939 research outputs found

    For a few Euro more: Benefit Generosity and the Optimal Path of Unemployment Benefits

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    In this paper, we exploit the provision of higher UB at different points of the unemployment spell to shed light on the relative cost of insurance at different horizons after the job loss. First, we exploit a double cap system in an RDD setting to study the effect of higher benefit levels in the early part of unemployment spell on time on benefits and non-employment. We find that higher benefits increase the time spent on benefits and in non-employment, with no impact on new job quality. Second, we exploit an age-based discontinuity in benefit duration, which determines higher benefits later in the spell, to compare the behavioural and mechanical costs of these two variations in benefits. We find that the moral hazard costs are greater for higher benefit levels early in the spell. In addition, we provide evidence of a slight negative selection in long term unemployment and argue that the long-term unemployed face higher uncertainty in their employment prospects. These findings suggest that higher benefits later in the unemployment spell generate lower costs and would provide higher insurance. Our results question the optimality of strongly declining schedules for unemployment benefit levels

    Photon spin-to-orbital angular momentum conversion via an electrically tunable qq-plate

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    Exploiting electro-optic effects in liquid crystals, we achieved real-time control of the retardation of liquid- crystal-based qq-plates through an externally applied voltage. The newly conceived electro-optic qq-plates can be operated as electrically driven converters of photon spin into orbital angular momentum, enabling a variation of the orbital angular momentum probabilities of the output photons over a time scale of milliseconds.Comment: 4 pages, 5 figures, submitte

    On the Analytic Structure of a Family of Hyperboloidal Beams of Potential Interest for Advanced LIGO

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    For the baseline design of the advanced Laser Interferometer Gravitational-wave Observatory (LIGO), use of optical cavities with non-spherical mirrors supporting flat-top ("mesa") beams, potentially capable of mitigating the thermal noise of the mirrors, has recently drawn a considerable attention. To reduce the severe tilt-instability problems affecting the originally conceived nearly-flat, "Mexican-hat-shaped" mirror configuration, K. S. Thorne proposed a nearly-concentric mirror configuration capable of producing the same mesa beam profile on the mirror surfaces. Subsequently, Bondarescu and Thorne introduced a generalized construction that leads to a one-parameter family of "hyperboloidal" beams which allows continuous spanning from the nearly-flat to the nearly-concentric mesa beam configurations. This paper is concerned with a study of the analytic structure of the above family of hyperboloidal beams. Capitalizing on certain results from the applied optics literature on flat-top beams, a physically-insightful and computationally-effective representation is derived in terms of rapidly-converging Gauss-Laguerre expansions. Moreover, the functional relation between two generic hyperboloidal beams is investigated. This leads to a generalization (involving fractional Fourier transform operators of complex order) of some recently discovered duality relations between the nearly-flat and nearly-concentric mesa configurations. Possible implications and perspectives for the advanced LIGO optical cavity design are discussed.Comment: 9 pages, 6 figures, typos corrected, Eqs. (24) and (26) change

    Experimental investigation on the geometry of GHz states

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    Nonclassical correlations arising in complex quantum networks are attracting growing interest, both from afundamental perspective and for potential applications in information processing. In particular, in an entanglementswapping scenario a new kind of correlations arise, the so-called nonbilocal correlations that are incompatible withlocal realism augmented with the assumption that the sources of states used in the experiment are independent.In practice, however, bilocality tests impose strict constraints on the experimental setup and in particular to thepresence of shared reference frames between the parties. Here, we experimentally address this point showing thatfalse positive nonbilocal quantum correlations can be observed even though the sources of states are independent.To overcome this problem, we propose and demonstrate a scheme for the violation of bilocality that does notrequire shared reference frames and thus constitutes an important building block for future investigations ofquantum correlations in complex network

    Device-independent certification of high-dimensional quantum systems

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    An important problem in quantum information processing is the certification of the dimension of quantum systems without making assumptions about the devices used to prepare and measure them, that is, in a device-independent manner. A crucial question is whether such certification is experimentally feasible for high-dimensional quantum systems. Here we experimentally witness in a device-independent manner the generation of six-dimensional quantum systems encoded in the orbital angular momentum of single photons and show that the same method can be scaled, at least, up to dimension 13.Comment: REVTeX4, 5 pages, 2 figure
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