Using the EQ-5D as a performance measurement tool in the NHS

In a landmark move, the UK Department of Health (DH) is introducing the routine use of Patient Reported Outcome Measures (PROMs) as a means of measuring the performance of health care providers in improving patient health. From April 2009 all patients will be asked to complete both generic (EQ-5D) and condition specific PROMs before and after surgery for four elective procedures; the intention is to extend this to a wide range of other NHS services. The aim of this paper is to report analysis of the EQ-5D data generated from a pilot study commissioned by the DH, and to consider the implications of the results for their use as performance indicators and measures of patient benefit. The EQ-5D has the potential advantage in the context of PROMs of enabling comparisons of performance across services as well as between providers; and in facilitating assessments of the cost effectiveness of NHS services. We present two new methods we have developed for analysing and displaying EQ-5D profile data: a Paretian Classification of Health Change, and a Health Profile Grid. Using these methods, we show that EQ-5D data can readily be used to generate useful insights into differences between providers in improving overall changes in health; results are also suggestive of striking differences in changes in health between surgical procedures. We conclude by noting a number of issues that remain to be addressed in the use of PROMs data as a basis for performance indicators

The distributional effect of the 2008 Pre-Budget Report

The Pre-Budget Report given by the Chancellor on 24th November 2008 contained a number of changes to the tax and benefit system to come into effect at various points over the next three years. This briefing note expands on the information provided at a briefing given by IFS researchers on the day after the Pre-Budget Report1. It gives details of the changes to taxes, benefits and tax credits directly affecting households, and the total distributional impact of measures announced in PBR 2008 together with pre-announced changes, by income and expenditure decile and household type, at three points in time – January 2009, April 2009 and April 2011. It also discusses what PBR 2008 does to our impression of all tax and benefit changes under this Government. Finally, it discusses what PBR 08 did for child poverty in 2010/11 and the likely effects of the income tax changes for those earning more than £100,000 a year

How good must single photon sources and detectors be for efficient linear optical quantum computation?

We present a scheme for linear optical quantum computation (LOQC) which is highly robust to imperfect single photon sources and inefficient detectors. In particular we show that if the product of the detector efficiency with the source efficiency is greater than 2/3, then efficient LOQC is possible. This threshold is many orders of magnitude more relaxed than those which could be inferred by application of standard results in fault tolerance. The result is achieved within the cluster state paradigm for quantum computation.Comment: New version contains an Added Appendi

First Principles LCGO Calculation of the Magneto-optical Properties of Nickel and Iron

We report a first principles, self-consistent, all electron, linear combination of Gaussian orbitals (LCGO) calculation of a comprehensive collection of magneto-optical properties of nickel and iron based on density functional theory. Among the many magneto-optical effects, we have studied the equatorial Kerr effect for absorption in the optical as well as soft X-ray region, where it is called X-ray magnetic linear dichroism (X-MLD). In the optical region the effect is of the order of 2\% while in the X-ray region it is of the order of 1\% for the incident angles considered. In addition, the polar Kerr effect, X-ray magnetic circular dichroism (X-MCD) and total X-ray absorption at the L$_{2,3}$ edges, soft X-ray Faraday effect at the L$_{2,3}$ edges have also been calculated. Our results are in good agreement with experiments and other first principles methods that have been used to calculate some of these properties.Comment: 22 pages RevTex. 8 figures submitted separately as a uuencoded, compressed tar fil

Finding Optimal Flows Efficiently

Among the models of quantum computation, the One-way Quantum Computer is one of the most promising proposals of physical realization, and opens new perspectives for parallelization by taking advantage of quantum entanglement. Since a one-way quantum computation is based on quantum measurement, which is a fundamentally nondeterministic evolution, a sufficient condition of global determinism has been introduced as the existence of a causal flow in a graph that underlies the computation. A O(n^3)-algorithm has been introduced for finding such a causal flow when the numbers of output and input vertices in the graph are equal, otherwise no polynomial time algorithm was known for deciding whether a graph has a causal flow or not. Our main contribution is to introduce a O(n^2)-algorithm for finding a causal flow, if any, whatever the numbers of input and output vertices are. This answers the open question stated by Danos and Kashefi and by de Beaudrap. Moreover, we prove that our algorithm produces an optimal flow (flow of minimal depth.) Whereas the existence of a causal flow is a sufficient condition for determinism, it is not a necessary condition. A weaker version of the causal flow, called gflow (generalized flow) has been introduced and has been proved to be a necessary and sufficient condition for a family of deterministic computations. Moreover the depth of the quantum computation is upper bounded by the depth of the gflow. However, the existence of a polynomial time algorithm that finds a gflow has been stated as an open question. In this paper we answer this positively with a polynomial time algorithm that outputs an optimal gflow of a given graph and thus finds an optimal correction strategy to the nondeterministic evolution due to measurements.Comment: 10 pages, 3 figure

Loss tolerant linear optical quantum memory by measurement-based quantum computing

We give a scheme for loss tolerantly building a linear optical quantum memory which itself is tolerant to qubit loss. We use the encoding recently introduced in Varnava et al 2006 Phys. Rev. Lett. 97 120501, and give a method for efficiently achieving this. The entire approach resides within the 'one-way' model for quantum computing (Raussendorf and Briegel 2001 Phys. Rev. Lett. 86 5188–91; Raussendorf et al 2003 Phys. Rev. A 68 022312). Our results suggest that it is possible to build a loss tolerant quantum memory, such that if the requirement is to keep the data stored over arbitrarily long times then this is possible with only polynomially increasing resources and logarithmically increasing individual photon life-times