Heralded high-efficiency quantum repeater with atomic ensembles assisted by faithful single-photon transmission

Quantum repeater is one of the important building blocks for long distance quantum communication network. The previous quantum repeaters based on atomic ensembles and linear optical elements can only be performed with a maximal success probability of 1/2 during the entanglement creation and entanglement swapping procedures. Meanwhile, the polarization noise during the entanglement distribution process is harmful to the entangled channel created. Here we introduce a general interface between a polarized photon and an atomic ensemble trapped in a single-sided optical cavity, and with which we propose a high-efficiency quantum repeater protocol in which the robust entanglement distribution is accomplished by the stable spatial-temporal entanglement and it can in principle create the deterministic entanglement between neighboring atomic ensembles in a heralded way as a result of cavity quantum electrodynamics. Meanwhile, the simplified parity check gate makes the entanglement swapping be completed with unity efficiency, other than 1/2 with linear optics. We detail the performance of our protocol with current experimental parameters and show its robustness to the imperfections, i.e., detuning and coupling variation, involved in the reflection process. These good features make it a useful building block in long distance quantum communication.Comment: 11 pages, 10 figure

On the diameter of the Kronecker product graph

Let $G_1$ and $G_2$ be two undirected nontrivial graphs. The Kronecker product of $G_1$ and $G_2$ denoted by $G_1\otimes G_2$ with vertex set $V(G_1)\times V(G_2)$, two vertices $x_1x_2$ and $y_1y_2$ are adjacent if and only if $(x_1,y_1)\in E(G_1)$ and $(x_2,y_2)\in E(G_2)$. This paper presents a formula for computing the diameter of $G_1\otimes G_2$ by means of the diameters and primitive exponents of factor graphs.Comment: 9 pages, 18 reference

Fiscal Decentralization, the Composition of Public Spending, and Regional Growth in India

In this paper, we present an analytical model for examining the growth impact of intergovernmental and intersectoral allocation of public expenditure. The model helps us quantify the role of fiscal decentralization in regional economic growth and identify whether central and local allocation of public spending among various sectors are growth-enhancing. Applying our analytical framework to a panel data set of 16 major states in India, we have found that, in many cases of our regressions, fiscal decentralization is positively, and even statistically significantly, associated with state economic growth. The state allocation of public spending in various sectors is broadly consistent with "growth-maximizing", whereas increases in the central allocation of its budget among development projects, nondevelopment projects, and social and community services by cutting the center¡¯s spending on all other functions can promote regional growth. Furthermore, the distortionary effect of the state tax in India is dominated by the productive effect of tax-financed public spending, whereas the reverse holds for the central tax.

The growth impact of intersectoral and intergovernmental allocation of public expenditure: With applications to China and India

The negative association between fiscal decentralization and provincial economic growth has been found to be consistently significant and robust in China. For India, however, we have found that fiscal decentralization is positively, and even statistically significantly, associated with state economic growth. The state allocation of public spending in various sectors is broadly consistent with ¡°growth maximizing,¡± whereas increases in the central allocation of its budget among development projects, nondevelopment projects, and social and community services by cutting the center's spending on all other functions can promote regional growth.Fiscal decentralization, Public spending, Growth, Chinese economy, Indian economy