How does the composition of public spending matter?

Public spending has effects which are complex to trace and difficult to quantify. But the composition of public expenditure has become the key instrument by which development agencies seek to promote economic development. In recent years, the development assistance to heavily indebted poor countries (HIPCs) hasbeen made conditional on increased expenditure on categories that are thought to be"pro-poor". This paper responds to the growing concern being expressed about the conceptual foundations and the empirical basis for the belief that poverty can be reduced through targeted public spending. While it is widely accepted that growth and redistribution are important sources of reduction in absolute poverty, a review of the literature confirms the lack of an appropriate theoretical framework for assessing the impact of public spending on growth as well as poverty. There is a need to combine principles of both public economics and growth theory to develop appropriate theoretical guidance for public expenditure policy. This paper identifies a number of approaches that are beginning to address this gap. Building on these approaches, it proposes a framework that has its foundation in a broadly articulated development strategy and its economic goals such as growth, equity, and poverty reduction. It recommends the use of public economics principles to clarify the roles of the private and public sectors and to recognize the complementarity of spending, taxation, and regulatory instruments available to affect public policy. With regard to the impact of any given type of public spending, policy recommendations must be tailored to countries and be based on empirical analysis that takes account of the lags and leads in their effects on equity and growth and ultimately on poverty. The paper sketches out such a framework as the first step in what will have to be a longer-term research agenda to provide theoretically and empirically robust and verifiable guidance to public spending policy.Poverty Assessment,Achieving Shared Growth,Environmental Economics&Policies,Health Economics&Finance,Governance Indicators

Returns to education in the economic transition : a systematic assessment using comparable data

This paper examines the assertion that returns to schooling increase as an economy transitions to a market environment. This claim has been difficult to assess as existing empirical evidence covers only a few countries over short time periods. A number of studies find that returns to education increased from the"pre-transition"period to the"early transition"period. It is not clear what has happened to the skills premium through the late 1990s, or the period thereafter. The authors use data that are comparable across countries and over time to estimate returns to schooling in eight transition economies (Bulgaria, Czech Republic, Hungary, Latvia, Poland, Russia, Slovak Republic, and Slovenia) from the early transition period up to 2002. In the case of Hungary, they capture the transition process more fully, beginning in the late 1980s. Compared to the existing literature, they implement a more systematic analysis and perform more comprehensive robustness checks on the estimated returns, although at best they offer only an incomplete solution to the problem of endogeneity. The authors find that the evidence of a rising trend in returns to schooling over the transition period is generally weak, except in Hungary and Russia where there have been sustained and substantial increases in returns to schooling. On average, the estimated returns in the sample are comparable to advanced economy averages. There are, however, significant differences in returns across countries and these differentials have remained roughly constant over the past 15 years. They speculate on the likely institutional and structural factors underpinning these results, including incomplete transition and significant heterogeneity and offsetting developments in returns to schooling within countries.Education For All,Primary Education,Teaching and Learning,Education Reform and Management,Access&Equity in Basic Education

Landauer's principle in multipartite open quantum system dynamics

We investigate the link between information and thermodynamics embodied by Landauer's principle in the open dynamics of a multipartite quantum system. Such irreversible dynamics is described in terms of a collisional model with a finite temperature reservoir. We demonstrate that Landauer's principle holds, for such a configuration, in a form that involves the flow of heat dissipated into the environment and the rate of change of the entropy of the system. Quite remarkably, such a principle for {\it heat and entropy power} can be explicitly linked to the rate of creation of correlations among the elements of the multipartite system and, in turn, the non-Markovian nature of their reduced evolution. Such features are illustrated in two exemplary cases.Comment: 5 pages, 3 figures, RevTeX4-1; Accepted for publication in Phys. Rev. Let

Experimental Demonstration of Decoherence-Free One-Way Information Transfer

We report the experimental demonstration of a one-way quantum protocol reliably operating in the presence of decoherence. Information is protected by designing an appropriate decoherence-free subspace for a cluster state resource. We demonstrate our scheme in an all-optical setup, encoding the information into the polarization states of four photons. A measurement-based one-way information-transfer protocol is performed with the photons exposed to severe symmetric phase-damping noise. Remarkable protection of information is accomplished, delivering nearly ideal outcomes.Comment: 5 pages, 3 figures, RevTeX

