Optimization of Short Coherent Control Pulses

The coherent control of small quantum system is considered. For a two-level system coupled to an arbitrary bath we consider a pulse of finite duration. We derive the leading and the next-leading order corrections to the evolution operator due to the non-commutation of the pulse and the bath Hamiltonian. The conditions are computed that make the leading corrections vanish. The pulse shapes optimized in this way are given for $\pi$ and $\frac{\pi}{2}$ pulses.Comment: 9 pages, 6 figures; published versio

Generalization of short coherent control pulses: extension to arbitrary rotations

We generalize the problem of the coherent control of small quantum systems to the case where the quantum bit (qubit) is subject to a fully general rotation. Following the ideas developed in Pasini et al (2008 Phys. Rev. A 77, 032315), the systematic expansion in the shortness of the pulse is extended to the case where the pulse acts on the qubit as a general rotation around an axis of rotation varying in time. The leading and the next-leading corrections are computed. For certain pulses we prove that the general rotation does not improve on the simpler rotation with fixed axis.Comment: 6 pages, no figures; published versio

Hidden order in bosonic gases confined in one dimensional optical lattices

We analyze the effective Hamiltonian arising from a suitable power series expansion of the overlap integrals of Wannier functions for confined bosonic atoms in a 1d optical lattice. For certain constraints between the coupling constants, we construct an explicit relation between such an effective bosonic Hamiltonian and the integrable spin-$S$ anisotropic Heisenberg model. Therefore the former results to be integrable by construction. The field theory is governed by an anisotropic non linear $\sigma$-model with singlet and triplet massive excitations; such a result holds also in the generic non-integrable cases. The criticality of the bosonic system is investigated. The schematic phase diagram is drawn. Our study is shedding light on the hidden symmetry of the Haldane type for one dimensional bosons.Comment: 5 pages; 1 eps figure. Revised version, to be published in New. J. Phy

High Order Coherent Control Sequences of Finite-Width Pulses

The performance of sequences of designed pulses of finite length $\tau$ is analyzed for a bath of spins and it is compared with that of sequences of ideal, instantaneous pulses. The degree of the design of the pulse strongly affects the performance of the sequences. Non-equidistant, adapted sequences of pulses, which equal instantaneous ones up to $\mathcal{O}(\tau^3)$, outperform equidistant or concatenated sequences. Moreover, they do so at low energy cost which grows only logarithmically with the number of pulses, in contrast to standard pulses with linear growth.Comment: 6 pages, 5 figures, new figures, published versio

Earthworm diversity in four land use systems in the region of Jaguapitã, Paraná State, Brazil.

Little infonnation is available on earthwonn distribution and diversity in the State of Paraná, southern Brazil, Earthwonn abundanee and species diversity was evaluated in four land use systems near [aguapítã, (Paraná); where pastures are being eonverted to soybean and sugarcane. Samples were taken during the rainy and dry seasons of 2004 and 2005 in eight sites: two old degraded pastures, an old pasture being eonverted to row eropping, two grain erop fields, two sugareane fields and a native forest fragmento Twentyfive 25 x 25 em soil bloeks were taken at eaeh síte, 20 of them to 10 em and five to 30 em depth. Earthwonns were manually sorted from the soil and preserved in fonnaldehyde. Earthwonn species found were: the exotics Pontoscolex corethrurus (Glossoscolecidae), Dichogaster affinis, D. bolaui and D. saliens (Acanthodrí- Iidae), Eukerria saltensis, E. eiseniana and Ocnerodrilus occidentalis (Ocnerodrilídae), and Amynthas sp. (Megascolecidae): the native species Glossoscolex n. sp. and Fimoscolex n. sp. (Glossoscolecidae), Belladrilus n. sp.l and an unidentifiable Oenerodrilidae n, sp.l (probably Belladrílus); and two unidentified Eukerria spp. (of unknown origin) (Oenerodrilidae). Pasture eonversion to row erops had a negative effect on earthwonn abundanee and diversity: fewer individuais and species were found in the eropping systems than the pastures. The forest was not a suitable referenee site, having low earthworm populations and diversity. Exotie species tended to predominate in the land use systems near [aguapítã, but native earthworm species still survived, even in degraded pastures and row erops, many years after deforestation

Temperature-induced shape morphing of bi-metallic structures

In this work, we study the thermo-mechanical behavior of metallic structures designed to significantly change shape in response to thermal stimuli. This behavior is achieved by arranging two metals with different coefficient of thermal expansion (CTE), Aluminum and Titanium, as to create displacement-amplifying units that can expand uniaxially. In particular, our design comprises a low-CTE bar surrounded by a high-CTE frame that features flexure hinges and thicker links. When the temperature increases, the longitudinal expansion of the high-CTE portion is geometrically constrained by the low-CTE bar, resulting in a large tangential displacement. Our design is guided by theoretical models and numerical simulations. We validate our approach by fabricating and characterizing individual units, one dimensional arrays and three-dimensional structures. Our work shows that structurally robust metallic structures can be designed for large shape changes. The results also demonstrate how harsh environmental conditions (e.g., the extreme temperature swings that are characteristic of extraterrestrial environments) can be leveraged to produce function in a fully passive way

The HIE-ISOLDE Superconducting Cavities: Surface Treatment and Niobium Thin Film Coating

CERN has designed and prepared new facilities for the surface treatment and niobium sputter coating of the HIE-ISOLDE superconducting cavities. We describe here the design choices, as well as the results of the first surface treatments and test coatings