Physical interpretation of the Wigner rotations and its implications for relativistic quantum information

We present a new treatment for the spin of a massive relativistic particle in the context of quantum information based on a physical interpretation of the Wigner rotations, obtaining different results in relation to the previous works. We are lead to the conclusions that it is not possible to define a reduced density matrix for the particle spin and that the Pauli-Lubanski (or similar) spin operators are not suitable to describe measurements where spin couples to an electromagnetic field in the measuring apparatus. These conclusions contradict the assumptions made by most of the previous papers on the subject. We also propose an experimental test of our formulation.Comment: 10 pages, 2 figures. Several changes were made on the text. One extra example was include

Ozone against mycotoxins and pesticide residues in food: Current applications and perspectives

Food safety may be compromised by the presence of chemical contaminants, such as mycotoxins and pesticide residues. Mycotoxins are natural contaminants produced by certain species of filamentous fungi and can cause toxic effects on human health. Pesticide residues are any specified substance in food resulting from the use of a pesticide with toxicological significance. To protect consumers from these toxic substances, different food regulatory agencies have set maximum levels permitted in different raw materials and processed foods. However, recent research has demonstrated a high incidence of both mycotoxins and pesticide residues (not simultaneously) in foods marketed all around the world, sometimes with levels above the regulated limits. One way to reduce such contaminants is to use ozone (O3) in food processing. Due to its high potential as an oxidant, O3 or the radicals generated in the ozonation process react with mycotoxins and pesticide residues that lose their toxicity due to molecular degradation. In this review paper the recent research into using O3 for gaseous ozonation and ozonized water to decontaminate food by eliminating and/or reducing mycotoxins and pesticide residues are discussed. Also the changes promoted in food quality attributes, the possible formation of degradation products of toxic relevance, as well as some perspectives for the future use of this technology in food processing are explored.National Counsel of Technological and Scientific Development, BrazilCoordenação de Aperfeiçoamento de Pessoal de Nível Superior, BrazilRio de Janeiro State Foundation to Support ResearchAuthors are grateful for the financial support provided by CNPq (National Counsel of Technological and Scientific Development, Brazil), CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil) and FAPERJ (Rio de Janeiro State Foundation to Support Research)

Geometrically induced singular behavior of entanglement

We show that the geometry of the set of quantum states plays a crucial role in the behavior of entanglement in different physical systems. More specifically it is shown that singular points at the border of the set of unentangled states appear as singularities in the dynamics of entanglement of smoothly varying quantum states. We illustrate this result by implementing a photonic parametric down conversion experiment. Moreover, this effect is connected to recently discovered singularities in condensed matter models.Comment: v2: 4 pags, 4 figs. A discussion before the proof of Proposition 1 and tomographic results were included, Propostion 2 was removed and the references were fixe