5,121 research outputs found
Macroscopic quantum jumps and entangled state preparation
Recently we predicted a random blinking, i.e. macroscopic quantum jumps, in
the fluorescence of a laser-driven atom-cavity system [Metz et al., Phys. Rev.
Lett. 97, 040503 (2006)]. Here we analyse the dynamics underlying this effect
in detail and show its robustness against parameter fluctuations. Whenever the
fluorescence of the system stops, a macroscopic dark period occurs and the
atoms are shelved in a maximally entangled ground state. The described setup
can therefore be used for the controlled generation of entanglement. Finite
photon detector efficiencies do not affect the success rate of the state
preparation, which is triggered upon the observation of a macroscopic
fluorescence signal. High fidelities can be achieved even in the vicinity of
the bad cavity limit due to the inherent role of dissipation in the jump
process.Comment: 14 pages, 12 figures, proof of the robustness of the state
preparation against parameter fluctuations added, figure replace
Structure analysis of the virtual Compton scattering amplitude at low energies
We analyze virtual Compton scattering off the nucleon at low energies in a
covariant, model-independent formalism.
We define a set of invariant functions which, once the irregular nucleon pole
terms have been subtracted in a gauge-invariant fashion, is free of poles and
kinematical zeros.
The covariant treatment naturally allows one to implement the constraints due
to Lorentz and gauge invariance, crossing symmetry, and the discrete
symmetries.
In particular, when applied to the reaction,
charge-conjugation symmetry in combination with nucleon crossing generates four
relations among the ten originally proposed generalized polarizabilities of the
nucleon.Comment: 19 pages, LaTeX2e/RevTeX, no figures, original sections IV.-VI.
removed, to be discussed in a separate publication, none of the conclusions
change
Reactive transport modelling of the long-term interaction between carbon steel and MX-80 bentonite at 25 °C
The geological disposal in deep bedrock repositories is the preferred option for the management of high-level radioactive waste (HLW). In some of these concepts, carbon steel is considered as a potential canister material and bentonites are planned as backfill material to protect metallic waste containers. Therefore, a 1D radial reactive transport model has been developed in order to better understand the processes occurring during the long-term iron-bentonite interaction. The numerical model accounts for diffusion, aqueous complexation reactions, mineral dissolution/precipitation and cation exchange at a constant temperature of 25 °C under anoxic conditions. Our results suggest that Fe is sorbed at the montmorillonite surface via cation exchange in the short-term, and it is consumed by formation of the secondary phases in the long-term. The numerical model predicts precipitation of nontronite, magnetite and greenalite as corrosion products. Calcite precipitates due to cation exchange in the short-term and due to montmorillonite dissolution in the long-term. Results further reveal a significant increase in pH in the long-term, while dissolution/precipitation reactions result in limited variations of the porosity. A sensitivity analysis has also been performed to test the effect of selected parameters, such as corrosion rate, diffusion coefficient and composition of the bentonite porewater, on the corrosion processes. Overall, outcomes suggest that the predicted main corrosion products in the long-term are Fe-silicate minerals, such phases thus should deserve further attention as a chemical barrier in the diffusion of radionuclides to the repository far field
Low-energy and low-momentum representation of the virtual Compton scattering amplitude
We perform an expansion of the virtual Compton scattering amplitude for low
energies and low momenta and show that this expansion covers the transition
from the regime to be investigated in the scheduled photon electroproduction
experiments to the real Compton scattering regime.
We discuss the relation of the generalized polarizabilities of virtual
Compton scattering to the polarizabilities of real Compton scattering.Comment: 13 pages, LaTeX2e/RevTeX, no figure
Identification of phospholipid as an essential part of bovine vitamin K-dependent carboxylase
Solubility and TRLFS study of Nd(III) and Cm(III) in dilute to concentrated alkaline NaCl-NaNO₃ and MgCl₂-Mg(NO₃)₂ solutions
Production of entanglement in Raman three-level systems using feedback
We examine the theoretical limits of the generation of entanglement in a
damped coupled ion-cavity system using jump-based feedback. Using Raman
transitions to produce entanglement between ground states reduces the necessary
feedback bandwidth, but does not improve the overall effect of the spontaneous
emission on the final entanglement. We find that the fidelity of the resulting
entanglement will be limited by the asymmetries produced by vibrations in the
trap, but that the concurrence remains above 0.88 for realistic ion trap sizes.Comment: 8 pages, 8 figure
Evolutionary Dynamics on Small-Order Graphs
Abstract. We study the stochastic birth-death model for structured finite populations popularized by Lieberman et al. [Lieberman, E., Hauert, C., Nowak, M.A., 2005. Evolutionary dynamics on graphs. Nature 433, 312-316]. We consider all possible connected undirected graphs of orders three through eight. For each graph, using the Monte Carlo Markov Chain simulations, we determine the fixation probability of a mutant introduced at every possible vertex. We show that the fixation probability depends on the vertex and on the graph. A randomly placed mutant has the highest chances of fixation in a star graph, closely followed by star-like graphs. The fixation probability was lowest for regular and almost regular graphs. We also find that within a fixed graph, the fixation probability of a mutant has a negative correlation with the degree of the starting vertex. 1
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