346,666 research outputs found
Cluster-based architecture for fault-tolerant quantum computation
We present a detailed description of an architecture for fault-tolerant
quantum computation, which is based on the cluster model of encoded qubits. In
this cluster-based architecture, concatenated computation is implemented in a
quite different way from the usual circuit-based architecture where physical
gates are recursively replaced by logical gates with error-correction gadgets.
Instead, some relevant cluster states, say fundamental clusters, are
recursively constructed through verification and postselection in advance for
the higher-level one-way computation, which namely provides error-precorrection
of gate operations. A suitable code such as the Steane seven-qubit code is
adopted for transversal operations. This concatenated construction of verified
fundamental clusters has a simple transversal structure of logical errors, and
achieves a high noise threshold ~ 3 % for computation by using appropriate
verification procedures. Since the postselection is localized within each
fundamental cluster with the help of deterministic bare controlled-Z gates
without verification, divergence of resources is restrained, which reconciles
postselection with scalability.Comment: 16 pages, 34 figure
Mission Engineering and the CubeSat System Reference Model
SSWG has been investigating the applicability of MBSE for designing CubeSats since 2011.
The first phase developed a SysML model of a CubeSat and applied it to the Radio Aurora Explorer. The second phase included modeling behaviors and the third phase included carrying out trade studies.
The current phase is the development of the CubeSat System Reference Model (CSRM).
The CSRM provides the logical architecture of a CubeSat space and ground system. The CSRM logical components are reused as a starting point for a mission-specific CubeSat logical architecture followed by the development of the physical architecture during CubeSat development. The mission-specific team is free to adopt a different logical architecture and modify the CSRM to accommodate the change
Layered architecture for quantum computing
We develop a layered quantum computer architecture, which is a systematic
framework for tackling the individual challenges of developing a quantum
computer while constructing a cohesive device design. We discuss many of the
prominent techniques for implementing circuit-model quantum computing and
introduce several new methods, with an emphasis on employing surface code
quantum error correction. In doing so, we propose a new quantum computer
architecture based on optical control of quantum dots. The timescales of
physical hardware operations and logical, error-corrected quantum gates differ
by several orders of magnitude. By dividing functionality into layers, we can
design and analyze subsystems independently, demonstrating the value of our
layered architectural approach. Using this concrete hardware platform, we
provide resource analysis for executing fault-tolerant quantum algorithms for
integer factoring and quantum simulation, finding that the quantum dot
architecture we study could solve such problems on the timescale of days.Comment: 27 pages, 20 figure
A Logic-based Approach for Recognizing Textual Entailment Supported by Ontological Background Knowledge
We present the architecture and the evaluation of a new system for
recognizing textual entailment (RTE). In RTE we want to identify automatically
the type of a logical relation between two input texts. In particular, we are
interested in proving the existence of an entailment between them. We conceive
our system as a modular environment allowing for a high-coverage syntactic and
semantic text analysis combined with logical inference. For the syntactic and
semantic analysis we combine a deep semantic analysis with a shallow one
supported by statistical models in order to increase the quality and the
accuracy of results. For RTE we use logical inference of first-order employing
model-theoretic techniques and automated reasoning tools. The inference is
supported with problem-relevant background knowledge extracted automatically
and on demand from external sources like, e.g., WordNet, YAGO, and OpenCyc, or
other, more experimental sources with, e.g., manually defined presupposition
resolutions, or with axiomatized general and common sense knowledge. The
results show that fine-grained and consistent knowledge coming from diverse
sources is a necessary condition determining the correctness and traceability
of results.Comment: 25 pages, 10 figure
An autonomous satellite architecture integrating deliberative reasoning and behavioural intelligence
This paper describes a method for the design of autonomous spacecraft, based upon behavioral approaches to intelligent robotics. First, a number of previous spacecraft automation projects are reviewed. A methodology for the design of autonomous spacecraft is then presented, drawing upon both the European Space Agency technological center (ESTEC) automation and robotics methodology and the subsumption architecture for autonomous robots. A layered competency model for autonomous orbital spacecraft is proposed. A simple example of low level competencies and their interaction is presented in order to illustrate the methodology. Finally, the general principles adopted for the control hardware design of the AUSTRALIS-1 spacecraft are described. This system will provide an orbital experimental platform for spacecraft autonomy studies, supporting the exploration of different logical control models, different computational metaphors within the behavioral control framework, and different mappings from the logical control model to its physical implementation
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Investigating pluralistic data architectures in data warehousing
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonUnderstanding and managing change is a strategic objective for many organisations to successfully compete in a market place; as a result, organisations are leveraging their data asset and implementing data warehouses to gain business intelligence necessary to improve their businesses. Data warehouses are expensive initiatives, one-half to two-thirds of most data warehousing efforts end in failure. In the absence of well-formalised design methodology in the industry and in the context of the debate on data architecture in data warehousing, this thesis examines why multidimensional and relational data models define the data architecture landscape in the industry. The study develops a number of propositions from the literature and empirical data to understand the factors impacting the choice of logical data model in data warehousing. Using a comparative case study method as the mean of collecting empirical data from the case organisations, the research proposes a conceptual model for logical data model adoption. The model provides a framework that guides decision making for adopting a logical data model for a data warehouse. The research conceptual model identifies the characteristics of business requirements and decision pathways for multidimensional and relational data warehouses. The conceptual model adds value by identifying the business requirements which a multidimensional and relational logical data model is empirically applicable
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Asynchronous data retrieval from an object-oriented database
We present an object-oriented semantic database model which, similar to other object-oriented systems, combines the virtues of four concepts: the functional data model, a property inheritance hierarchy, abstract data types and message-driven computation. The main emphasis is on the last of these four concepts. We describe generic procedures that permit queries to be processed in a purely message-driven manner. A database is represented as a network of nodes and directed arcs, in which each node is a logical processing element, capable of communicating with other nodes by exchanging messages. This eliminates the need for shared memory and for centralized control during query processing. Hence, the model is suitable for implementation on a multiprocessor computer architecture, consisting of large numbers of loosely coupled processing elements
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