen that 100 µM adenosine reversed the inflammation induced by radiation, and that A 2A2 and A 2B receptors are involved in these anti-inflammatory effects. Our results indicate that P1R activation could be a promising pharmacological strategy for radioprotection.

Traditional land use may play a key role in conserving and promoting ecosystem integrity. However, little is known about conserving genetic diversity in such traditional management systems. The Brazilian pine (Araucaria angustifolia) is an important element of traditionally managed landscapes in southern Brazil but is currently considered at risk of extinction. In order to assess the contribution of traditional management systems in conserving the Brazilian pine, we compared genetic diversity descriptors between traditionally used and protected populations. To accomplish this, we compared four managed populations against two protected populations in southern Brazil, using allozyme markers to estimate genetic indexes. All studied populations presented similar levels of genetic diversity and magnitude of outcrossing, indicating the potential for conserving the genetic diversity of A. angustifolia populations in traditionally managed land use systems. Traditional management systems should be considered in conservation strategies for Araucaria Forest because they help maintaining the genetic diversity of keystone species, while keeping cultural practices alive. O uso traditional da terra pode contribuir para conservar e promover a integridade dos ecossistemas. No entanto, pouco se sabe sobre a conservção da diversidade genética em tais sistemas de manejo. O pinheiro-brasileiro (Araucaria angustifolia) é um importante elemento das paisagens tradicionalmente manejadas no sul do Brasil, mas é considerado ameaçado de extinçao. Com o objetivo de avaliar a contribuição dos sistemas tradicionais de manejo na conservação do pinheiro-brasileiro, foram comparados descritores da diversidade genética entre populações tradicionalmente manejadas e populações protegidas. Para tanto, foram comparadas quatro populações manejadas com duas populações protegidas no sul do Brasil, utilizando marcadores alozímicos para estimar os indices genéticos. Todas as populações estudadas apresentaram níveis semelhantes de diversidade genética e taxas de cruzamento, indicando que os sistemas tradicionais de manejo apresentam potencial para conservar a diversidade genética de populações de A. angustifolia. Os sistemas tradicionais de manejo devem ser considerados nas estratégias de conservagção da Floresta de Araucária, pois ajudam a manter a diversidade genética de espécies-chave, como A. angustifolia, e mantêm vivas as práticas culturais.