Proceedings of the EAA Spatial Audio Signal Processing symposium: SASP 2019

International audienc

Optimization of the pump spectral shape in a parametric down conversion process to generate multimode entangled states.

Quantum optics has been, from its beginning, a driving force both for the exploration of fundamental limits of the quantum world and for conceiving seminal ideas and applications of the so-called quantum technologies. The last 20 years have seen a rapid development of ideas and proof-of-principle experiments involving the fields of quantum communication, quantum computation, quantum metrology and quantum simulation. The so called continuous variable (CV) approach to quantum optics, which uses many photon in collective states, and continuous observables like the quadratures of the electric field to encode information, has many interesting properties, especially from a communications perspective. It is inherently broadband and compatible with standard telecom infrastructures. Moreover, in CV, entanglement, one of the fundamental resource of quantum optics, can be generated deterministically. One of the main challenges for all quantum information technologies is scalability, being able to generate and manipulate a large number of quantum resources to achieve practical tasks efficiently. One approach to solve the issue of scalability is to use highly multimode quantum states. The quantum description of the electromagnetic field associate each photon (particle of light) with a mode (way for light to propagate). In a mutlimodal approach, we look at the quantum state bases and optical modes bases conjointly and tailor quantum fields not only in given modes, but also optimize the spatio-temporal shapes of the modes in which the state is defined. This opens wide perspectives for treating complex quantum states. In particular, using ultra-fast pulses of light which contain many temporal/spectral modes, we are able to generate large and complex entangled states of light using simple resources. In this thesis, we used an optical parametric oscillator pumped synchronously (SPOPO) with a frequency comb to generate multimode squeezed vacuum states which can be used to form cluster states: a large collection of modes (the nodes) entangled to each other in a certain way. These state are the basic resource for Measurement Based Quantum Computation (MBQC). This set-up has the advantage to generate entanglement in many mode with a single device. It is also highly tunable. Indeed, by tuning the spectrum of the OPO pump with a pulse shaper, one can tailor the properties of the generated quantum state. In this work, we focus on the optimization of the pump spectral shape to generate specific states. Using simulations based on Machine Learning Algorithms (MLA), we find optimal pump profile for typical target states. We then implement those shapes on the experimental set-up and measure the resulting states using multipixel homodyne detection. We also study intra-cavity dispersion effects. Dispersion inside the SPOPO cavity is indeed one of the main factor that limits the number of entangled modes in the generated quantum states. A systematic study of dispersion effects is therefore necessary to model the SPOPO output accurately. This works paves the way toward a fully tunable device that can be optimized in real time to generate specific quantum resources tailored for specific tasks

The design of 'possible worlds' as a contribution to the unfinished project of modernity: development of a reference architecture to support the decision-making processes of community-driven sustainable human development initiatives

This dissertation’s central ambitions are to point out and illustrate how design-oriented information systems research (ISR) can be utilized for critical and emancipatory (C&E) purposes as well as—although to a lesser extent—to offer a considerably different perspective on how ISR can contribute to the sustainable development (SD) research agenda. Research programs intending to remove entrenched inequalities by changing the status quo exhibit a C&E orientation. A design-oriented methodology tends to be predestinated as underpinning for such endeavors because of its explicitly stated aim of change. The omnipresent SD discussion, at least in its original conceptualization, is one of the most prominent areas where design-oriented research programs with C&E features are urgently needed. In particular, design science research in information systems (DSRIS), the design-oriented research program in ISR, is considered to be a vital ingredient: the design of appropriate technical systems is gaining in importance, because the complexity and dynamics of SD issues exceed human problem-solving capabilities. However, SD concerns cannot be addressed by isolated technical artifacts; technical systems have to be aligned with the social systems in which they are embedded. This broader endeavor is called the design of socio-technical systems. In comparison to research under this heading, DSRIS rarely strives for C&E goals. This curious situation can be traced back to the methodological suggestions given in the hope that they bridge the ‘relevance-rigor gap’: relevant research has to be carried out in response to problems articulated in practice and results have to be rigorously evaluated in practical settings to demonstrate their efficacy to solve the explicated issues. Besides the inherent challenges of both these prescriptions, from the stance of C&E research, it seems implausible that powerful actors would grant access to a setting and support projects that challenge their positions. Hence, the postulated aim of change is merely an euphemism for endeavors that reinforce and solidify the status quo—they, due to the lack of empowering potential, can solely further what Habermas termed the ‘colonization of the lifeworld’. The method for the design of ‘possible worlds’ proposed in the present inquiry not only helps to overcome this limitation, but it simultaneously integrates DSRIS more clearly with the overarching undertaking of devising socio-technical systems. Against this background, a designed `possible world’, seen from an explicated value position, is a more desirable, theoretically possible alternative to factual existing contexts in a particular domain. It functions as ‘crash barrier’ for the design of social systems and it can at the same time be leveraged as domain model from which it is possible to elicit requirements for the construction of a reference architecture that describes technical systems backing the processes of and within the ‘possible world’. However, in addition to the method’s development, the Ph.D. dissertation also illustrates the former’s application by designing a reference architecture for systems that support the decision-making processes of community-driven sustainable human development initiatives; one at least theoretically possible concretization of SD. As such, the inquiry makes three research contributions: its primary focus is a constructive extension of the disciplinary body of knowledge through the methodical guidance for C&E DSRIS; however, the reflection of SD as part of the exemplary application is also a critique of the way SD issues are currently tackled and of how they are integrated into the ISR canon. To realize these aims the study proceeds as follows: based on a critical reflection of the philosophical underpinnings of DSRIS, it explicates different routes to bridge the relevance-rigor gap. One of these avenues then serves as starting point for the construction of a method that specifically addresses the peculiarities of C&E DSRIS. The core derivation from the traditional conceptualization of design-oriented ISR lies within the sketch of a desirable, hypothetical alternative of factually existing social systems, which, through the contrasting with the latter, allows to carve out intervention entry points, i.e., aspects in which the ‘factual world’ has to change to become more like the ‘possible world’. To justify the claim that this transition, manifesting itself in the determined intervention entry points, is at least theoretically possible and not utopian, the ‘realist synthesis’ as a technique for the gathering of justificatory evidence from the existing body of knowledge is presented. Rooting endeavors of DSRIS in the scientific knowledge base is an important move to free them from being confined to those problems that are articulated by powerful gatekeepers in practical settings. However, for the design of ‘possible worlds’ to bear fruit in ISR, this step needs to be complemented. Therefore, the synthesis is adapted to also permit the extraction of, from the perspective of the underpinning normative stance, suitable ‘draft meanings’, because these progressive (social) structures or organizational options resulting from interventions provide the basis for the design of reference architectures that are aligned with the ‘possible world’. To illustrate this, from an ISR perspective, fundamental usage scenario, the inquiry, based on a devised preliminary reference architecture development approach, carries out the afore-mentioned exemplary application of the method for the design of ‘possible worlds’

