The Projection Postulate of Quantum Mechanics on the Lightcone

We discuss an interpretation of the projection postulate that implies collapse of the wavefunction along the lightcone.Comment: 5 pages, LaTex, SJSU/TP-93-1

Aid Volatility, Policy and Development

We build on Bulir and Hamann's analysis of aid volatility (2003, 2005), showing that the conclusions reached depend on the dataset used. Their argument that the poorest countries have the highest volatility appears not to be correct. The impact of volatility on growth is negative overall, but differs between positive and negative volatility. The mix between `responsive´ components of aid, e.g. programme aid, and `proactive´ components, e.g. technical assistance, is important. Finally, we conclude that measures which increase trust between donor and recipient, and reductions in the degree of donor `oligopoly´, reduce aid volatility without obviously reducing its effectiveness

Capital controls re-examined: the case for ‘smart’ controls

The global financial crisis which began in east Asia in 1997 is not over, neither is the inquest into its implications for adjustment policy. In the wake of this crisis, we focus here on the role of capital controls, which formed a much publicised part of the crisis-coping strategy in one country (Malaysia) and, less openly, were also deployed by other crisis-afflicted countries. Evaluation so far has examined different target variables with different estimation methods, generally concentrating on efficiency and stability indicators and ignoring equity measures; it has also typically treated `control´ as a one-zero dummy variable, ignoring the `quality´ of intervention and in particular the extent to which efficiency gains are obtained in exchange for controls. Partly because of these limitations, the literature has reached no consensus on the impact of controls, nor therefore about where they fit within the set of post-crisis defence mechanisms. We propose an approach in which the government plays off short-term political security against long-term economic gain; the more insecure its political footing, the greater the weight it gives to political survival, which is likely to increase the probability of controls being imposed. The modelling of this approach generates a governmental `policy reaction function´ and an impact function for controls, which are estimated by simultaneous panel-data methods across a sample of thirty developing and transitional countries between 1980-2003, using, for the period since 1996, the `new´ IMF dataset which differentiates between controls by type. We find that controls appear to cause increases in income equality, and are significantly associated with political insecurity and relatively low levels of openness to trade. They do not, in our analysis, materially influence the level of whole-economy productivity or GDP across the sample of countries examined, although they do influence productivity in particular sectors, in particular manufacturing. But the dispersion around this central finding is wide: the tendency for controls to depress productivity by encouraging rent-seeking sometimes is, and sometimes is not, counteracted by purposive government policy actions to maintain competitiveness. Whether or not this happens – whether, as we put it, controls are `smart´, and the manner in which they are smartened - is vital, on both efficiency and equity grounds. We devise a formula for, and make the case for capital controls which are time-limited, and contain an inbuilt incentive to increased productivity, as a means of improving the sustainability and equity of the adjustment process whilst keeping to a minimum the cost in terms of productive efficiency

Can Micro Health Insurance Reduce Poverty? Evidence from Bangladesh

This paper examines the impact of micro health insurance on poverty reduction in rural areas of Bangladesh. The research is based on household level primary data collected from the operating areas of the Grameen Bank during 2006. A number of outcome measures relating to poverty status are considered; these include household income, stability of household income via food sufficiency and ownership of non-land assets, and also the probability of being above or below the poverty line. The results show that micro health insurance has a positive association with all of these indicators, and this is statistically significant and quantitatively important for food sufficiency

Evaluating the Health Effects of Micro Health Insurance Placement: Evidence from Bangladesh

We examine the impact of micro health insurance placement on health awareness, healthcare utilization and health status of microcredit members in rural Bangladesh, using data from 329 households in the operating areas of Grameen Bank. The results are based on econometric analysis conditioned on placement of the scheme, and show that placement has a positive association with all of the outcomes. The results are statistically significant for health awareness and healthcare utilization, but not for heath status. Our study makes an important contribution to the literature as it provides evidence on the impact of MHI on a broad set of health outcomes

Exploring the limits of multiplexed photon-pair sources for the preparation of pure single-photon states

Current sources of heralded single photons based on nonlinear optics operate in a probabilistic manner. In order to build quantum-enhanced devices based around the use of single photons, compact, turn-key and deterministic sources are required. A possible solution is to multiplex a number of sources to increase the single-photon generation probability and in so doing reducing the waiting time to deliver large numbers of photons simultaneously, from independent sources. Previously it has been shown that, in the ideal case, 17 multiplexed sources allow deterministic generation of heralded single photons [Christ and Silberhorn, Phys. Rev. A 85, 023829 (2012)]. Here we extend this analysis to include undesirable effects of detector inefficiency and photon loss on a number of multiplexed sources using a variety of different detectors for heralding. We compare these systems for fixed signal-to-noise ratio to allow a direct comparison of performance for real- world heralded single photon sources.Comment: 10 pages, 7 figures. Equation 18 changed to include power of a half in the binomial facto

Temporal Loop Multiplexing: A resource efficient scheme for multiplexed photon-pair sources

Single photons are a vital resource for photonic quantum information processing. However, even state-of-the-art single photon sources based on photon-pair generation and heralding detection have only a low probability of delivering a single photon when one is requested. We analyse a scheme that uses a switched fibre delay loop to increase the delivery probability per time bin of single photons from heralded sources. We show that, for realistic experimental parameters, combining the output of up to 15 pulses can yield a performance improvement of a factor of 10. We consider the future performance of this scheme with likely component improvements.Comment: 5 pages, 4 figure

Pure single photon generation by type-I PDC with backward-wave amplification

We explore a promising method of generating pure heralded single photons. Our approach is based on parametric downconversion in a periodically-poled waveguide. However, unlike conventional downconversion sources, the photon pairs are counter-propagating: one travels with the pump beam in the forward direction while the other is backpropagating towards the laser source. Our calculations reveal that these downconverted two-photon states carry minimal spectral correlations within each photon-pair. This approach offers the possibility to employ a new range of downconversion processes and materials like PPLN (previously considered unsuitable due to their unfavorable phasematching properties) to herald pure single photons over a broad frequency range.Comment: 8 pages, 3 figures, minor text changes and reformattin