Quantum computing with incoherent resources and quantum jumps

Spontaneous emission and the inelastic scattering of photons are two natural processes usually associated with decoherence and the reduction in the capacity to process quantum information. Here we show that when suitably detected, these photons are sufficient to build all the fundamental blocks needed to perform quantum computation in the emitting qubits while protecting them from deleterious dissipative effects. We exemplify by showing how to teleport an unknown quantum state and how to efficiently prepare graph states for the implementation of measurement-based quantum computation.Comment: 5 pages, 5 figure

The Geometry of Entanglement Sudden Death

In open quantum systems, entanglement can vanish faster than coherence. This phenomenon is usually called sudden death of entanglement. In this paper sudden death of entanglement is discussed from a geometrical point of view, in the context of two qubits. A classification of possible scenarios is presented, with important known examples classified. Theoretical and experimental construction of other examples is suggested as well as large dimensional and multipartite versions of the effect.Comment: 6 pages, 2 figures, references added, initial paragraph corrected, sectioning adopted, some parts rewritten; accepted by New J. Phy

New foliose and gelatinous red macroalgae (Rhodophycota) from the Azores: morphological and geographical observations.

Copyright © 2002 Published by Elsevier Science B.V.The following four species of foliose and gelatinous red algae (Rhodophycota) are newly recorded for the Azores archipelago (North Atlantic Ocean): Gracilaria multipartita (Clemente) Harvey, Meristotheca decumbens Grunow (Solieriaceae), Asteromenia peltata (W.R. Taylor) Huisman and A.J.K. Millar (Rhodymeniaceae), and Agardhinula browneae (J. Agardh) De Toni (Faucheaceae). The species are described, and information on reproductive status, ecology and biogeographical relationships is provided

Asymptotic Entanglement Dynamics and Geometry of Quantum States

A given dynamics for a composite quantum system can exhibit several distinct properties for the asymptotic entanglement behavior, like entanglement sudden death, asymptotic death of entanglement, sudden birth of entanglement, etc. A classification of the possible situations was given in [M. O. Terra Cunha, {\emph{New J. Phys}} {\bf{9}}, 237 (2007)] but for some classes there were no known examples. In this work we give a better classification for the possibile relaxing dynamics at the light of the geometry of their set of asymptotic states and give explicit examples for all the classes. Although the classification is completely general, in the search of examples it is sufficient to use two qubits with dynamics given by differential equations in Lindblad form (some of them non-autonomous). We also investigate, in each case, the probabilities to find each possible behavior for random initial states.Comment: 9 pages, 2 figures; revised version accepted for publication in J. Phys. A: Math. Theo

A Hybridized Approach to Validation: The Role of Sociological Research Methods in Pedestrian Modeling

Pedestrian and crowd-movement models are difficult to validate using traditional empirical methods because of data-related issues such as generalizability, collection ethics, and costs. Commonly used validation methods make strong assumptions about emergence and the importance of crowd structure, leaving a gap in validation literature. The paper reviews the most common methods of validating pedestrian models and proposes a hybridized qualitative approach to validating models that covers more complex group dynamics and possible situations of panic