Optimization of photon storage fidelity in ordered atomic arrays

A major application for atomic ensembles consists of a quantum memory for light, in which an optical state can be reversibly converted to a collective atomic excitation on demand. There exists a well-known fundamental bound on the storage error, when the ensemble is describable by a continuous medium governed by the Maxwell-Bloch equations. The validity of this model can break down, however, in systems such as dense, ordered atomic arrays, where strong interference in emission can give rise to phenomena such as subradiance and "selective" radiance. Here, we develop a general formalism that finds the maximum storage efficiency for a collection of atoms with discrete, known positions, and a given spatial mode in which an optical field is sent. As an example, we apply this technique to study a finite two-dimensional square array of atoms. We show that such a system enables a storage error that scales with atom number $N_\mathrm{a}$ like $\sim (\log N_\mathrm{a})^2/N_\mathrm{a}^2$, and that, remarkably, an array of just $4 \times 4$ atoms in principle allows for an efficiency comparable to a disordered ensemble with optical depth of around 600.Comment: paper is now identical to published versio

Multicomponent reaction-diffusion processes on complex networks

We study the reaction-diffusion process $A + B \to \emptyset$ on uncorrelated scale-free networks analytically. By a mean-field ansatz we derive analytical expressions for the particle pair-correlations and the particle density. Expressing the time evolution of the particle density in terms of the instantaneous particle pair-correlations, we determine analytically the `jamming' effect which arises in the case of multicomponent, pair-wise reactions. Comparing the relevant terms within the differential equation for the particle density, we find that the `jamming' effect diminishes in the long-time, low-density limit. This even holds true for the hubs of the network, despite that the hubs dynamically attract the particles.Comment: 8 pages, 6 figure

Strongly inhibited transport of a 1D Bose gas in a lattice

We report the observation of strongly damped dipole oscillations of a quantum degenerate 1D atomic Bose gas in a combined harmonic and optical lattice potential. Damping is significant for very shallow axial lattices (0.25 photon recoil energies), and increases dramatically with increasing lattice depth, such that the gas becomes nearly immobile for times an order of magnitude longer than the single-particle tunneling time. Surprisingly, we see no broadening of the atomic quasimomentum distribution after damped motion. Recent theoretical work suggests that quantum fluctuations can strongly damp dipole oscillations of 1D atomic Bose gas, providing a possible explanation for our observations.Comment: 5 pages, 4 figure

EFFECT OF SUPERHEATING DEGREE AND PRESSURE ON EFFICIENCY OF AN ORES (ORGANIC RANKINE ENERGY STORAGE) SYSTEM

The increased share of intermittent renewable energy sources has led to the development of new energy storage solutions to mitigate the effects of the variability of energy supply. CAES (Compressed Air Energy Storage) and LAES (Liquid Air Energy Storage) are two of the main solutions for medium to large-scale systems for long-term energy storage. However, both are limited; the first requires the availability of suitable geological formations and the second requires considerable investment because of the required liquefaction process. This work aims to evaluate the thermodynamic performance of an energy storage system, called Organic Rankine Energy Storage (ORES), with a focus on the effects of pressure and superheating degree at the expander inlet on the round-trip efficiency (i.e. ratio of generated energy during energy discharge over consumed energy during energy storage) of the system. The system was evaluated for six organic fluids which were selected based on commercial maturity, environmental impacts, and safety conditions, namely R-134a, R-152a, R-142b, R-236ea, R-365mfc, and R-141b. The efficiency of the system was obtained for each of those fluids using a steady-state model approximation of the operation of the system and for pressures at the expander inlet varying from 675 kPa up to 4,300 kPa (or 95% of the critical pressure, if lower) and for superheating degrees from 0 up to 40 K. The evaluation of the system for six organic fluids as working fluid resulted in round-trip efficiencies around 70 % (comparable to both CAES and LAES when subject to similar methodologies) with higher sensitivity to pressure than to superheating degree. For all fluids, an increase of 5 K in the superheating degree resulted in an absolute decrease of 2-5% in the round-trip efficiency. Effects of pressure were more diverse, R-152b, R-134a and R-142b showed an average reduction of 10% in efficiency for each reduction of 500 kPa in pressure (in the high efficiency operation region, while R-365mfc and R-141b were much less affected, around 5% decrease in efficiency for each reduction of 500 kPa. The fluids that had the highest efficiencies and that also presented a high efficiency for a wider range of pressures were the R141b and R365mfc, which are also the fluids with the highest critical temperatures

Análise global da expressão de genes Dof em videira.

Neste trabalho é caracterizada a família gênica Dof em videira (Vitis vinifera L.), a qual é composta por 25 genes. A busca por domínios conservados foi realizada utilizando-se o programa MEME suite v.4.9.0. Estudos filogenéticos foram conduzidos comparando 163 sequências Dof de videira, álamo, Arabidopsis thaliana e tomate com proteínas Dof de função conhecida previamente descritos na literatura

Utilizacao de materiais flutuantes no controle da evaporacao no Tropico Semi-Arido (TSA).

Materiais flutuantes foram testados em tanques tipo Classe A, com o objetivo de reduzir as perdas por evaporacao das superficies livres d'agua. As coberturas consistiram de discos impoermaveis compostos de vermiculita, parafina e cera de carnauba (Copernicia cerifera Mart.); esferas de barro vitrificadas; esferas de barro nao vitrificadas; e discos de isopor impreganados de uma mistura de cera de carnauba mais parafina derretida. Cada tratamento cobriu 80% da superficie exposta do tanque, apresentando os seguintes resultados no controle das perdas: 54%, 60%, 50% e 61% respectivamente. A eficiencia apresentada indicou que as coberturas empregadas poderao ser viaveis

Preparing and probing atomic number states with an atom interferometer

We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave double-slit diffraction pattern. The time evolution of the double-slit diffraction pattern is used to measure the number statistics of the input state. The flexibility of our double well lattice provides a means to detect the presence of empty lattice sites, an important and so far unmeasured factor in determining the purity of a Mott state