Quantum Key Distribution by Utilizing Four-Level Particles

We present a quantum key distribution protocol based on four-level particles entanglement. Furthermore, a controlled quantum key distribution protocol is proposed by utilizing three four-level particles. We show that the two protocols are secure.Comment: 5 pages, no figur

Detecting Lesion Bounding Ellipses With Gaussian Proposal Networks

Lesions characterized by computed tomography (CT) scans, are arguably often elliptical objects. However, current lesion detection systems are predominantly adopted from the popular Region Proposal Networks (RPNs) that only propose bounding boxes without fully leveraging the elliptical geometry of lesions. In this paper, we present Gaussian Proposal Networks (GPNs), a novel extension to RPNs, to detect lesion bounding ellipses. Instead of directly regressing the rotation angle of the ellipse as the common practice, GPN represents bounding ellipses as 2D Gaussian distributions on the image plain and minimizes the Kullback-Leibler (KL) divergence between the proposed Gaussian and the ground truth Gaussian for object localization. We show the KL divergence loss approximately incarnates the regression loss in the RPN framework when the rotation angle is 0. Experiments on the DeepLesion dataset show that GPN significantly outperforms RPN for lesion bounding ellipse detection thanks to lower localization error. GPN is open sourced at https://github.com/baidu-research/GP

Endogenous income taxes and indeterminacy in dynamic models: When Diamond meets Ramsey again.

This paper introduces fiscal increasing returns, through endogenous labor income tax rates as in Schmitt-Grohe and Uribe (1997), into the overlapping generations model with endogenous labor, consumption in both periods of life and homothetic preferences (e.g., Lloyd-Braga, Nourry and Venditti, 2007). We show that under numerical calibrations of the parameters, local indeterminacy can occur for distortionary tax rates that are empirically plausible for the U.S. economy, provided that the elasticity of capital-labor substitution and the wage elasticity of the labor supply are large enough, and the elasticity of intertemporal substitution in consumption is slightly greater than unity. These indeterminacy conditions are similar to those obtained within infinite horizon models and from this point of view, Diamond meets Ramsey again.Indeterminacy; Endogenous labor income tax rate.

Structure function of holographic quark-gluon plasma: Sakai-Sugimoto model versus its non-critical version

Motivated by recent studies of deep inelastic scattering (DIS) off the $\mathcal{N}=4$ super-Yang-Mills (SYM) plasma, holographically dual to $AdS_5\times S^5$ black hole, we in this note use the spacelike flavor current to probe the internal structure of one holographic quark-gluon plasma, which is described by the Sakai-Sugimoto model at high temperature phase (i.e., the chiral symmetric phase). The plasma structure function is extracted from the retarded flavor current-current correlator. Our main aim here is to explore the effect of non-conformality on these physical quantities. As usual, our study is under the supergravity approximation and the limit of large color number. Although the Sakai-Sugimoto model is non-conformal, which makes the calculations more involved than the well-studied $\mathcal {N}$=4 SYM case, the result seems to indicate that the non-conformality has little essential effect on the physical picture of the internal structure of holographic plasma, which is consistent with the intuition from the asymptotic freedom of QCD at high energy. While the physical picture underlying our investigation is same as the DIS off the $\mathcal {N}$=4 SYM plasma with(out) flavor, the plasma structure functions are quantitatively different, especially their scaling dependence on the temperature, which can be recognized as model-dependent. As a comparison, we also do the same analysis for the non-critical version of the Sakai-Sugimoto model which is conformal in the sense that it has a constant dilaton vacuum. The result for this non-critical model is much similar to the conformal $\mathcal{N}=4$ SYM plasma. We therefore attribute the above difference to the effect of non-conformality of the Sakai-Sugimoto model.Comment: 22 pages, no figure, Version accepted by Physical Review

Graphene-like Dirac states and Quantum Spin Hall Insulators in the square-octagonal MX2 (M=Mo, W; X=S, Se, Te) Isomers

We studied the square-octagonal lattice of the transition metal dichalcogenide MX$_2$ (with $M$=Mo, W; $X$=S, Se and Te), as an isomer of the normal hexagonal compound of MX$_2$. By band structure calculations, we observe the graphene-like Dirac band structure in a rectangular lattice of MX$_2$ with nonsymmorphic space group symmetry. Two bands with van Hove singularity points cross each at the Fermi energy, leading to two Dirac cones that locates at opposite momenta. Spin-orbit coupling can open a nontrivial gap at these Dirac points and induce the quantum spin Hall (QSH) phase, the 2D topological insulator. Here, square-octagonal MX$_2$ structures realize the interesting graphene physics, such as Dirac bands and QSH effect, in the transition metal dichalcogenides.Comment: 4 pages, 3 figures, 1 Tabl

Spectral function and quark diffusion constant in non-critical holographic QCD

Motivated by recent studies of intersecting D-brane systems in critical string theory and phenomenological AdS/QCD models, we present a detailed analysis for the vector and scalar fluctuations in a non-critical holographic QCD model in the high temperature phase, i.e., the chiral symmetric phase. This model is described by $N_f$ pairs of D4 and $\bar{\text{D4}}$ probe branes in a non-critical ${AdS_6}$ black hole background. Focusing on the hydrodynamic as well as the high frequency limit, we analytically obtain spectral functions for vector and scalar modes on the flavor probe. Then we extract the light quark diffusion constant for flavor current using three different methods and find that different methods give the same results. We also compute the heavy quark diffusion constant for comparison with the light quark case.Comment: 37 pages, no figures; Version to be published in Nuclear Physics

Are Progressive Income Taxes Stabilizing? : A Reply

Dromel and Pintus [Are Progressive Income Taxes Stabilizing?, Journal of Public Economic Theory 10, (2008) 329-349] have shown that labor-income tax progressivity reduces the likelihood of local indeterminacy, sunspots and cycles in a one sector monetary economy with constant returns to scale. In this note, we extend Dromel and Pintus (2008) into a two sector monetary economy with constant returns to scale studied by Bosi et al. (2007) and reassess the stabilizing effect of progressive income taxes. We show that the result in Dromel and Pintus (2008) is robust to this extension, which means that changes of the production structure won't affect the stabilizing effect of progressive income taxes, i.e., tax progressivity (regressivity) reduces (increases) the likelihood of local indeterminacy, sunspots and cycles.Tax Progressivity, local indeterminacy

Externalities, income taxes and indeterminacy in OLG models

Using an aggregate two-periods overlapping generations model with endogenous labor, consumption in both periods of life, homothetic preferences and productive external effects [Lloyd-Braga et al., 2007. Indeterminacy in dynamic models: When Diamond meets Ramsey. Journal of Economic Theory 134, 513-536], we examine the effects of alternative government financing methods on the range of values of increasing returns leading to indeterminacy. We show that under a large enough share of first period consumption over the wage income, local indeterminacy can easily occur for mild externalities if constant government expenditure is financed through either labor or capital income taxes. More precisely, we show that, with labor income taxes and mild externalities, small government expenditures are helpful to local indeterminacy, while large government expenditures are useful to stabilize the economy. With capital income taxes and mild externalities, local indeterminacy always exists. Moreover, we explore how our previous results are changed once government expenditure is endogenously determined for fixed rates on labor and capital income under the balanced-budget rule.Indeterminacy; Endogenous income tax rates; Externalities.