183,079 research outputs found

    Quantum enigma machines and the locking capacity of a quantum channel

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    The locking effect is a phenomenon which is unique to quantum information theory and represents one of the strongest separations between the classical and quantum theories of information. The Fawzi-Hayden-Sen (FHS) locking protocol harnesses this effect in a cryptographic context, whereby one party can encode n bits into n qubits while using only a constant-size secret key. The encoded message is then secure against any measurement that an eavesdropper could perform in an attempt to recover the message, but the protocol does not necessarily meet the composability requirements needed in quantum key distribution applications. In any case, the locking effect represents an extreme violation of Shannon's classical theorem, which states that information-theoretic security holds in the classical case if and only if the secret key is the same size as the message. Given this intriguing phenomenon, it is of practical interest to study the effect in the presence of noise, which can occur in the systems of both the legitimate receiver and the eavesdropper. This paper formally defines the locking capacity of a quantum channel as the maximum amount of locked information that can be reliably transmitted to a legitimate receiver by exploiting many independent uses of a quantum channel and an amount of secret key sublinear in the number of channel uses. We provide general operational bounds on the locking capacity in terms of other well-known capacities from quantum Shannon theory. We also study the important case of bosonic channels, finding limitations on these channels' locking capacity when coherent-state encodings are employed and particular locking protocols for these channels that might be physically implementable.Comment: 37 page

    Mutual Unbiasedness in Coarse-grained Continuous Variables

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    The notion of mutual unbiasedness for coarse-grained measurements of quantum continuous variable systems is considered. It is shown that while the procedure of "standard" coarse graining breaks the mutual unbiasedness between conjugate variables, this desired feature can be theoretically established and experimentally observed in periodic coarse graining. We illustrate our results in an optics experiment implementing Fraunhofer diffraction through a periodic diffraction grating, finding excellent agreement with the derived theory. Our results are an important step in developing a formal connection between discrete and continuous variable quantum mechanics.Comment: 5 pages, 3 figures + Supplemental Material (1 page) v2: Introduction expanded, minor typos correcte

    Mutual Unbiasedness in Coarse-grained Continuous Variables

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    The notion of mutual unbiasedness for coarse-grained measurements of quantum continuous variable systems is considered. It is shown that while the procedure of "standard" coarse graining breaks the mutual unbiasedness between conjugate variables, this desired feature can be theoretically established and experimentally observed in periodic coarse graining. We illustrate our results in an optics experiment implementing Fraunhofer diffraction through a periodic diffraction grating, finding excellent agreement with the derived theory. Our results are an important step in developing a formal connection between discrete and continuous variable quantum mechanics.Comment: 5 pages, 3 figures + Supplemental Material (1 page) v2: Introduction expanded, minor typos correcte

    Examining client perceptions of partnership quality and its dimensions in an IT outsourcing relationship

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    This paper reports on an empirical study of the multidimensionality of partnership quality in IT outsourcing arrangements and the relationships between these dimensions of partnership quality. A two-phase national survey was conducted to collect empirical data to confirm the dimensions of partnership quality in an IT outsourcing arrangement from the client organisation perspective and to identify the significant relationships between these dimensions using a second generation multivariate analysis technique—partial least squares (PLS). The findings from results of the data analyses show that inter-organisational trust, shared business understanding and to a lesser extent, functional and dysfunctional conflict between the client organisation and the outsourcing vendor in an IT outsourcing relationship are the key determinants of partnership quality. The key outcome variable for high partnership quality between the client organisation and the outsourcing vendor in an IT outsourcing relationship is mutual beneficial sharing of risks and benefits. Commitment in an IT outsourcing relationship is confirmed as a multidimensional construct of behaviour commitment and temporal/continuance commitment and was found to be influenced by the other dimensions of partnership quality. The key findings of this study provide support for the notion that trust and shared business understanding are key drivers in the IT outsourcing partnership style relationship ensuring that the sharing of risks and benefits are realised and conflict is minimised leading to a high quality and ultimately successful partnership between the client organisation and the outsourcing vendor. Furthermore our findings indicate that behavioural commitment to the contractual obligations of an IT outsourcing relationship sustains an ongoing temporal commitment to the partnership between the client organisation and the outsourcing vendor

    Transformational Leadership and Knowledge Management: Analysing the Knowledge Management Models

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    The purpose of the present study is to investigate the mutual relationship between transformational leadership and knowledge management as well the potential effects of a transformational leader on his or her followers. In this paper, we review the role of transformational leadership in effective knowledge management and establish the emerging role of transformational leadership, as an ideal leadership style in building knowledge-based companies to achieve a higher degree of competitive advantage. The findings in this article are based upon previous empirical studies that illustrate the formulation of several propositions that contribute to the knowledge management processes. Our findings are based upon possible scenarios that impact transformational leadership and knowledge management using grounded theoretical research. Research limitations are twofold. One limitation is found in the prior literature indicating that past studies have posited that companies might lack the required capabilities or decide to decline from interacting with other companies (Caldwell & Ancona 1988), or even distrust sharing their knowledge (Kraut & Streeter 1995). And, second, our contribution to the literature lies in presenting a link between knowledge management and transformational leadership that incorporates the knowledge management processes that may impact the effectiveness of transformational leaders to enhance their capabilities to effectively play their roles within companies. In addition, managerial applications that may support knowledge management processes are proposed further research is necessary to finalise conclusions. The original value of this research provides an impetus of mutual interaction of knowledge management and transformational leadership

    Impact of urban geometry on indoor air temperature and cooling energy consumption in traditional and formal urban environments

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    The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the URI link.This study explores the effect of outdoor microclimatic environment on indoor conditions in a tropical warm-humid climate. An indoor air temperature and building energy performance analysis is carried out for the real case-study areas to examine the impact of urban geometry on building indoor conditions. The study incorporates microclimatic data from CFD, micro-climatic tool ENVI-met into building energy performance analysis using IES-VE. Findings reveal that diversity in urban geometry in deep urban canyons is helpful in reducing the indoor air temperature and cooling load. On average, cooling load in model rooms in the formal area is 21% higher for 1st floors (40% for top floors) compared to the corresponding rooms in the traditional area. In terms of solar gains, the difference was 30% for the 1st floors and 91% for the top floors, with rooms in the formal area having the higher ranges. Furthermore, the room air temperature in the traditional area was found to be 0.6-1.6 Deg C lower than those in the formal area

    Heisenberg's uncertainty principle

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    Heisenberg's uncertainty principle is usually taken to express a limitation of operational possibilities imposed by quantum mechanics. Here we demonstrate that the full content of this principle also includes its positive role as a condition ensuring that mutually exclusive experimental options can be reconciled if an appropriate trade-off is accepted. The uncertainty principle is shown to appear in three manifestations, in the form of uncertainty relations: for the widths of the position and momentum distributions in any quantum state; for the inaccuracies of any joint measurement of these quantities; and for the inaccuracy of a measurement of one of the quantities and the ensuing disturbance in the distribution of the other quantity. Whilst conceptually distinct, these three kinds of uncertainty relations are shown to be closely related formally. Finally, we survey models and experimental implementations of joint measurements of position and momentum and comment briefly on the status of experimental tests of the uncertainty principle. (c) 2007 Elsevier B.V. All rights reserved
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