Experimental realization of Dicke states of up to six qubits for multiparty quantum networking

We report the first experimental generation and characterization of a six-photon Dicke state. The produced state shows a fidelity of F=0.56+/-0.02 with respect to an ideal Dicke state and violates a witness detecting genuine six-qubit entanglement by four standard deviations. We confirm characteristic Dicke properties of our resource and demonstrate its versatility by projecting out four- and five-photon Dicke states, as well as four-photon GHZ and W states. We also show that Dicke states have interesting applications in multiparty quantum networking protocols such as open-destination teleportation, telecloning and quantum secret sharing.Comment: 4 pages, 4 figures, RevTeX

Irreversibility and the arrow of time in a quenched quantum system

Irreversibility is one of the most intriguing concepts in physics. While microscopic physical laws are perfectly reversible, macroscopic average behavior has a preferred direction of time. According to the second law of thermodynamics, this arrow of time is associated with a positive mean entropy production. Using a nuclear magnetic resonance setup, we measure the nonequilibrium entropy produced in an isolated spin-1/2 system following fast quenches of an external magnetic field and experimentally demonstrate that it is equal to the entropic distance, expressed by the Kullback-Leibler divergence, between a microscopic process and its time-reverse. Our result addresses the concept of irreversibility from a microscopic quantum standpoint.Comment: 8 pages, 7 figures, RevTeX4-1; Accepted for publication Phys. Rev. Let

Experimental realization of a quantum game on a one-way quantum computer

We report the first demonstration of a quantum game on an all-optical one-way quantum computer. Following a recent theoretical proposal we implement a quantum version of Prisoner's Dilemma, where the quantum circuit is realized by a 4-qubit box-cluster configuration and the player's local strategies by measurements performed on the physical qubits of the cluster. This demonstration underlines the strength and versatility of the one-way model and we expect that this will trigger further interest in designing quantum protocols and algorithms to be tested in state-of-the-art cluster resources.Comment: 13 pages, 4 figure

Photon production from the vacuum close to the super-radiant transition: When Casimir meets Kibble-Zurek

The dynamical Casimir effect (DCE) predicts the generation of photons from the vacuum due to the parametric amplification of the quantum fluctuation of an electromagnetic field\cite{casimir1,casimir2}. The verification of such effect is still elusive in optical systems due to the very demanding requirements of its experimental implementation. This typically requires very fast changes of the boundary conditions of the problem, such as the high-frequency driving of the positions of the mirrors of a cavity accommodating the field. Here, we show that an ensemble of two-level atoms collectively coupled to the electromagnetic field of a cavity (thus embodying the quantum Dicke model\cite{dicke}), driven at low frequencies and close to a quantum phase transition, stimulates the production of photons from the vacuum. This paves the way to an effective simulation of the DCE through a mechanism that has recently found an outstanding experimental demonstration\cite{esslinger}. The spectral properties of the emitted radiation reflect the critical nature of the system and allow us to link the detection of DCE to the Kibble-Zurek mechanism for the production of defects when crossing a continuous phase transition\cite{KZ1,KZ2}. We illustrate the features of our proposal by addressing a simple cavity quantum-electrodynamics (cQED) setting of immediate experimental realisation.Comment: 4+1 pages, major changes in the second part of the paper. To appear in Physical Review Letter

Self-cooling of a micro-mirror by radiation pressure

We demonstrate passive feedback cooling of a mechanical resonator based on radiation pressure forces and assisted by photothermal forces in a high-finesse optical cavity. The resonator is a free-standing high-reflectance micro-mirror (of mass m=400ng and mechanical quality factor Q=10^4) that is used as back-mirror in a detuned Fabry-Perot cavity of optical finesse F=500. We observe an increased damping in the dynamics of the mechanical oscillator by a factor of 30 and a corresponding cooling of the oscillator modes below 10 K starting from room temperature. This effect is an important ingredient for recently proposed schemes to prepare quantum entanglement of macroscopic mechanical oscillators.Comment: 11 pages, 9 figures, minor correction