1,721,027 research outputs found
Optical read-out devices based on quantum dots with intrinsic bias
No full textWe study few-particle interactions in a coupled quantum dot system by the use of a semi-analytical model we designed. The model allows for very accurate results and a substantial speed up of calculations. We apply our analysis to the design of a single-electron read-out device based on conditional excitonic dynamics driven by trains of multicolour laser pulses
Field-induced Coulomb coupling in semiconductor macroatoms: Application to "single-electron" quantum devices
Get PDFAn original approach for the control of exciton-exciton Coulomb coupling in semiconductor macroatoms/molecules is proposed. We show that by applying properly tailored external fields, we can induce—or significantly reinforce—excitonic dipoles, which in turn allows one to control and magnify intra- as well as interdot few-exciton effects. Such a dipole-dipole interaction mechanism will be accounted for within a simple analytical model, which is found to be in good agreement with fully three-dimensional calculations. The proposed approach may play an important role for the design and realization of fully optical quantum gates as well as ultrafast optical switches
Tailoring exciton-exciton Coulomb coupling in semiconductor macroatoms using an external electric field
No full textWe present a novel approach for the control of exciton-exciton Coulomb coupling in semiconductor macroatoms/molecules. We exploit electron-hole charge separations induced by the presence of a static external electric field: in this way excitonic dipoles are significantly reinforced. This, in turn, allows us to control and magnify intra- as well as interdot few-exciton effects connected to dipole-dipole coupling. This mechanism will be accounted for within a simple analytical model, which is found to be in good agreement with fully three-dimensional calculations. The proposed approach allows to control and tune exciton-exciton Coulomb coupling, a key quantity for the design and realization of novel single-electron/exciton devices
All-optical single-electron read-out devices based on GaN quantum dots
Get PDFWe study few-particle interactions in GaN-coupled quantum dots and discuss how the built-in field characteristic of these structures strongly reinforce dipole–dipole and dipole–monopole interactions. We introduce a semi-analytical model that allows for a rapid and easy estimate of the magnitude of few-particle interactions and whose predictions are closer than 10% to "exact" results. We apply our study to the design of an all-optical read-out device that exploits long-range dipole–monopole interactions and may be also used to monitor the charge status of a quantum dot system
Intrinsic electric field effects on few-particle interactions in coupled GaN quantum dots
Get PDFWe study the multiexciton optical spectrum of vertically coupled GaN/AlN quantum dots with a realistic
three-dimensional direct-diagonalization approach for the description of few-particle Coulomb-correlated states. We present a detailed analysis of the fundamental properties of few-particle/ exciton interactions peculiar of nitride materials. The giant intrinsic electric fields and the high electron/ hole effective masses give rise to different effects compared to GaAs-based quantum dots: intrinsic exciton-exciton coupling, non molecular character of coupled dot exciton wave function, strong dependence of the oscillator strength on the dot height,
large ground-state energy shift for dots separated by different barriers. Some of these effects make GaN/AlN quantum dots interesting candidates in quantum information processing
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Ultrafast Quantum Information Processing in Nanostructured Semiconductors
No full textWe shall review two implementation proposals for quantum information processing based on charge degrees of freedom in semiconductor nanostructures. An all-optical implementation scheme using semiconductor macroatoms/molecules will be discussed. The computational degrees of freedom in this proposal are interband optical transitions driven by ultrafast sequences of multicolor laser-pulse trains. The conditional dynamics necessary for universal quantum computation is provided by exciton-exciton coupling between different quantum dots in an array. We shall also discuss an alternative scheme based on transport of ballistic electrons in coupled semiconductor quantum wires. In the framework of such implementation strategy, we shall finally discuss a potential simple way for testing violation of Bell's inequality in a condensed-matter setting
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