Local Invariants and Pairwise Entanglement in Symmetric Multi-qubit System

Pairwise entanglement properties of a symmetric multi-qubit system are analyzed through a complete set of two-qubit local invariants. Collective features of entanglement, such as spin squeezing, are expressed in terms of invariants and a classifcation scheme for pairwise entanglement is proposed. The invariant criteria given here are shown to be related to the recently proposed (Phys. Rev. Lett. 95, 120502 (2005)) generalized spin squeezing inequalities for pairwise entanglement in symmetric multi-qubit states.Comment: 9 pages, 2 figures, REVTEX, Replaced with a published versio

Generalized small-signal modelling of dual active bridge DC/DC converter

this paper presents a novel generalised approach of the small-signal modelling of dual active bridge (DAB) DC/DC converter. The adopted analysis is based on a per-unit fundamental frequency representation of the DAB. The outcome of the proposed modelling approach is a small signal, linearised, state-space DAB model; which is considered as a main building block for future control applications. The developed small signal DAB model includes all possible degrees of freedom affecting the performance of the DAB; this includes the voltage conversion ratio to allow the study of all DAB operation modes (i.e.: unity-gain and buck/boost modes.). Furthermore, since triple phase shift control (TPS) is used in this development work, the proposed model incorporates phase shift in addition to duty ratios. This feature allows for bridge voltage regulation, which is essential for efficient DAB operation in the case of buck/boost operation. Another key achievement is that the proposed small signal modelling methodology can be applied to any bidirectional DC-DC converter regardless of ratings, parameter values and number of ports. Extensive simulation is carried out to verify the proposed analysis

Collective multipole-like signatures of entanglement in symmetric N-qubit systems

A cogent theory of collective multipole-like quantum correlations in symmetric multiqubit states is presented by employing SO(3) irreducible spherical tensor representation. An arbitrary bipartite division of this system leads to a family of inequalities to detect entanglement involving averages of these tensors expressed in terms of the total system angular momentum operator. Implications of this theory to the quantum nature of multipole-like correlations of all orders in the Dicke states are deduced. A selected set of examples illustrate these collective tests. Such tests detect entanglement in macroscopic atomic ensembles, where individual atoms are not accessible.Comment: REVTEX, 4 pages with 1 figure; To appear in Phys. Rev.

Adubação orgânica no arroz de terras altas: relacionamentos entre brusone, esterilidade de espiguetas e produtividade.

O trabalho foi conduzido adotando-se o Sistema Plantio Direto, na Embrapa Arroz e Feijão, Fazenda Capivara, no município de Santo Antônio de Goiás, GO. Foram avaliados, no ano agrícola 2001/02, os efeitos residuais de cinco tratamentos de adubação orgânica, de um experimento realizado em 2000/01, sob Sistema Plantio Convencional.bitstream/CNPAF/19924/1/comt_42.pd

Aplicação de silicato de cálcio na cultura do arroz.

Na Embrapa Arroz e Feijão, as pesquisa sobre utilização de silicato de cálcio em arroz foram iniciadas em 1995. Apesar de recentes, as pesquisas tem obtido resultados extremamente interessantes do efeito do silicato de cálcio, tanto no aumento de rendimento de grãos e incidência de doenças, quanto na melhoria da fertilidade do solo e como condicionador de condições quimicamente favoráveis ao desenvolvimento das plantas.bitstream/CNPAF/19678/1/circ_51.pd

Non-local properties of a symmetric two-qubit system

Non-local properties of symmetric two-qubit states are quantified in terms of a complete set of entanglement invariants. We prove that negative values of some of the invariants are signatures of quantum entanglement. This leads us to identify sufficient conditions for non-separability in terms of entanglement invariants. Non-local properties of two-qubit states extracted from (i) Dicke state (ii) state generated by one-axis twisting Hamiltonian, and (iii) one-dimensional Ising chain with nearest neighbour interaction are analyzed in terms of the invariants characterizing them.Comment: 5 pages, no figure

Theory of Suspension Segregation in Partially Filled Horizontal Rotating Cylinders

It is shown that a suspension of particles in a partially-filled, horizontal, rotating cylinder is linearly unstable towards axial segregation and an undulation of the free surface at large enough particle concentrations. Relying on the shear-induced diffusion of particles, concentration-dependent viscosity, and the existence of a free surface, our theory provides an explanation of the experiments of Tirumkudulu et al., Phys. Fluids 11, 507-509 (1999); ibid. 12, 1615 (2000).Comment: Accepted for publication in Phys Fluids (Lett) 10 pages, two eps figure