Quantum-capacity bounds in spin-network communication channels

Using the Lieb-Robinson inequality and the continuity property of the quantum capacities in terms of the diamond norm, we derive an upper bound on the values that these capacities can attain in spin-network communication i.i.d. models of arbitrary topology. Differently from previous results we make no assumptions on the encoding mechanisms that the sender of the messages adopts in loading information on the network.Comment: 9 pages, 1 figur

Optimal Quantum Subtracting Machine

The impossibility of undoing a mixing process is analysed in the context of quantum information theory. The optimal machine to undo the mixing process is studied in the case of pure states, focusing on qubit systems. Exploiting the symmetry of the problem we parametrise the optimal machine in such a way that the number of parameters grows polynomially in the size of the problem. This simplification makes the numerical methods feasible. For simple but non-trivial cases we computed the analytical solution, comparing the performance of the optimal machine with other protocols.Comment: 13 pages, 2 figure

The “China effect” on EU Exports to OECD markets – A focus on Italy

This paper analyzes the indirect impact of China on the export performance of major European countries (Italy, France, Germany and Spain) in their main destination markets (OECD countries). Given a strong specialization in manufacturing sector, these EU countries are likely to be at risk from China’s competition, especially in consumer goods. The heterogeneity in the production (and export) structures of EU countries makes Italy, whose productive structure is based on so-called “traditional” sectors, most vulnerable to China’s competitive pressure. Using data for the period 1995-2009, this paper estimates the possible displacement effect at sector level. Results show that there is a considerable variation in different EU countries’ exposure to China’s competition and that, in some sectors the Chinese exports effect is, indeed, strong. This is particularly true for the more recent period, after China has entered WTO and for Italy, both in traditional and more capital intensive sectors.china, trade, italy, gravity model

El Shincal y Los Colorados en el paisaje : marco geográfico y natural

Fil: Giovannetti, Marco Antonio. División Arqueología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

A proposal for the recovery of archaeobotanical mi-croremains in non-mobile mortars

La investigación de microvestigios vegetales, también conocidos como microrrestos, ha evolucionado con rapidez en los últimos años de la práctica arqueológica en general. Como parte de lo que se conoce como especialización arqueobotánica el estudio de los granos de almidón, fitolitos, fibras celulares y algunos otros elementos orgánicos de las plantas han sido interpelados por la arqueología dando buenos resultados en diversos tipos de problemas (Coil et al. 2003). Estos vestigios arqueológicos han sido recuperados desde distintos tipos de objetos y/o espacios que se hipotetizaba -a veces con sólidas bases inferenciales y otras no tanto- estuvieron en contacto directo con vegetales. Es el caso de objetos arqueológicos líticos como hachas, raspadores e instrumentos de molienda, tanto el componente activo (mano de moler) como pasivo (la cavidad que posee varios nombres dependiendo de los tipos) sobre los que se comprobó la eficacia de esta técnica1. Recientemente también se está comenzando a explorar el potencial de hallazgo sobre piezas cerámicas y piezas dentales humanas (Zucol et al 2008, Lantos et al 2012, Musoubach 2012). En esta presentación nos interesa brindar un método para una correcta y productiva recolección de muestras con posibles microrrestos vegetales en un tipo de restos arqueológicos particulares como es el caso de los morteros fijos, artefactos constituidos sobre grandes bloques inmóviles, muy comunes en algunas regiones de nuestro país como el Noroeste Argentino (NOA) y Sierras Centrales de Argentina. La especificidad de este tipo de instrumento de molienda ha sido muy poco estudiada siendo en general tratados sin independencia de los objetos móviles. En determinados trabajos (Nelson y Lippmeier 1993) es posible consignarlos y analizarlos como parte del moviliario fijo y duradero de sitios arqueológicos (site fourniture) y por ende pasibles de reutilización. Exactamente desde aquí nace la necesidad de particularizarlos desde sus propias características y potencialidades, es decir dado que son objetos inmóviles que deben ser trabajados en el campo, requieren de una metodología propia para la extracción de restos analizables en laboratorio. Los morteros móviles, en cambio, pueden ser transportados al gabinete de trabajo y allí mismo extraer las muestras para recuperar, describir e identificar los microrrestos vegetales.Fil: Giovannetti, Marco Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Arqueología; Argentin

Modulated phases of graphene quantum Hall polariton fluids

There is growing experimental interest in coupling cavity photons to the cyclotron resonance excitations of electron liquids in high-mobility semiconductor quantum wells or graphene sheets. These media offer unique platforms to carry out fundamental studies of exciton-polariton condensation and cavity quantum electrodynamics in a regime in which electron-electron interactions are expected to play a pivotal role. Focusing on graphene, we present a theoretical study of the impact of electron-electron interactions on a quantum Hall polariton fluid, that is a fluid of magneto-excitons resonantly coupled to cavity photons. We show that electron-electron interactions are responsible for an instability of graphene integer quantum Hall polariton fluids towards a modulated phase. We demonstrate that this phase can be detected by measuring the collective excitation spectra, which soften at a characteristic wave vector of the order of the inverse magnetic length.Comment: 26+17 pages, 5+3 figure

Charger-mediated energy transfer for quantum batteries: an open system approach

The energy charging of a quantum battery is analyzed in an open quantum setting, where the interaction between the battery element and the external power source is mediated by an ancilla system (the quantum charger) that acts as a controllable switch. Different implementations are analyzed putting emphasis on the interplay between coherent energy pumping mechanisms and thermalization

Theory of integer quantum Hall polaritons in graphene

We present a theory of the cavity quantum electrodynamics of the graphene cyclotron resonance. By employing a canonical transformation, we derive an effective Hamiltonian for the system comprised of two neighboring Landau levels dressed by the cavity electromagnetic field (integer quantum Hall polaritons). This generalized Dicke Hamiltonian, which contains terms that are quadratic in the electromagnetic field and respects gauge invariance, is then used to calculate thermodynamic properties of the quantum Hall polariton system. Finally, we demonstrate that the generalized Dicke description fails when the graphene sheet is heavily doped, i.e. when the Landau level spectrum of 2D massless Dirac fermions is approximately harmonic. In this case we `integrate out' the Landau levels in valence band and obtain an effective Hamiltonian for the entire stack of Landau levels in conduction band, as dressed by strong light-matter interactions.Comment: 20 pages, 7 figure

Commercial plant-probiotic microorganisms for sustainable organic tomato production systems

Selected plant-probiotic microorganisms, produced by the company CCS Aosta at a commercial scale, are being tested in the Italian Padana plain in open field conditions for their ability to provide adequate crop nutrition and to ensure durable soil fertility for organic tomato production. In this three-years-long project the QLIF-WP333 research team will investigate the potential of soil probiotics management as a tool to improve the quality of tomato fruits and the sustainability of organic tomato production systems