An atomic Hong-Ou-Mandel experiment

The celebrated Hong, Ou and Mandel (HOM) effect is one of the simplest illustrations of two-particle interference, and is unique to the quantum realm. In the original experiment, two photons arriving simultaneously in the input channels of a beam-splitter were observed to always emerge together in one of the output channels. Here, we report on the realisation of a closely analogous experiment with atoms instead of photons. This opens the prospect of testing Bell's inequalities involving mechanical observables of massive particles, such as momentum, using methods inspired by quantum optics, with an eye on theories of the quantum-to-classical transition. Our work also demonstrates a new way to produce and benchmark twin-atom pairs that may be of interest for quantum information processing and quantum simulation

Assimetria de informação e preços diários de ações no Brasil

This paper has the goal of analyzing the association between asymmetric information, measured by Corwin-Schultz bid ask spread estimator, and stock prices in the Brazilian stock market. Daily data from 64 corporations over a period of 10 years were examined using the Johansen-Fisher panel cointegration technique in order to assess the validity of asymmetric information measurements in shorter periods than in previous studies. The results indicate that asymmetric information anticipates stock prices over a period of up to two days in a theoretically consistent way. Future research may control the results via traditional finance variables.Este trabajo tuvo como objetivo analizar la asociación entre información asimétrica, medida a través del estimador Corwin-Schultz, y las cotizaciones bursátiles en el mercado de valores brasileño. Los datos diarios de 64 empresas, en un período de 10 diez años, se examinaron utilizando la técnica de cointegración de panel de Johansen-Fisher para evaluar la validez de una medida de información asimétrica en períodos más cortos que los estudios anteriores. Los resultados indican que la información asimétrica anticipa los precios de las acciones en un período de hasta dos días, de una manera teóricamente consistente. Las investigaciones futuras deberían controlar los resultados mediante variables financieras tradicionales.Este trabalho tem como objetivo analisar a associação entre informação assimétrica, medida pelo estimador Corwin-Schultz, e cotizações bursáteis no mercado brasileiro de ações. Foram analisados dados diários de 64 empresas, durante um perídodo de 10 anos, pela técnica de cointegração para dados em painel de Johansen-Fisher, para avaliar a validade de uma medida de informação assimétrica em períodos inferiores aos de estudos anteriores. Os resultados indicam que a informação assimétrica antecipa o preço das ações em um período de até 2 dias, de maneira teoricamente consistente. Pesquisas futuras deveriam controlar os resultados mediante variáveis financeiras tradicionais

Residual Policy Learning for Vehicle Control of Autonomous Racing Cars

The development of vehicle controllers for autonomous racing is challenging because racing cars operate at their physical driving limit. Prompted by the demand for improved performance, autonomous racing research has seen the proliferation of machine learning-based controllers. While these approaches show competitive performance, their practical applicability is often limited. Residual policy learning promises to mitigate this by combining classical controllers with learned residual controllers. The critical advantage of residual controllers is their high adaptability parallel to the classical controller's stable behavior. We propose a residual vehicle controller for autonomous racing cars that learns to amend a classical controller for the path-following of racing lines. In an extensive study, performance gains of our approach are evaluated for a simulated car of the F1TENTH autonomous racing series. The evaluation for twelve replicated real-world racetracks shows that the residual controller reduces lap times by an average of 4.55 % compared to a classical controller and zero-shot generalizes to new racetracks.Comment: Submitted to IEEE Intelligent Vehicles Symposium 202

Investigation of the Uptake, Metabolism and Delivery of Polyunsaturated Fatty Acids in the Developing Avian Embryo

The avian embryo exhibits a range of unique features which favour its suitability as a model for investigating polyunsaturated fatty acid (PUFA) metabolism and transport. Recent evidence has shown that metabolic remodelling of yolk fatty acid moieties occur in the yolk complex, especially the transfer of docosahexaenoic acid (DHA) from phospholipid (PL) fraction in the yolk to triacylglycerol (TG) fraction in the blood. Moreover a preferential disappearance of yolk DHA associated with the phospholipid fraction specifically phosphatidylethanolamine, had been described at around day 12. A phospholipase A2 was found to be involved in this process coincident with an increase of DHA within the free fatty acid fraction in the yolk. Fatty acid metabolism in the yolk sac membrane during embryonic development has been studied. The activities of key regulatory enzymes of acyl glycerolipid synthesis and oxidation were measured; carnitine palmitoyltransferase I, monoacylglycerol acyltransferase, glycerolphosphate acyltransferase and diacylglycerol acyltransferase. Maximal CPT I activity was found at day 12 and significantly declined to day 18. The MGAT activity remained constant throughout development suggesting that this pathway of glycerolipid biosynthesis may provide a mechanism to selectively retain essential PUFAs during a period of intense fatty acid oxidation. The measured activity of microsomal GPAT was noticeably lower compared to MGAT, with peak activity at day 12. The presence of DGAT activity completes the TG synthetic pathway which is released into the embryonic blood as part of very low density lipoproteins (VLDL). Characterisation and analysis of lipoprotein lipid in the blood at day 14 and day 22 extended the knowledge regarding the delivery system of DHA in the avian embryo. The VLDL TG was hydrolysed by lipoprotein lipase with the accompanying uptake of fatty acids into the adipose tissue. Hydrolysis of TG containing DHA by LPL appeared to be less active towards other TG species resulting in an enrichment of DHA in the TG of resulting lipoproteins which would be cleared by the liver. The results suggest that the yolk sac membrane has an important role in the regulation of DHA delivery to the developing embryo. Moreover the supply of DHA to the neural tissues in the developing embryo appears to be coordinated by both the adipose tissue and liver

