2,956 research outputs found
Coherence properties of coupled optomechanical cavities
In this work we investigate an optomechanical system consisting of two
cavities coupled to the same mechanical resonator. We consider each cavity
being weakly pumped as well as a small tunneling rate between the cavities. In
such conditions, the system can be studied via quantum Langevin equations and
the steady state solution can be found perturbatively. In order to ensure that
the approximations and methods used to study the system are suitable, the
analytical results were compared to numerical simulations. We study the
statistical properties of the cavity radiation fields and we show that
depending on the values of the parameters of the system, it is possible to
modify the spectrum of the cavities and even enhance the sub-Poissonian
character of the cavity field.Comment: 8 pages, 6 figure
Improved limit on electron neutrino charge radius through a new evaluation of the weak mixing angle
We have obtained a new limit on the electron neutrino effective charge radius
from a new evaluation of the weak mixing angle by a combined fit of all
electron-(anti)neutrino electron elastic scattering measurements. Weak mixing
angle is found to be sin^2 theta_W=0.259 \pm 0.025 in the low energy regime
below 100 MeV. The electron neutrino charge radius squared is bounded to be in
the range -0.13 10^-32 cm^2 < r^2 < 3.32 10^-32 cm^2 at 90 % C.L. Both results
improve previously published analyses. We also discuss perspectives of future
experiments to improve these constraints.Comment: 10 pages, 2 figures. Final published versio
An AER handshake-less modular infrastructure PCB with x8 2.5Gbps LVDS serial links
Nowadays spike-based brain processing emulation is
taking off. Several EU and others worldwide projects are
demonstrating this, like SpiNNaker, BrainScaleS, FACETS, or
NeuroGrid. The larger the brain process emulation on silicon is,
the higher the communication performance of the hosting
platforms has to be. Many times the bottleneck of these system
implementations is not on the performance inside a chip or a
board, but in the communication between boards. This paper
describes a novel modular Address-Event-Representation (AER)
FPGA-based (Spartan6) infrastructure PCB (the AER-Node
board) with 2.5Gbps LVDS high speed serial links over SATA
cables that offers a peak performance of 32-bit 62.5Meps (Mega
events per second) on board-to-board communications. The
board allows back compatibility with parallel AER devices
supporting up to x2 28-bit parallel data with asynchronous
handshake. These boards also allow modular expansion
functionality through several daughter boards. The paper is
focused on describing in detail the LVDS serial interface and
presenting its performance.Ministerio de Ciencia e Innovación TEC2009-10639-C04-02/01Ministerio de Economía y Competitividad TEC2012-37868-C04-02/01Junta de Andalucía TIC-6091Ministerio de Economía y Competitividad PRI-PIMCHI-2011-076
Live Demonstration: Multiplexing AER Asynchronous Channels over LVDS Links with Flow-Control and Clock- Correction for Scalable Neuromorphic Systems
In this live demonstration we exploit the use of a
serial link for fast asynchronous communication in massively
parallel processing platforms connected to a DVS for realtime
implementation of bio-inspired vision processing on
spiking neural networks
A USB3.0 FPGA Event-based Filtering and Tracking Framework for Dynamic Vision Sensors
Dynamic vision sensors (DVS) are frame-free sensors
with an asynchronous variable-rate output that is ideal for hard
real-time dynamic vision applications under power and latency
constraints. Post-processing of the digital sensor output can
reduce sensor noise, extract low level features, and track objects
using simple algorithms that have previously been implemented
in software. In this paper we present an FPGA-based framework
for event-based processing that allows uncorrelated-event noise
removal and real-time tracking of multiple objects, with dynamic
capabilities to adapt itself to fast or slow and large or small
objects. This framework uses a new hardware platform based on
a Lattice FPGA which filters the sensor output and which then
transmits the results through a super-speed Cypress FX3 USB
microcontroller interface to a host computer. The packets of
events and timestamps are transmitted to the host computer at
rates of 10 Mega events per second. Experimental results are
presented that demonstrate a low latency of 10us for tracking
and computing the center of mass of a detected object.Ministerio de Economía y Competitividad TEC2012-37868-C04-0
Using FPGA for visuo-motor control with a silicon retina and a humanoid robot
The address-event representation (AER) is a
neuromorphic communication protocol for transferring
asynchronous events between VLSI chips. The event
information is transferred using a high speed digital parallel
bus. This paper present an experiment based on AER for
visual sensing, processing and finally actuating a robot. The
AER output of a silicon retina is processed by an AER filter
implemented into a FPGA to produce a mimicking behaviour
in a humanoid robot (The RoboSapiens V2). We have
implemented the visual filter into the Spartan II FPGA of the
USB-AER platform and the Central Pattern Generator (CPG)
into the Spartan 3 FPGA of the AER-Robot platform, both
developed by authors.Unión Europea IST-2001-34124 (CAVIAR)Ministerio de Ciencia y Tecnología TIC-2003-08164-C03-0
Isospin phases of vertically coupled double quantum rings under the influence of perpendicular magnetic fields
Vertically coupled double quantum rings submitted to a perpendicular magnetic
field are addressed within the local spin-density functional theory. We
describe the structure of quantum ring molecules containing up to 40 electrons
considering different inter-ring distances and intensities of the applied
magnetic field. When the rings are quantum mechanically strongly coupled, only
bonding states are occupied and the addition spectrum of the artificial
molecules resembles that of a single quantum ring, with some small differences
appearing as an effect of the magnetic field. Despite the latter has the
tendency to flatten the spectra, in the strong coupling limit some clear peaks
are still found even when that can be interpretated from the
single-particle energy levels analogously as at zero applied field, namely in
terms of closed-shell and Hund's-rule configurations. Increasing the inter-ring
distance, the occupation of the first antibonding orbitals washes out such
structures and the addition spectra become flatter and irregular. In the weak
coupling regime, numerous isospin oscillations are found as a function of .Comment: 27 pages, 11 figures. To be published in Phys. Rev.
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