Emergence of spatial spin-wave correlations in a cold atomic gas

Rydberg spin waves are optically excited in a quasi-one-dimensional atomic sample of Rb atoms. Pair-wise spin-wave correlations are observed by a spatially selective transfer of the quantum state onto a light field and photoelectric correlation measurements of the light. The correlations are interpreted in terms of the dephasing of multiply-excited spin waves by long-range Rydberg interactions

Dephasing dynamics of Rydberg atom spin waves

A theory of Rydberg atom interactions is used to derive analytical forms for the spin wave pair correlation function in laser-excited cold-atom vapors. This function controls the quantum statistics of light emission from dense, inhomogeneous clouds of cold atoms of various spatial dimensionalities. The results yield distinctive scaling behaviors on the microsecond timescale, including generalized exponential decay. A detailed comparison is presented with a recent experiment on a cigar-shaped atomic ensemble [Y. Dudin and A. Kuzmich, Science 336, 887 (2012)], in which Rb atoms are excited to a set of Rydberg levels.Comment: 4 pages, Supplemental Material in Appendix, 4 figure

Photon Wave-packet Manipulation via Dynamic Electromagnetically Induced Transparency in Multilayer Structures

We present a Maxwell-Bloch description of the dynamics of a light pulse propagating through a spatially inhomogeneous system consisting of alternating layers of EIT media and vacuum. We study the effect of a dynamical modulation of the EIT control field on the shape of the wave packet: interesting effects due to the presence of interfaces with group velocity mismatch are found. An effective description based on a continuity equation is developed. Modulation schemes that can be realized in ultracold atomic samples with standard experimental techniques are proposed and discussed

Energy performance and climate control in mechanically ventilated greenhouses: A dynamic modelling-based assessment and investigation

Controlled environment agriculture in greenhouse is a promising solution for meeting the increasing food demand of world population. The accurate control of the indoor environmental conditions proper of greenhouses enhances high crop productivity but, contemporarily, it entails considerable energy consumption due to the adoption of mechanical systems. This work presents a new modelling approach for estimating the energy consumption for climate control of mechanically ventilated greenhouses. The novelty of the proposed energy model lies in its integrated approach in simulating the greenhouse dynamics, considering the dynamic thermal and hygric behaviour of the building and the dynamic response of the cultivated crops to the variation of the solar radiation. The presented model simulates the operation of the systems and the energy performance, considering also the variable angular speed fans that are a new promising energy-efficient technology for this productive sector. The main outputs of the model are the hourly thermal and electrical energy use for climate control and the main indoor environmental conditions. The presented modelling approach was validated against a dataset acquired in a case study of a new fully mechanically controlled greenhouse during a long-term monitoring campaign. The present work contributes to increase the knowledge about the dynamics and the energy consumption of greenhouses, and it can be a valuable decision support tool for industry, farmers, and researchers to properly address an energy efficiency optimisation in mechanically ventilated greenhouses to reach the overall objective of decreasing the rising energy consumption of the agricultural sector

Observation of coherent many-body Rabi oscillations

A two-level quantum system coherently driven by a resonant electromagnetic field oscillates sinusoidally between the two levels at frequency $\Omega$ which is proportional to the field amplitude [1]. This phenomenon, known as the Rabi oscillation, has been at the heart of atomic, molecular and optical physics since the seminal work of its namesake and coauthors [2]. Notably, Rabi oscillations in isolated single atoms or dilute gases form the basis for metrological applications such as atomic clocks and precision measurements of physical constants [3]. Both inhomogeneous distribution of coupling strength to the field and interactions between individual atoms reduce the visibility of the oscillation and may even suppress it completely. A remarkable transformation takes place in the limit where only a single excitation can be present in the sample due to either initial conditions or atomic interactions: there arises a collective, many-body Rabi oscillation at a frequency $N^0.5\Omega$ involving all N >> 1 atoms in the sample [4]. This is true even for inhomogeneous atom-field coupling distributions, where single-atom Rabi oscillations may be invisible. When one of the two levels is a strongly interacting Rydberg level, many-body Rabi oscillations emerge as a consequence of the Rydberg excitation blockade. Lukin and coauthors outlined an approach to quantum information processing based on this effect [5]. Here we report initial observations of coherent many-body Rabi oscillations between the ground level and a Rydberg level using several hundred cold rubidium atoms. The strongly pronounced oscillations indicate a nearly complete excitation blockade of the entire mesoscopic ensemble by a single excited atom. The results pave the way towards quantum computation and simulation using ensembles of atoms

