Generation Engineering of Heralded Narrowband Colour Entangled States

Efficient heralded generation of entanglement together with its manipulation is of great importance for quantum communications. In addition, states generated with bandwidths naturally compatible with atomic transitions allow a more efficient mapping of light into matter which is an essential requirement for long distance quantum communications. Here we propose a scheme where the indistinguishability between two spontaneous four-wave mixing processes is engineered to herald generation of single-photon frequency-bin entangled states, i.e., single-photons shared by two distinct frequency modes. We show that entanglement can be optimised together with the generation probability, while maintaining absorption negligible. Besides, the scheme illustrated for cold rubidium atoms is versatile and can be implemented in several other physical systems

Log-mean linear models for binary data

This paper introduces a novel class of models for binary data, which we call log-mean linear models. The characterizing feature of these models is that they are specified by linear constraints on the log-mean linear parameter, defined as a log-linear expansion of the mean parameter of the multivariate Bernoulli distribution. We show that marginal independence relationships between variables can be specified by setting certain log-mean linear interactions to zero and, more specifically, that graphical models of marginal independence are log-mean linear models. Our approach overcomes some drawbacks of the existing parameterizations of graphical models of marginal independence

Radiation 'damping' in atomic photonic crystals

The force exerted on a material by an incident beam of light is dependent upon the material's velocity in the laboratory frame of reference. This velocity dependence is known to be diffcult to measure, as it is proportional to the incident optical power multiplied by the ratio of the material velocity to the speed of light. Here we show that this typically tiny effect is greatly amplified in multilayer systems composed of resonantly absorbing atoms (e.g. optically trapped 87Rb), which may exhibit ultra-narrow photonic band gaps. The amplification of the effect is shown to be three orders of magnitude greater than previous estimates for conventional photonic-band-gap materials, and significant for material velocities of a few ms/s.Comment: 5 pages, 3 figure

Synchronization in interacting Scale Free Networks

We study the fluctuations of the interface, in the steady state, of the Surface Relaxation Model (SRM) in two scale free interacting networks where a fraction $q$ of nodes in both networks interact one to one through external connections. We find that as $q$ increases the fluctuations on both networks decrease and thus the synchronization reaches an improvement of nearly $40\%$ when $q=1$. The decrease of the fluctuations on both networks is due mainly to the diffusion through external connections which allows to reducing the load in nodes by sending their excess mostly to low-degree nodes, which we report have the lowest heights. This effect enhances the matching of the heights of low-and high-degree nodes as $q$ increases reducing the fluctuations. This effect is almost independent of the degree distribution of the networks which means that the interconnection governs the behavior of the process over its topology.Comment: 13 pages, 7 figures. Added a relevant reference.Typos fixe

Local banking development and the use of debt financing by new firms

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordWe investigate the effects of local banking development on the debt financing of new firms using a large sample of Italian firms. Controlling for potential endogeneity issues, we find that new firms are more likely to use bank debt and have higher leverage in provinces with more bank branches relative to population. However, it is important to account for bank heterogeneity. For instance, more foreign banks in a province actually reduce access to bank debt. Taken together, our study provides new and nuanced evidence on the role of local banking development for the debt financing of new firms

Radiation pressure in stratified moving media

Copyright © 2012 American Physical SocietyA general theory of optical forces on moving bodies is here developed in terms of generalized 4×4 transfer and scattering matrices. Results are presented for a planar dielectric of arbitrary refractive index placed in an otherwise empty space and moving parallel and perpendicular to the slab-vacuum interface. In both regimes of motion the resulting force comprises lateral and normal velocity-dependent components, which may depend in a subtle way on the Doppler effect and s-p-polarization mixing. For lateral displacements in particular, polarization mixing, which is here interpreted as an effective magnetoelectric effect due to the reduced symmetry induced by the motion of the slab, gives rise to a velocity-dependent force contribution that is sensitive to the phase difference between the two polarization amplitudes. This term gives rise to a rather peculiar optical response on the moving body, and specific cases are illustrated for incident radiation of arbitrarily directed linear polarization. The additional force due to polarization mixing may cancel to first order in V/c with the first order Doppler contribution yielding an overall vanishing of the velocity-dependent component of the force on the body. The above findings bear some relevance to modern developments of nano-optomechanics and to the problem of the frictional component of the Casimir force

Seismic Surveillance of Active Volcanoes: The Osservatorio Vesuviano Seismic Network (OVSN, Southern Italy)

Since 1970 the Osservatorio Vesuviano (Vesuvius Observatory of Naples, Italy) has maintained local seismic networks to monitor the active volcanoes of the Neapolitan area (Vesuvio, Campi Flegrei, Ischia island) as well as the most active seismic zone of the Campania Region and Southern Apennines. During 2000-2001 the local seismic networks in the volcanic regions and the regional network were restructured and unified to form the Osservatorio Vesuviano Seismic Network (OVSN) with the purpose of improving the quality of the recorded data and the consistency of data processing