Stark Effect of Hybrid Charge Transfer States at Planar ZnO/Organic Interfaces

We investigate the bias-dependence of the hybrid charge transfer state emission at planar heterojunctions between the metal oxide acceptor ZnO and three donor molecules. The electroluminescence peak energy linearly increases with the applied bias, saturating at high fields. Variation of the organic layer thickness and deliberate change of the ZnO conductivity through controlled photo-doping allow us to confirm that this bias-induced spectral shifts relate to the internal electric field in the organic layer rather than the filling of states at the hybrid interface. We show that existing continuum models overestimate the hole delocalization and propose a simple electrostatic model in which the linear and quadratic Stark effects are explained by the electrostatic interaction of a strongly polarizable molecular cation with its mirror image

Optimal and Variational Multi-Parameter Quantum Metrology and Vector Field Sensing

We study multi-parameter sensing of 2D and 3D vector fields within the Bayesian framework for $SU(2)$ quantum interferometry. We establish a method to determine the optimal quantum sensor, which establishes the fundamental limit on the precision of simultaneously estimating multiple parameters with an $N$-atom sensor. Keeping current experimental platforms in mind, we present sensors that have limited entanglement capabilities, and yet, significantly outperform sensors that operate without entanglement and approach the optimal quantum sensor in terms of performance. Furthermore, we show how these sensors can be implemented on current programmable quantum sensors with variational quantum circuits by minimizing a metrological cost function. The resulting circuits prepare tailored entangled states and perform measurements in an appropriate entangled basis to realize the best possible quantum sensor given the native entangling resources available on a given sensor platform. Notable examples include a 2D and 3D quantum ``compass'' and a 2D sensor that provides a scalable improvement over unentangled sensors. Our results on optimal and variational multi-parameter quantum metrology are useful for advancing precision measurements in fundamental science and ensuring the stability of quantum computers, which can be achieved through the incorporation of optimal quantum sensors in a quantum feedback loop.Comment: 20 pages, 8 figure

Determinants of Soil Conservation Technologies Among Small-Scale Farmers in Tanzania; Evidence from National Panel Survey

The adoption of Soil Conservation Technologies (SCTs) in Tanzania is very low compared to other countries in Africa with related situation. Interventions were taken by introducing soil conservation practices. However, the adoption of these practices is far below the expectation. The objective of this study was to examine the determinants ofSCTs among maize small-scale farmers in Tanzania. Secondary data from the National Panel Survey was used in this study. A binary probit regression model was employed to analyse the data. The analysis results showed that access to extension services and training as well as plot value were positively correlated at significantly level with the adoption of the introduced soil and water conservation practices. On the other hand, soil steepness influenced the adoption of soil conservation practices negatively. The finding depicts that the identified physical, socioeconomic, and institutional factors influence the adoption of SCTs so; concerned bodies should consider these influential factors to enhance farmers’ adoption of soil conservation practices and promote agricultural productivity and environmental quality

Magnetoconductance, Quantum Hall Effect, and Coulomb Blockade in Topological Insulator Nanocones

Magnetotransport through cylindrical topological insulator (TI) nanowires is governed by the interplay between quantum confinement and geometric (Aharonov-Bohm and Berry) phases. Here, we argue that the much broader class of TI nanowires with varying radius—for which a homogeneous coaxial magnetic field induces a varying Aharonov-Bohm flux that gives rise to a nontrivial masslike potential along the wire—is accessible by studying its simplest member, a TI nanocone. Such nanocones allow us to observe intriguing mesoscopic transport phenomena: While the conductance in a perpendicular magnetic field is quantized due to higher-order topological hinge states, it shows resonant transmission through Dirac Landau levels in a coaxial magnetic field. Furthermore, it may act as a quantum magnetic bottle, confining surface Dirac electrons and leading to a largely interaction-dominated regime of Coulomb blockade type. We show numerically that the above-mentioned effects occur for experimentally accessible values of system size and magnetic field, suggesting that TI nanocone junctions may serve as building blocks for Dirac electron optics setups