Experimental investigation of linear-optics-based quantum target detection

The development of new techniques to improve measurements is crucial for all sciences. By employing quantum systems as sensors to probe some physical property of interest allows the application of quantum resources, such as coherent superpositions and quantum correlations, to increase measurement precision. Here we experimentally investigate a scheme for quantum target detection based on linear optical measurment devices, when the object is immersed in unpolarized background light. By comparing the quantum (polarization-entangled photon pairs) and the classical (separable polarization states), we found that the quantum strategy provides us an improvement over the classical one in our experiment when the signal to noise ratio is greater than 1/40, or about 16dB of noise. This is in constrast to quantum target detection considering non-linear optical detection schemes, which have shown resilience to extreme amounts of noise. A theoretical model is developed which shows that, in this linear-optics context, the quantum strategy suffers from the contribution of multiple background photons. This effect does not appear in our classical scheme. By improving the two-photon detection electronics, it should be possible to achieve a polarization-based quantum advantage for a signal to noise ratio that is close to 1/400 for current technology.Comment: comments are welcome, submitted to PR

Transient Charging and Discharging of Spin-polarized Electrons in a Quantum Dot

We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance (TMR) are calculated using both nonequilibrium Green function and master equation techniques. Both parallel and antiparallel leads' magnetization alignments are analyzed. Our main findings are: a dynamical spin accumulation that changes sign in time, a short-lived pulse of spin polarized current in the emitter lead (but not in the collector lead), and a dynamical TMR that develops negative values in the transient regime. We also observe that the intra-dot Coulomb interaction can enhance even further the negative values of the TMR.Comment: 7 pages, 6 figures. Typos corrections corresponding to the published versio

Posição de estufas de polietileno e potenciais de água no solo no cultivo do melão rendilhado híbrido 'Nero'.

O objetivo deste trabalho foi verificar os efeitos de quatro diferentes tens?es de água no solo (-30, -40, -50 e -70 kPa) e posições de estufa (Norte-Sul e Leste-Oeste) sobre o produção e qualidade de frutos de mel?o rendilhado. O fator posição da estufa influenciou o diâmetro, comprimento, rendimento de polpa, teor de sólidos solúveis totais e peso médio de frutos. O fator potencial de água no solo afetou apenas o teor de sólidos solúveis totais.Suplemento. Edição de Resumos do 43 Congresso Brasileiro de Olericultura, Recife, jul. 2003

Research in Geant4 electromagnetic physics design, and its effects on computational performance and quality assurance

The Geant4 toolkit offers a rich variety of electromagnetic physics models; so far the evaluation of this Geant4 domain has been mostly focused on its physics functionality, while the features of its design and their impact on simulation accuracy, computational performance and facilities for verification and validation have not been the object of comparable attention yet, despite the critical role they play in many experimental applications. A new project is in progress to study the application of new design concepts and software techniques in Geant4 electromagnetic physics, and to evaluate how they can improve on the current simulation capabilities. The application of a policy-based class design is investigated as a means to achieve the objective of granular decomposition of processes; this design technique offers various advantages in terms of flexibility of configuration and computational performance. The current Geant4 physics models have been re-implemented according to the new design as a pilot project. The main features of the new design and first results of performance improvement and testing simplification are presented; they are relevant to many Geant4 applications, where computational speed and the containment of resources invested in simulation production and quality assurance play a critical role.Comment: 4 pages, 4 figures and images, to appear in proceedings of the Nuclear Science Symposium and Medical Imaging Conference 2009, Orland

Técnicas de produção de sementes florestais.

Este trabalho apresenta informações sobre técnicas de seleção, extração, beneficiamento, secagem e armazenamento de sementes florestais, a fim de obter sementes de boa qualidade.bitstream/item/100452/1/Cot205-sementesflorestais.pd

Técnicas de produção de sementes florestais.

Este trabalho apresenta informações sobre técnicas de seleção, extração, beneficiamento, secagem e armazenamento de sementes florestais, a fim de obter sementes de boa ualidade.bitstream/item/24812/1/Cot-205.pd

Physicochemical and microstructural properties of composite edible film obtained by complex coacervation between chitosan and whey protein isolate

The aim of this work was to study the potential application of edible films obtained by complex coacervation promoted by the electrostatic interactions between positively charged chitosan (CH) 3% (w/w) and negatively charged whey protein isolate (WPI) 3% (w/w). Preliminary assays of turbidimetry were made in order to find the optimal CH-to-WPI mass ratio for the complex coacervation. The maximum turbidity was obtained in the CH:WPI mass ratio of 0.1:1 (w/w). The dispersions of CH/WPI (both at 3 % (w/w)), WPI 5 % (w/w) and CH 3% (w/w) were analyzed by Cryo-scanning electron microscopy (Cryo-SEM) and the micrograph of CH/WPI coacervate presented a more compact network structure than dispersions of individual biopolymers. The composite CH/WPI films were prepared, characterized and their performance and physicochemical properties were compared with those of CH or WPI films, in terms of water vapor permeability (WVP), mechanical properties, solubility, sorption isotherms, optical properties, scanning electron microscopy (SEM) imaging, Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Results revealed that the incorporation of small amounts of CH in the matrix of WPI led to form a composite film with higher tensile strength, lower deformation, malleability, flexibility, solubility and WVP in comparison to the mono-component WPI and CH films. The CH incorporation resulted in a decrease in equilibrium moisture content of the CH/WPI film and the Guggenheim-Anderson-de Boer (GAB) model of sorption data indicated isotherms of type II. All the films presented a homogeneous structure, color transparency, which is desired in food applications and packaging technology.This work was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2020 and UID/QUI/50006/2020 units; the work was also supported by BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte 2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Bose-Einstein Condensation Temperature of Homogenous Weakly Interacting Bose Gas in Variational Perturbation Theory Through Six Loops

We compute the shift of the transition temperature for a homogenous weakly interacting Bose gas in leading order in the scattering length a for given particle density n. Using variational perturbation theory through six loops in a classical three-dimensional scalar field theory, we obtain Delta T_c/T_c = 1.25+/-0.13 a n^(1/3), in agreement with recent Monte-Carlo results.Comment: 4 pages; omega' corrected: final result changes slightly to 1.25+/-0.13; references added; several minor change