29 research outputs found
On the effective Dirac dynamics of ultracold atoms in bichromatic optical lattices
We study the dynamics of ultracold atoms in tailored bichromatic optical
lattices. By tuning the lattice parameters, one can readily engineer the band
structure and realize a Dirac point, i.e. a true crossing of two Bloch bands.
The dynamics in the vicinity of such a crossing is described by the
one-dimensional Dirac equation, which is rigorously shown beyond the
tight-binding approximation. Within this framework we analyze the effects of an
external potential and demonstrate numerically that it is possible to
demonstrate Klein tunneling with current experimental setups.Comment: 6 pages, 5 figure
Doppler-free frequency modulation spectroscopy of atomic erbium in a hollow cathode discharge cell
The erbium atomic system is a promising candidate for an atomic Bose-Einstein
condensate of atoms with a non-vanishing orbital angular momentum ()
of the electronic ground state. In this paper we report on the frequency
stabilization of a blue external cavity diode laser system on the 400.91
laser cooling transition of atomic erbium. Doppler-free saturation spectroscopy
is applied within a hollow cathode discharge tube to the corresponding
electronic transition of several of the erbium isotopes. Using the technique of
frequency modulation spectroscopy, a zero-crossing error signal is produced to
lock the diode laser frequency on the atomic erbium resonance. The latter is
taken as a reference laser to which a second main laser system, used for laser
cooling of atomic erbium, is frequency stabilized
Relativistic quantum mechanics with trapped ions
We consider the quantum simulation of relativistic quantum mechanics, as
described by the Dirac equation and classical potentials, in trapped-ion
systems. We concentrate on three problems of growing complexity. First, we
study the bidimensional relativistic scattering of single Dirac particles by a
linear potential. Furthermore, we explore the case of a Dirac particle in a
magnetic field and its topological properties. Finally, we analyze the problem
of two Dirac particles that are coupled by a controllable and confining
potential. The latter interaction may be useful to study important phenomena as
the confinement and asymptotic freedom of quarks.Comment: 17 pages, 4 figure
Quantum transport in ultracold atoms
Ultracold atoms confined by engineered magnetic or optical potentials are
ideal systems for studying phenomena otherwise difficult to realize or probe in
the solid state because their atomic interaction strength, number of species,
density, and geometry can be independently controlled. This review focuses on
quantum transport phenomena in atomic gases that mirror and oftentimes either
better elucidate or show fundamental differences with those observed in
mesoscopic and nanoscopic systems. We discuss significant progress in
performing transport experiments in atomic gases, contrast similarities and
differences between transport in cold atoms and in condensed matter systems,
and survey inspiring theoretical predictions that are difficult to verify in
conventional setups. These results further demonstrate the versatility offered
by atomic systems in the study of nonequilibrium phenomena and their promise
for novel applications.Comment: 24 pages, 7 figures. A revie
Feedback from the Fifth European Bioanalysis Forum Young Scientist Symposium
Since 2014, the European Bioanalysis Forum (EBF) organizes a Young Scientist Symposium. The meeting format was created to provide development opportunities for young scientists to engage in international discussions. Creating a peer community of young scientists has been a proven recipe to lower the threshold and promote engagement in this community of young talents. At the same time, the meetings are aimed at stimulating collaboration between the EBF and academia. This manuscript summarizes the discussions at the Fifth EBF Young Scientist Symposium, held in Bologna (Italy) between 20 and 21 March 2019
Enhanced biodiversity of gut flora and feed efficiency in pond cultured tilapia under reduced frequency feeding strategies.
Feed constitutes 50-70% of total production costs of tilapia, one of the most widely cultured finfishes in the world. We evaluated reduced-feeding strategies for improving production efficiency of Nile tilapia (Oreochromis niloticus). In a 12-week pond trial, fish were fed daily, every other day, every third day, or not at all. Ponds were fertilized to enhance natural foods. In a fifth group fish were fed daily without pond fertilization. Fish fed daily with or without pond fertilization and fish fed every other day had higher specific growth rates, survivability, and net production than the other two treatments. Fish feed efficiency and benefit to cost ratio was highest for treatments fed in a pulsatile manner (i.e. fed every other day or every third day) with fish fed on alternate days providing the best net return among all groups. Fish fed on alternate days had more moderate gene expression levels of intestinal nutrient transporters which may allow for a more balanced and efficient nutrient uptake. Fecal microbe analyses identified 145 families of prokaryotic and 132 genera of eukaryotic organisms in tilapia. The highest diversity of prokaryotes was found in fish fed either every other day or daily in fertilized ponds and the highest diversity of eukaryotes was found in fish fed every other day. These studies indicate feeding Nile tilapia on alternate days along with weekly pond fertilization has no deleterious effects on growth, survivability, or production versus daily feeding regimes, but enhances feed efficiency by 76% and provides the greatest net return on investments. Our studies also suggest for the first time that combining alternate-day feeding with pond fertilization produces the greatest microbial biodiversity in the intestine that could contribute to enhanced feed efficiency and overall health of tilapia
Engineering of Landau-Zener tunneling
Several ways are discussed how to control the Landau-Zener tunneling in the
Wannier-Stark system. We focus on a realization of this system with interacting
and noninteracting ultracold bosons. The tunneling from the ground band to the
continuum is shown to depend crucially on the initial condition and system
parameters and, more interestingly, on added timedependent disorder -- noise --
on the lattice beams