Bright and dark excitons in an atom--pair filled optical lattice within a cavity

We study electronic excitations of a degenerate gas of atoms trapped in pairs in an optical lattice. Local dipole-dipole interactions produce a long lived antisymmetric and a short lived symmetric superposition of individual atomic excitations as the lowest internal on-site excitations. Due to the much larger dipole moment the symmetric states couple efficiently to neighbouring lattice sites and can be well represented by Frenkel excitons, while the antisymmetric dark states stay localized. Within a cavity only symmetric states couple to cavity photons inducing long range interactions to form polaritons. We calculate their dispersion curves as well as cavity transmission and reflection spectra to observe them. For a lattice with aspherical sites bright and dark states get mixed and their relative excitation energies depend on photon polarizations. The system should allow to study new types of solid state phenomena in atom filled optical lattices

Role of ventricular tachycardia ablation in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by progressive fibro-fatty replacement of the myocardium that represents the substrate for recurrent sustained ventricular tachycardia (VT). These arrhythmias characterize the clinical course of a sizeable proportion of patients and have significant implications for their quality of life and long-term prognosis. Antiarrhythmic drugs are often poorly tolerated and usually provide incomplete control of arrhythmia relapses. Catheter ablation is a potentially effective strategy to treat frequent VT episodes and ICD shocks in ARVC patients. The aims of this review are to discuss the electrophysiological and electroanatomic substrates of ventricular tachycardia in patients with ARVC and to analyze the role of catheter ablation in their management with particular reference to selection of patients, technical issues, potential complications and outcomes

Um referencial de self coaching para apoiar processos de mentorias.

Em 2019 ocorreu o primeiro ciclo do TechStart Agro Digital, tendo sido a experiência de seu planejamento e execução a base para que se identificasse e aplicasse para o ciclo de 2020/2021 algumas adaptações metodológicas, de forma a contemplar maior aproximação entre as startups aceleradas e os mentores técnicos do programa, que são empregados, analistas e pesquisadores da Empresa Brasileira de Pesquisa Agropecuária (Embrapa). Uma maior definição a respeito da carga horária de dedicação ao programa, incluindo-se a carga horária dedicada exclusivamente à realização de sessões de mentoria, sob liderança do mentor, bem como uma melhor preparação dos mentores para que fosse possível a definição antecipada de quais ferramentas adicionais de tecnologia, produto ou mercado, seriam agregados durante o processo de aceleração. O material apresentado neste documento foi desenvolvido como parte do processo de preparação dos mentores da Embrapa para que atuem em programas de aceleração de startups no segundo ciclo do TechStart AgroDigital (TSAD), realizado em 2020 e 2021. Essa parte do processo, corresponde a um treinamento para ampliar autoconhecimento e melhorar os relacionamentos interpessoais. O processo completo, desenvolvido no contexto do projeto Soluções Tecnológicas para Aceleração de Negócios em Agricultura Digital - StarAgro (Código do projeto no IDEARE: 30.21.90.010.00.00), liderado pela Embrapa Agricultura Digital, também foi aplicado a outro programa de inovação da Embrapa, o SoilsPlay da Embrapa Solos, em 2021. Devido à relativa aceitação do treinamento realizado e à sua aplicabilidade no dia a dia, decidiu-se publicá-lo não apenas como apostila de curso, mas em uma linguagem que permita a utilização de partes do material em outros treinamentos ou mesmo como um self coaching pelo seu leitor. Embora o material proposto tenha sido desenvolvido para atendimento às particularidades do Programa TechStart AgroDigital, acredita-se que pequenas modificações sejam possíveis aos interessados em aplicá-los a outros contextos de inovação, com outros grupos de mentores e líderes de iniciativas correlatas da Empresa