The quantum optical description of three experiments involving non-linear optics using a graphical method

In this paper we describe and thoroughly discuss three reported experiments in quantum optics (QO) involving interferometers and non-linear crystals. We show that by using a graphical method and an over-simplified model of the parametric down-conversion process, we arrive to explain all the important results reported in the respective papers. Indistinguishability is discussed in the case of separable/non-separable (i.e. entangled) quantum systems and our interpretation is sometimes at variance with the one given by the authors reporting the experiments.Comment: 6 pages, 6 figure

Field operator transformations in Quantum Optics using a novel graphical method with applications to beam splitters and interferometers

In this paper we describe a novel, graphical method, allowing the fast computation of field operator transformations for linear lossless optical devices in Quantum Optics (QO). The advantage of this method grows with the complexity of the considered optical setup. As case studies we examine the field operator transformations for the beam splitter (BS), the Mach-Zehnder interferometer (MZI) and the double MZI. We consider the simple case with monochromatic input light, as well as extensions to the non-monochromatic case.Comment: 6 pages, 8 figure; to appear in EPJ

Consensus, institutions, and supply response : the political economy of agricultural reforms in Sub-Saharan Africa

During the late 1980s and the 1990s, most countries in Sub-Saharan Africa implemented agricultural policy reforms, along with national political and economic reforms. The agricultural reforms focused on opening up processing and marketing activities to increased competition and eliminating export taxes and restrictions to improve producer incentives. In eight of nine country/commodity case studies analyzed in this paper, output responded positively in the short run to the reforms. In many cases, however, the initial supply response was not sustained in the face of subsequent shocks. The studies suggest that stakeholder consensus on the distribution of sector-specific rents is a key variable affecting the sustainability of supply responses. Agricultural sector reforms lead to large changes in income distribution. The greater the acceptance of the distribution of rents following the reforms, the better sectors are able to accommodate subsequent shocks. In cases where the initial consensus on the distribution of rents is weak, shocks lead to reform reversals in some cases or an inability to design necessary support institutions in others. The diversity in outcomes across similar products and countries suggests it is possible to achieve sector and local level results that differ from national ones.Markets and Market Access,Crops&Crop Management Systems,Emerging Markets,Economic Theory&Research,Labor Policies

Growth before and after trade liberalization

The empirical study of the impact of trade liberalization has not convinced the skeptics about the economic gains after trade reforms. Some have even argued that trade reforms have led to economic collapse and to deindustrialization. Using a sample that excludes countries that were subject to major exogenous disruptions, the authors note that post-reform economic growth was 1.2 percentage points higher than before the reforms. This is remarkable considering that pre-reform periods were characterized by highly expansionary state policies and large external borrowing, and the crisis years that preceded trade liberalization in the comparisons are eliminated. Through multivariate fixed effects estimations the authors calculate that annual per capita GDP growth rates increased by up to 2.6 percentage points after the trade reforms, compared to a counterfactual that takes into consideration the evolution of several growth determinants. Moreover, trade liberalization has been followed by an acceleration of growth in investment, exports of goods and services, and manufacturing exports, and as opposed to common belief, outward orientation did not lead to significant deindustrialization and actually seems to have increased export diversification. Growth acceleration occurred irrespective of income per capita level and was quite significant in Sub-Saharan Africa. As expected, small countries benefited most from the reforms.Economic Theory&Research,Free Trade,Achieving Shared Growth,Trade Law,Trade Policy

Mozambique Cashew reforms revisited

Cashew policy reforms in Mozambique have been controversial. They are often invoked by critics as an illustration of how agricultural policy reforms supported by international financial institutions may fail to have their intended effects. This paper revisits the reforms and their outcomes almost two decades later. While the reforms resulted in higher producer prices and an increase in output, lack of consensus on the specifics of the reforms and associated non-price support arrangements created a situation in which the sector was not able to withstand international price shocks that ultimately led to a collapse of both the processing industry and cashew production. Non-price support by donors improved the efficiency of the processing industry but this was not complemented by an expansion in cashew nut supply as such support did not extend to smallholder cashew producers. For the reforms to have had their intended results, greater investment in -- and support to -- smallholder production was needed to increase yields and overall output. Such a more comprehensive approach to cashew policy reform would have required a greater focus on achieving consensus on the causes of the cashew sector's problems and agreement by all stakeholders on a common institutional framework for pricing and non-price support.Markets and Market Access,Emerging Markets,Economic Theory&Research,Access to Markets,E-Business

Imports , exports , and industrial performance in India , 1970-88

In the 1960's and 1970's, India's policy of encouraging self-sufficiency by restricting imports was complemented by regulation of all facets of the industrial environment. Still, India developed a large, diversified manufacturing sector. In 1977-78, the policy environment began to change - with a relaxing of import controls and restrictions that has continued until now. With reform of industrial policies and a more expansionary macroeconomic policy, the value added in manufacturing grew from 4.5 percent a year in the 1970's to 7.9 percent a year in the 1980's. Meanwhile, gradual depreciation of the currency since 1985 has encouraged exports and brought prices in India closer to world levels. The faster growth of output and productivity in the 1980's is a welcome change from India's earlier stagnation. But deteriorating macroeconomic balances have brought India to a balance of payments crisis. Changes in tariffs and other instruments have more than compensated for relaxation of the import regime. Foreign trade has contracted relative to domestic output, despite some relaxation of quantity restrictions and attempts to increase exports. The main reason for this decline has been the increase in import prices relative to domestic output because of increasing tariffs, large real devaluations (especially after 1986), and rapidly expnanding domestic demand, which have made the domestic market more attractive than exports. Policy reform has led to faster growth of manufacturing output and productivity, but the main force behind faster growth has been increased public spending fueled by growing fiscal deficits. Another important variable has been a more accommodating import policy sustained by large external borrowings. This pattern of growth is not sustainable because of significant internal and external debt stocks that have accumulated over the last decade. Macroeconomic and trade policy must change significantly to shift the economy to a more export-oriented path - both to overcome the foreign exchange shortages and to rely more on external demand for industrial output. The authors argue that the manufacturing sector is highly responsive to relative price changes. Pessimism about elasticity has pervaded Indian policy making but they show high elasticities, indicating that the economy would respond favorably to changes in incentives.Economic Theory&Research,Environmental Economics&Policies,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Consumption,Trade Policy