792 research outputs found
Effects of relative phase and interactions on atom-laser outcoupling from a double-well Bose-Einstein condensate: Markovian and non-Markovian dynamics
We investigate aspects of the dynamics of a continuous atom-laser scheme
based on the merging of independently formed atomic condensates. Our
theoretical analysis covers the Markovian as well as the non-Markovian
operational regimes, and is based on a semiclassical (mean-field) two-mode
model. The role of the relative phase between the two condensates and the
effect of interatomic interactions on the evolution of the trapped populations
and the distribution of outcoupled atoms are discussed.Comment: to appear in J. Phys.
Entanglement trapping in a non-stationary structured reservoir
We study a single two-level atom interacting with a reservoir of modes
defined by a reservoir structure function with a frequency gap. Using the
pseudomodes technique, we derive the main features of a trapping state formed
in the weak coupling regime. Utilising different entanglement measures we show
that strong correlations and entanglement between the atom and the modes are in
existence when this state is formed. Furthermore, an unexpected feature for the
reservoir is revealed. In the long time limit and for weak coupling the
reservoir spectrum is not constant in time.Comment: 10 pages, 16 figure
Adiabatic cavity QED with pairs of atoms: Atomic entanglement and Quantum teleportation
We study the dynamics of a pair of atoms, resonantly interacting with a
single mode cavity, in the situation where the atoms enter the cavity with a
time delay between them. Using time dependent coupling functions to represent
the spatial profile of the mode, we considered the adiabatic limit of the
system. Although the time evolution is mostly adiabatic, energy crossings play
an important role in the system dynamics. Following from this, entanglement,
and a procedure for cavity state teleportation are considered. We examine the
behaviour of the system when we introduce decoherence, a finite detuning, and
potential asymmetries in the coupling profiles of the atoms.Comment: 12 pages, 7 figures, To appear in European Physical Journal Special
Topic
Entanglement in the adiabatic limit of a two-atom Tavis-Cummings model
We study the adiabatic limit for the sequential passage of atoms through a
high-Q cavity, in the presence of frequency chirps. Despite the fact that the
adiabatic approximation might be expected to fail, we were able to show that
for proper choice of Stark-pulses this is not the case. Instead, a connection
to the resonant limit is established, where the robust creation of entanglement
is demonstrated. Recent developments in the fabrication of high-Q cavities
allow fidelities for a maximally entangled state up to 97%.Comment: 12 pages, 5 figures, Submitted to Physica Scripta as part of the
Proceedings of the 15th CEWQO 200
Tensor feature hallucination for few-shot learning
Few-shot learning addresses the challenge of learning how to address novel tasks given not just limited supervision but limited data as well. An attractive solution is synthetic data generation. However, most such methods are overly sophisticated, focusing on high-quality, realistic data in the input space. It is unclear whether adapting them to the few-shot regime and using them for the downstream task of classification is the right approach. Previous works on synthetic data generation for few-shot classification focus on exploiting complex models, e.g. a Wasserstein GAN with multiple regularizers or a network that transfers latent diversities from known to novel classes.We follow a different approach and investigate how a simple and straightforward synthetic data generation method can be used effectively. We make two contributions, namely we show that: (1) using a simple loss function is more than enough for training a feature generator in the few-shot setting; and (2) learning to generate tensor features instead of vector features is superior. Extensive experiments on miniImagenet, CUB and CIFAR-FS datasets show that our method sets a new state of the art, outperforming more sophisticated few-shot data augmentation methods. The source code can be found at https://github.com/MichalisLazarou/TFH_fewshot
Molecular heat pump for rotational states
In this work we investigate the theory for three different uni-directional
population transfer schemes in trapped multilevel systems which can be utilized
to cool molecular ions. The approach we use exploits the laser-induced coupling
between the internal and motional degrees of freedom so that the internal state
of a molecule can be mapped onto the motion of that molecule in an external
trapping potential. By sympathetically cooling the translational motion back
into its ground state the mapping process can be employed as part of a cooling
scheme for molecular rotational levels. This step is achieved through a common
mode involving a laser-cooled atom trapped alongside the molecule. For the
coherent mapping we will focus on adiabatic passage techniques which may be
expected to provide robust and efficient population transfers. By applying
far-detuned chirped adiabatic rapid passage pulses we are able to achieve an
efficiency of better than 98% for realistic parameters and including
spontaneous emission. Even though our main focus is on cooling molecular
states, the analysis of the different adiabatic methods has general features
which can be applied to atomic systems
The genetics of immune and infection phenotypes in wild mice, Mus musculus domesticus
Wild animals are under constant threat from a wide range of micro- and macroparasites in their environment. Animals make immune responses against parasites, and these are important in affecting the dynamics of parasite populations. Individual animals vary in their anti-parasite immune responses. Genetic polymorphism of immune-related loci contributes to inter-individual differences in immune responses, but most of what we know in this regard comes from studies of humans or laboratory animals; there are very few such studies of wild animals naturally infected with parasites. Here we have investigated the effect of single nucleotide polymorphisms (SNPs) in immune-related loci (the major histocompatibility complex [MHC], and loci coding for cytokines and Toll-like receptors) on a wide range of immune and infection phenotypes in UK wild house mice, Mus musculus domesticus. We found strong associations between SNPs in various MHC and cytokine-coding loci on both immune measures (antibody concentration and cytokine production) and on infection phenotypes (infection with mites, worms and viruses). Our study provides a comprehensive view of how polymorphism of immune-related loci affects immune and infection phenotypes in naturally infected wild rodent populations
Dephasing effects on stimulated Raman adiabatic passage in tripod configurations
We present an analytic description of the effects of dephasing processes on
stimulated Raman adiabatic passage in a tripod quantum system. To this end, we
develop an effective two-level model. Our analysis makes use of the adiabatic
approximation in the weak dephasing regime. An effective master equation for a
two-level system formed by two dark states is derived, where analytic solutions
are obtained by utilizing the Demkov-Kunike model. From these, it is found that
the fidelity for the final coherent superposition state decreases exponentially
for increasing dephasing rates. Depending on the pulse ordering and for
adiabatic evolution the pulse delay can have an inverse effect.Comment: 13 pages; 9 figures; Accepted for publication Physical Review
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A new framework architecture for next generation e-Health services
The challenge for fast and low-cost deployment of ubiquitous personalized e-Health services has prompted us to propose a new framework architecture for such services. We have studied the operational features and the environment of e-Health services and we led to a framework structure that extends the ETSI/Parlay architecture, which is used for the deployment of standardized services over the next generation IP networks. We expanded the ETSI/Parlay architecture with new service capability features as well as sensor, profiling and security mechanisms. The proposed framework assists the seamless integration, within the e-Health service structure, of diverse facilities provided by both the underlying communication and computing infrastructure as well as the patient's bio and context sensor networks. Finally, we demonstrate the deployment of a tele-monitoring service in smart home environment based on the proposed framework architecture
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