Search results for "PLASMA"
showing 10 items of 4043 documents
Robust quantum control by a single-shot shaped pulse
2013
Considering the problem of the control of a two-state quantum system by an external field, we establish a general and versatile method allowing the derivation of smooth pulses which feature the properties of high fidelity, robustness, and low area. Such shaped pulses can be interpreted as a single-shot generalization of the composite pulse-sequence technique with a time-dependent phase.
Hyperfine interaction in the Autler-Townes effect: The formation of bright, dark, and chameleon states
2017
This paper is devoted to clarifying the implications of hyperfine (HF) interaction in the formation of adiabatic (i.e., ``laser-dressed'') states and their expression in the Autler-Townes (AT) spectra. We first use the Morris-Shore model [J. R. Morris and B. W. Shore, Phys. Rev. A 27, 906 (1983)] to illustrate how bright and dark states are formed in a simple reference system where closely spaced energy levels are coupled to a single state with a strong laser field with the respective Rabi frequency ${\mathrm{\ensuremath{\Omega}}}_{S}$. We then expand the simulations to realistic hyperfine level systems in Na atoms for a more general case when non-negligible HF interaction can be treated as…
Study of Mode Competition in the Third Harmonic Gyrotron with Inclusion of the Electron Velocity Spread and the Beam Width
2018
Influence of the electron velocity spread and the beam width on the mode competition and efficiency is investigated in the 1.185- THz third harmonic gyrotron to be used in dynamical nuclear polarization - nuclear magnetic resonance (DNP-NMR) spectrometer.
Teleportation-induced correlated quantum channels.
2009
Quantum teleportation of a n-qubit state performed using as entangled resource a general bipartite state of 2n qubits instead of n Bell states is equivalent to a correlated Pauli channel. This provides a new characterization of such channels in terms of many-body correlation functions of the teleporting media. Our model is then generalized to the Continuous Variable case. We show that this new representation provides a relatively simple method for determining whether a correlated quantum channel is able to reliably convey quantum messages by studying the entanglement properties of the teleportation mediating system.
IBSIMU: a three-dimensional simulation software for charged particle optics.
2010
A general-purpose three-dimensional (3D) simulation code IBSIMU for charged particle optics with space charge is under development at JYFL. The code was originally developed for designing a slit-beam plasma extraction and nanosecond scale chopping for pulsed neutron generator, but has been developed further and has been used for many applications. The code features a nonlinear FDM Poisson's equation solver based on fast stabilized biconjugate gradient method with ILU0 preconditioner for solving electrostatic fields. A generally accepted nonlinear plasma model is used for plasma extraction. Magnetic fields can be imported to the simulations from other programs. The particle trajectories are …
Single trajectory characterization via machine learning
2020
[EN] In order to study transport in complex environments, it is extremely important to determine the physical mechanism underlying diffusion and precisely characterize its nature and parameters. Often, this task is strongly impacted by data consisting of trajectories with short length (either due to brief recordings or previous trajectory segmentation) and limited localization precision. In this paper, we propose a machine learning method based on a random forest architecture, which is able to associate single trajectories to the underlying diffusion mechanism with high accuracy. In addition, the algorithm is able to determine the anomalous exponent with a small error, thus inherently provi…
Ground states of ultrasoft particles with attractions: a genetic algorithm approach
2009
International audience; We analyze in detail the ground-state structure of model systems of athermal star polymers with an additional, tunable attraction that may result from dispersion or depletion forces. To perform a free, unbiased search in the space spanned by the crystal parameters, we employ genetic algorithms, which are enhanced with respect to previous versions in their ability to find stable structures that occupy very narrow basins of attraction in the energy landscape. Application of this method brings about a very large variety of ground states for star polymers with attractions, in particular for the case of intermediate functionalities and strong, short-range attractive force…
Absorbing anisotropic and gyrotropic slab between crossed polarizers in parallel light
1980
When a birefringent slab is rotated between two crossed polarizers, the four maxima and four minima of the transmitted intensity occur, as known, at every π/4 radians. If the slab is also optically active, the maxima and minima are arranged in other patterns that may be grouped according to the number of extrema met in one complete turn of the slab: four or eight. All the possible patterns are classified and each is related to some peculiarity of the complex refractive index of the slab.
Thermodynamic Approach to the Self-Diffusiophoresis of Colloidal Janus Particles
2019
Most available theoretical predictions for the self-diffusiophoretic motion of colloidal particles are based on the hydrodynamic thin boundary layer approximation in combination with a solvent body force due to a self-generated local solute gradient. This gradient is enforced through specifying boundary conditions, typically without accounting for the thermodynamic cost to maintain the gradient. Here, we present an alternative thermodynamic approach that exploits a direct link between dynamics and entropy production: the local detailed balance condition. We study two cases: First, we revisit self-propulsion in a demixing binary solvent. At variance with a slip velocity, we find that propuls…
Drude weight increase by orbital and repulsive interactions in fermionic ladders
2019
In strictly one-dimensional systems, repulsive interactions tend to reduce particle mobility on a lattice. Therefore, the Drude weight, controlling the divergence at zero-frequency of optical conductivities in perfect conductors, is lower than in non-interacting cases. We show that this is not the case when extending to quasi one-dimensional ladder systems. Relying on bosonization, perturbative and matrix product states (MPS) calculations, we show that nearest-neighbor interactions and magnetic fluxes provide a bias between back- and forward-scattering processes, leading to linear corrections to the Drude weight in the interaction strength. As a consequence, Drude weights counter-intuitivel…