The work of Berezinskii, Kosterlitz and Thouless in the 1970s 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. 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.

Understanding magnetic phases in quantum mechanical systems is one of the essential goals in condensed matter physics, and the advent of prototype quantum simulation hardware has provided new tools for experimentally probing such systems. We report on the experimental realization of a quantum simulation of interacting Ising spins on three-dimensional cubic lattices up to dimensions 8 × 8 × 8 on a D-Wave processor (D-Wave Systems, Burnaby, Canada). The ability to control and read out the state of individual spins provides direct access to several order parameters, which we used to determine the lattice's magnetic phases as well as critical disorder and one of its universal exponents. By tuning the degree of disorder and effective transverse magnetic field, we observed phase transitions between a paramagnetic, an antiferromagnetic, and a spin-glass phase.

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Euterpe edulis (Martius) is a single‐stemmed, abundant Neotropical palm of the Brazilian Atlantic Forest (Mata Atlântica). The species produces the heart of palm, locally called palmito, which is an important source of income for forest owners. Because of its high market value, its short‐term demands of the forest environment, and its important interactions with animal species, this palm is suitable for sustainable management and conservation purposes. In this paper, we present the results from a 15‐year investigation of this species, synthesizing results on its demography, seed dispersion, reproductive biology, genetics, and economics. We have linked these results in a proposal for the species' sustainable management and conservation.

Hamiltonian-based quantum computation is a class of quantum algorithms in which the problem is encoded in a Hamiltonian and the evolution is performed by a continuous transformation of the Hamiltonian. Universal adiabatic quantum computing, quantum simulation, and quantum annealing are examples of such algorithms. Up to now, all implementations of this approach have been limited to qubits coupled via a single degree of freedom. This gives rise to a stoquastic Hamiltonian that has no sign problem in quantum Monte Carlo simulations. In this paper, we report implementation and measurements of two superconducting flux qubits coupled via two canonically conjugate degrees of freedom-charge and flux-to achieve a nonstoquastic Hamiltonian. We perform microwave spectroscopy to extract circuit parameters and show that the charge coupling manifests itself as a σ y σ y interaction in the computational basis. We observe destructive interference in quantum coherent oscillations between the computational basis states of the two-qubit system. Finally, we show that the extracted Hamiltonian is nonstoquastic over a wide range of parameters.

-(Reproductive phenology and seed production of Araucaria angustifolia (Bert.) O. Kuntze). The knowledge about the reproductive phenology of Araucaria angustifolia has applications to the seed harvest for "ex situ" conservation, for commercial use of the seeds and to understand the dynamic and regeneration of its natural populations. The reproductive phenology and seed production of A. angustifolia were evaluated for a natural population occurring at Parque Estadual Campos de Jordão, São Paulo State, Brazil. The present study investigates: (i) how is the reproductive cycle and the phenological pattern of araucaria? (ii) how is the potential of seed production and its variability? Sixty adult plants (30 males and 30 females) were marked for phenological observations. Seed production was estimated based on the number of female plants in a 10 ha area, number of cones per plant, number of seeds per cone and seed weight. The reproductive cycle of A. angustifolia extended for 20 to 24 months, from the observation of the first cone to seed fall. The pollination occurred between September and October and seed maturation and seed fall from March to June. Seed production was significantly different between years (117 kg.ha -1 in 2001 e 160 kg.ha -1 in 2002). The duration of ripe seed offer was also different between years. The variation observed in the amount and availability of seeds suggests that the observation of reproductive phenology and estimation of seed production are important to guide strategies for conservation and management of this resource.Key words -Araucaria angustifolia, Araucaria forest, reproductive phenology, seed production RESUMO -(Fenologia reprodutiva e produção de sementes em Araucaria angustifolia (Bert.) O. Kuntze). O estudo da fenologia reprodutiva de A. angustifolia tem aplicação na coleta de sementes destinadas à conservação de germoplasma, à obtenção de sementes para fins comerciais e ao entendimento da dinâmica de regeneração das populações naturais. Este trabalho teve como objetivo investigar a fenologia reprodutiva em uma população natural de A. angustifolia localizada no Parque Estadual Campos do Jordão, SP, procurando entender: (i) Qual é o seu ciclo reprodutivo e o comportamento fenológico? (ii) Como varia e qual o potencial de produção de sementes desta espécie? Para o acompanhamento da fenologia reprodutiva foram marcados 60 indivíduos (30 masculinos e 30 femininos), observados de novembro de1999 a agosto de 2002. A produção de sementes foi estimada com base na contagem do número de plantas femininas, número de estróbilos por planta, número de sementes por estróbilo e peso de sementes. O ciclo reprodutivo da A. angustifolia foi de 20 a 24 meses, do aparecimento dos estróbilos até a queda das sementes. A polinização ocorreu entre setembro e outubro e a maturação e queda das sementes de março a junho. A produção de sementes mostrou diferença significativa entre os anos (117 kg.ha -1 em 2001 e 160 kg.ha -1 em 2002) e a duração da oferta foi distinta entre anos. As variações na...

ABSTRACT. South American Araucaria species include Araucaria araucana (Mol.) C. Koch (Argentina and Chile) and Araucaria angustifolia (Bert.) O. Kuntze (Brazil and Argentina). Both species produce nut-like seeds (piñones, pinhões) that have, since preColumbian times, formed part of the traditional diet of local societies: Kaingang (A. angustifolia) and Mapuche-Pehuenche (A. araucana). In this work, we compared and analyzed converging and diverging characteristics of these species founded on ecological and ethnobotanical evidence. We also studied the role of human groups in the construction of Araucaria forests. The methodology used was based on a bibliographical analysis that included a wide range of sources, from ecological to social sciences. Our results show that both species hold strong cultural and symbolic significance for associated human groups. The ecological characteristics of both species have favored their rapid territorial expansion since the Holocene; however, palynological, archaeological, and ethnobotanical evidence reinforces the hypothesis that the human groups involved played a key role in this process. For both societies, there are records of past and present practices related to the transport, storage, and processing of the seeds. The landscapes where A. araucana and A. angustifolia are present also reflect use patterns that hold a level of significance that goes beyond merely utilitarian purposes. For the Kaingang and the Mapuche-Pehuenche, the Araucaria forests are associated with the concept of territoriality and play a key role in determining their identity. Our approach to cultural landscapes, which considers the importance of societies in the modelling of natural landscapes, can offer new perspectives for conservation policies and action in both forests.

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.