Quantum-based security in optical fibre networks

Electronic communication is used everyday for a number of different applications. Some of the information transferred during these communications can be private requiring encryption and authentication protocols to keep this information secure. Although there are protocols today which provide some security, they are not necessarily unconditionally secure. Quantum based protocols on the other hand, can provide unconditionally secure protocols for encryption and authentication. Prior to this Thesis, only one experimental realisation of quantum digital signatures had been demonstrated. This used a lossy photonic device along with a quantum memory allowing two parties to test whether they were sent the same signature by a single sender, and also store the quantum states for measurement later. This restricted the demonstration to distances of only a few metres, and was tested with a primitive approximation of a quantum memory rather than an actual one. This Thesis presents an experimental realisation of a quantum digital signature protocol which removes the reliance on quantum memory at the receivers, making a major step towards practicality. By removing the quantum memory, it was also possible to perform the swap and comparison mechanism in a more efficient manner resulting in an experimental realisation of quantum digital signatures over 2 kilometres of optical fibre. Quantum communication protocols can be unconditionally secure, however the transmission distance is limited by loss in quantum channels. To overcome this loss in conventional channels an optical amplifier is used, however the added noise from these would swamp the quantum signal if directly used in quantum communications. This Thesis looked into probabilistic quantum amplification, with an experimental realisation of the state comparison amplifier, based on linear optical components and single-photon detectors. The state comparison amplifier operated by using the wellestablished techniques of optical coherent state comparison and weak subtraction to post-select the output and provide non-deterministic amplification with increased fidelity at a high repetition rate. The success rates of this amplifier were found to be orders of magnitude greater than other state of the art quantum amplifiers, due to its lack of requirement for complex quantum resources, such as single or entangled photon sources, and photon number resolving detectors

Attributes and weights in health care priority setting: a systematic review of what counts and to what extent

In most societies resources are insufficient to provide everyone with all the health care they want. In practice, this means that some people are given priority over others. On what basis should priority be given? In this paper we are interested in the general public's views on this question. We set out to synthesis what the literature has found as a whole regarding which attributes or factors the general public think should count in priority setting and what weight they should receive. A systematic review was undertaken (in August 2014) to address these questions based on empirical studies that elicited stated preferences from the general public. Sixty four studies, applying eight methods, spanning five continents met the inclusion criteria. Discrete Choice Experiment (DCE) and Person Trade-off (PTO) were the most popular standard methods for preference elicitation, but only 34% of all studies calculated distributional weights, mainly using PTO. While there is heterogeneity, results suggest the young are favoured over the old, the more severely ill are favoured over the less severely ill, and people with self-induced illness or high socioeconomic status tend to receive lower priority. In those studies that considered health gain, larger gain is universally preferred, but at a diminishing rate. Evidence from the small number of studies that explored preferences over different components of health gain suggests life extension is favoured over quality of life enhancement; however this may be reversed at the end of life. The majority of studies that investigated end of life care found weak/no support for providing a premium for such care. The review highlights considerable heterogeneity in both methods and results. Further methodological work is needed to achieve the goal of deriving robust distributional weights for use in health care priority setting.12 page(s

Toward a Theory of Business

What is the purpose of business? While most agree that business minimally involves the creation of value, a blurred double image of value haunts our discussion of purpose. The image of what counts as value for a single firm is laid atop an image of what counts as value for business in general. These two images cannot match. Indeed, the resulting conceptual blurriness is a classic example of a composition fallacy. We should never mistake the properties of a part for the properties of the whole. A theory of the firm is ill equipped to handle the many expectations we hold for business practice. As such, we seek to establish the beginnings of a theory of business, one that is both empirical and normative. Offering four central propositions about the purpose, accountability, control and success of business, we close with a consideration of several important theoretical issues and practical opportunities that await us in the years ahead

Computing Perelman's nu-functional

This is a short note in which we show how to calculate the value of Perelman's nu-functional for a variety of metrics. In particular we complete the calculation of values for the known 4-dimensional Einstein and shrinking Ricci soliton metrics.Comment: 9 pages, v2 has new title and slight change of styl

General View of the Agriculture of the County of Northampton, with Observations on the Means of its Improvement. Drawn up for the Consideration of the Board of Agriculture and Internal Improvement, To Which is added an Appendix, containing a Comparison between the English and the Scotch System of Husbandry, as Practised in the Counties of Northampton and Perth

Glosario. -- Northamptonshire. -- Pertenece a la colección Varia 1700-1799 del Salamanca Corpus. -- James Donaldson, fl. 1794. -- General View of the Agriculture of the County of Northampton, with Observations on the Means of its Improvement. Drawn up for the Consideration of the Board of Agriculture and Internal Improvement, To Which is added an Appendix, containing a Comparison between the English and the Scotch System of Husbandry, as Practised in the Counties of Northampton and Perth. -- 1794.[ES]Tratado de agricultura que contiene algo de vocabulario de Northamptonshire. [EN]Agricultural survey which contains some instances of Northamptonshire lexis

Identifying early predictors of instability in CHO cell lines using the Berkley Lights Beacon® Optofluidic System

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