Change detection in combination with spatial models and its effectiveness on underwater scenarios

This thesis proposes a novel change detection approach for underwater scenarios and combines it with different especially developed spatial models, this allows accurate and spatially coherent detection of any moving objects with a static camera in arbitrary environments. To deal with the special problems of underwater imaging pre-segmentations based on the optical flow and other special adaptions were added to the change detection algorithm so that it can better handle typical underwater scenarios like a scene crowded by a whole fish swarm

Journal of Telecommunications and Information Technology, nr 3

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NASA Tech Briefs, March 1995

This issue contains articles with a special focus on Computer-Aided design and engineering amd a research report on the Ames Research Center. Other subjects in this issue are: Electronic Components and Circuits, Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Manufacturing/Fabrication, Mathematics and Information Sciences and Life Science

Next generation control of transport networks

It is widely understood by telecom operators and industry analysts that bandwidth demand is increasing dramatically, year on year, with typical growth figures of 50% for Internet-based traffic [5]. This trend means that the consumers will have both a wide variety of devices attaching to their networks and a range of high bandwidth service requirements. The corresponding impact is the effect on the traffic engineered network (often referred to as the “transport network”) to ensure that the current rate of growth of network traffic is supported and meets predicted future demands. As traffic demands increase and newer services continuously arise, novel network elements are needed to provide more flexibility, scalability, resilience, and adaptability to today’s transport network. The transport network provides transparent traffic engineered communication of user, application, and device traffic between attached clients (software and hardware) and establishing and maintaining point-to-point or point-to-multipoint connections. The research documented in this thesis was based on three initial research questions posed while performing research at British Telecom research labs and investigating control of transport networks of future transport networks: 1. How can we meet Internet bandwidth growth yet minimise network costs? 2. Which enabling network technologies might be leveraged to control network layers and functions cooperatively, instead of separated network layer and technology control? 3. Is it possible to utilise both centralised and distributed control mechanisms for automation and traffic optimisation? This thesis aims to provide the classification, motivation, invention, and evolution of a next generation control framework for transport networks, and special consideration of delivering broadcast video traffic to UK subscribers. The document outlines pertinent telecoms technology and current art, how requirements I gathered, and research I conducted, and by which the transport control framework functional components are identified and selected, and by which method the architecture was implemented and applied to key research projects requiring next generation control capabilities, both at British Telecom and the wider research community. Finally, in the closing chapters, the thesis outlines the next steps for ongoing research and development of the transport network framework and key areas for further study

A comparison of the CAR and DAGAR spatial random effects models with an application to diabetics rate estimation in Belgium

When hierarchically modelling an epidemiological phenomenon on a finite collection of sites in space, one must always take a latent spatial effect into account in order to capture the correlation structure that links the phenomenon to the territory. In this work, we compare two autoregressive spatial models that can be used for this purpose: the classical CAR model and the more recent DAGAR model. Differently from the former, the latter has a desirable property: its ρ parameter can be naturally interpreted as the average neighbor pair correlation and, in addition, this parameter can be directly estimated when the effect is modelled using a DAGAR rather than a CAR structure. As an application, we model the diabetics rate in Belgium in 2014 and show the adequacy of these models in predicting the response variable when no covariates are available

A Statistical Approach to the Alignment of fMRI Data

Multi-subject functional Magnetic Resonance Image studies are critical. The anatomical and functional structure varies across subjects, so the image alignment is necessary. We define a probabilistic model to describe functional alignment. Imposing a prior distribution, as the matrix Fisher Von Mises distribution, of the orthogonal transformation parameter, the anatomical information is embedded in the estimation of the parameters, i.e., penalizing the combination of spatially distant voxels. Real applications show an improvement in the classification and interpretability of the results compared to various functional alignment methods