3,688 research outputs found
Towards Lattice Quantum Chromodynamics on FPGA devices
In this paper we describe a single-node, double precision Field Programmable
Gate Array (FPGA) implementation of the Conjugate Gradient algorithm in the
context of Lattice Quantum Chromodynamics. As a benchmark of our proposal we
invert numerically the Dirac-Wilson operator on a 4-dimensional grid on three
Xilinx hardware solutions: Zynq Ultrascale+ evaluation board, the Alveo U250
accelerator and the largest device available on the market, the VU13P device.
In our implementation we separate software/hardware parts in such a way that
the entire multiplication by the Dirac operator is performed in hardware, and
the rest of the algorithm runs on the host. We find out that the FPGA
implementation can offer a performance comparable with that obtained using
current CPU or Intel's many core Xeon Phi accelerators. A possible multiple
node FPGA-based system is discussed and we argue that power-efficient High
Performance Computing (HPC) systems can be implemented using FPGA devices only.Comment: 17 pages, 4 figure
Tuning and Switching a Plasmonic Quantum Dot Sandwich in a Nematic Line Defect
We study the quantum-mechanical effects arising in a single semiconductor
core/shell quantum dot controllably sandwiched between two plasmonic nanorods.
Control over the position and the sandwich confinement structure is achieved by
the use of a linear-trap, liquid-crystal line defect and laser tweezers that
push the sandwich together. This arrangement allows for the study of exciton
plasmon interactions in a single structure, unaltered by ensemble effects or
the complexity of dielectric interfaces. We demonstrate the effect of plasmonic
confinement on the photon-antibunching behavior of the quantum dot and its
luminescence lifetime. The quantum dot behaves as a single emitter when
nanorods are far away from the quantum dot but shows possible multiexciton
emission and a significantly decreased lifetime when tightly confined in a
plasmonic sandwich. These findings demonstrate that liquid crystal defects,
combined with laser tweezers, enable a versatile platform to study plasmonic
coupling phenomena in a nanoscale laboratory, where all elements can be
arranged almost at will.Comment: Supporting information at the en
Key Generation in Wireless Sensor Networks Based on Frequency-selective Channels - Design, Implementation, and Analysis
Key management in wireless sensor networks faces several new challenges. The
scale, resource limitations, and new threats such as node capture necessitate
the use of an on-line key generation by the nodes themselves. However, the cost
of such schemes is high since their secrecy is based on computational
complexity. Recently, several research contributions justified that the
wireless channel itself can be used to generate information-theoretic secure
keys. By exchanging sampling messages during movement, a bit string can be
derived that is only known to the involved entities. Yet, movement is not the
only possibility to generate randomness. The channel response is also strongly
dependent on the frequency of the transmitted signal. In our work, we introduce
a protocol for key generation based on the frequency-selectivity of channel
fading. The practical advantage of this approach is that we do not require node
movement. Thus, the frequent case of a sensor network with static motes is
supported. Furthermore, the error correction property of the protocol mitigates
the effects of measurement errors and other temporal effects, giving rise to an
agreement rate of over 97%. We show the applicability of our protocol by
implementing it on MICAz motes, and evaluate its robustness and secrecy through
experiments and analysis.Comment: Submitted to IEEE Transactions on Dependable and Secure Computin
Workshops at IMS2023
Lists future events that should be of interest to practitioners and researchers.Peer ReviewedPostprint (published version
Out of equilibrium dynamics of classical and quantum complex systems
Equilibrium is a rather ideal situation, the exception rather than the rule
in Nature. Whenever the external or internal parameters of a physical system
are varied its subsequent relaxation to equilibrium may be either impossible or
take very long times. From the point of view of fundamental physics no generic
principle such as the ones of thermodynamics allows us to fully understand
their behaviour. The alternative is to treat each case separately. It is
illusionary to attempt to give, at least at this stage, a complete description
of all non-equilibrium situations. Still, one can try to identify and
characterise some concrete but still general features of a class of out of
equilibrium problems - yet to be identified - and search for a unified
description of these. In this report I briefly describe the behaviour and
theory of a set of non-equilibrium systems and I try to highlight common
features and some general laws that have emerged in recent years.Comment: 36 pages, to be published in Compte Rendus de l'Academie de Sciences,
T. Giamarchi e
The Abrikosov vortex structure revealed through near-field radiative heat exchange
One of the signatures of superconductivity is the formation of the Abrikosov
vortex lattice in type-II superconductors in the presence of an external
magnetic field. Here, we study the near-field radiative heat transfer between a
spherical nanoparticle and a nearby planar substrate, both made of
optimally-doped YBaCuO. We show that the heat flux
displays a periodic spatial pattern congruent with the material optical
response modulated by the Abrikosov lattice. Our results enrich the toolbox of
methods available to study non-conventional superconductivity.Comment: 3 figures, Supplementary material availabl
HIRIS (High-Resolution Imaging Spectrometer: Science opportunities for the 1990s. Earth observing system. Volume 2C: Instrument panel report
The high-resolution imaging spectrometer (HIRIS) is an Earth Observing System (EOS) sensor developed for high spatial and spectral resolution. It can acquire more information in the 0.4 to 2.5 micrometer spectral region than any other sensor yet envisioned. Its capability for critical sampling at high spatial resolution makes it an ideal complement to the MODIS (moderate-resolution imaging spectrometer) and HMMR (high-resolution multifrequency microwave radiometer), lower resolution sensors designed for repetitive coverage. With HIRIS it is possible to observe transient processes in a multistage remote sensing strategy for Earth observations on a global scale. The objectives, science requirements, and current sensor design of the HIRIS are discussed along with the synergism of the sensor with other EOS instruments and data handling and processing requirements
Semiconductor Nanocrystal Building Blocks for Solar Applications: Synthesis, Self-Assembly, and Film Characterization
Semiconductor nanocrystals have emerged as promising materials for light harvesting and production of electrical energy. Their unique optical properties and solution processibility suggest that they can be utilized in new ways to build on the knowledge base existing from the study of bulk semiconductors. Here, CuInSe2, CdTe, and CdSe are discussed. Synthetic control of size, shape, crystal structure, and elemental composition are crucial to realizing the potential of these nanoscale building blocks. In this work, new methods for colloidal synthesis of semiconducting nanocrystals are presented. As a consequence, the improved control over structure makes it possible to self-assemble them into oriented and multicomponent films. This provides a route for the future to pattern nanoscale structure into solar cell active layers from the bottom up
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