37,609 research outputs found
A Fabry-Perot interferometer with quantum mirrors: nonlinear light transport and rectification
Optical transport represents a natural route towards fast communications, and
it is currently used in large scale data transfer. The progressive
miniaturization of devices for information processing calls for the microscopic
tailoring of light transport and confinement at length scales appropriate for
the upcoming technologies. With this goal in mind, we present a theoretical
analysis of a one-dimensional Fabry-Perot interferometer built with two highly
saturable nonlinear mirrors: a pair of two-level systems. Our approach captures
non-linear and non-reciprocal effects of light transport that were not reported
previously. Remarkably, we show that such an elementary device can operate as a
microscopic integrated optical rectifier
Contributions of point extragalactic sources to the Cosmic Microwave Background bispectrum
All the analyses of Cosmic Microwave Background (CMB) temperature maps
up--to--date show that CMB anisotropies follow a Gaussian distribution. On the
other hand, astrophysical foregrounds which hamper the detection of the CMB
angular power spectrum, are not Gaussian distributed on the sky. Therefore,
they should give a sizeable contribution to the CMB bispectrum. In fact, the
first year data of the Wilkinson Microwave Anisotropy Probe (WMAP) mission have
allowed the {\it first} detection of the extragalactic source contribution to
the CMB bispectrum at 41 GHz and, at the same time, much tighter limits than
before to non--Gaussian primordial fluctuations. In view of the above and for
achieving higher precision in current and future CMB measurements of
non--Gaussianity, in this paper we discuss a comprehensive assessment of the
bispectrum due to either uncorrelated and clustered extragalactic point sources
in the whole frequency interval around the CMB intensity peak. Our
calculations, based on current cosmological evolution models for sources, show
that the reduced angular bispectrum due to point sources, , should be
detectable in all WMAP and Planck frequency channels. We also find agreement
with the results on at 41 GHz coming from the analysis of the first
year WMAP data. Moreover, by comparing with the primordial reduced CMB
bispectrum, we find that only the peak value of the primordial bispectrum
(which appears at ) results greater than in a frequency
window around the intensity peak of the CMB. The amplitude of this window
basically depends on the capability of the source detection algorithms (i.e.,
on the achievable flux detection limit, , for sources).Comment: 26 pages, 6 Figures, use AasTex5.0, ApJ, in press, Oct. 10, 2003
Issu
Measurement of the electron drift velocity for directional dark matter detectors
Three-dimensional track reconstruction is a key issue for directional Dark
Matter detection. It requires a precise knowledge of the electron drift
velocity. Magboltz simulations are known to give a good evaluation of this
parameter. However, large TPC operated underground on long time scale may be
characterized by an effective electron drift velocity that may differ from the
value evaluated by simulation. In situ measurement of this key parameter is
hence a way to avoid bias in the 3D track reconstruction. We present a
dedicated method for the measurement of the electron drift velocity with the
MIMAC detector. It is tested on two gas mixtures : and . We also show that adding allows us to lower the
electron drift velocity while keeping almost the same Fluorine content of the
gas mixture.Comment: Proceedings of the 4th international conference on Directional
Detection of Dark Matter (CYGNUS 2013), 10-12 June 2013, Toyama, Japa
MIMAC: MIcro-tpc MAtrix of Chambers for dark matter directional detection
Directional detection of non-baryonic Dark Matter is a promising search
strategy for discriminating WIMP events from neutrons, the ultimate background
for dark matter direct detection. This strategy requires both a precise
measurement of the energy down to a few keV and 3D reconstruction of tracks
down to a few mm. The MIMAC (MIcro-tpc MAtrix of Chambers) collaboration has
developed in the last years an original prototype detector based on the direct
coupling of large pixelized micromegas with a special developed fast
self-triggered electronics showing the feasibility of a new generation of
directional detectors. The first bi-chamber prototype has been installed at
Modane, underground laboratory in June 2012. The first undergournd background
events, the gain stability and calibration are shown. The first spectrum of
nuclear recoils showing 3D tracks coming from the radon progeny is presented.Comment: Proceedings of the 4th International Conference on Directional Dark
Matter Detection CYGNUS2013, held in Toyoma (Japan), June 201
Entropy inequalities and Bell inequalities for two-qubit systems
Sufficient conditions for (the non-violation of) the Bell-CHSH inequalities
in a mixed state of a two-qubit system are: 1) The linear entropy of the state
is not smaller than 0.5, 2) The sum of the conditional linear entropies is
non-negative, 3) The von Neumann entropy is not smaller than 0.833, 4) The sum
of the conditional von Neumann entropies is not smaller than 0.280.Comment: Errors corrected. See L. Jakobcyk, quant-ph/040908
In situ measurement of the electron drift velocity for upcoming directional Dark Matter detectors
Three-dimensional track reconstruction is a key issue for directional Dark
Matter detection and it requires a precise knowledge of the electron drift
velocity. Magboltz simulations are known to give a good evaluation of this
parameter. However, large TPC operated underground on long time scale may be
characterized by an effective electron drift velocity that may differ from the
value evaluated by simulation. In situ measurement of this key parameter is
hence needed as it is a way to avoid bias in the 3D track reconstruction. We
present a dedicated method for the measurement of the electron drift velocity
with the MIMAC detector. It is tested on two gas mixtures: CF4 and CF4 + CHF3.
The latter has been chosen for the MIMAC detector as we expect that adding CHF3
to pure CF4 will lower the electron drift velocity. This is a key point for
directional Dark Matter as the track sampling along the drift field will be
improved while keeping almost the same Fluorine content of the gas mixture. We
show that the drift velocity at 50 mbar is reduced by a factor of about 5 when
adding 30% of CHF3.Comment: 19 pages, 14 figures. Minor corrections, matches published version in
JINS
The Resistive-Plate WELL with Argon mixtures - a robust gaseous radiation detector
A thin single-element THGEM-based, Resistive-Plate WELL (RPWELL) detector was
operated with 150 GeV/c muon and pion beams in Ne/(5%CH), Ar/(5%CH) and
Ar/(7%CO); signals were recorded with 1 cm square pads and SRS/APV25
electronics. Detection efficiency values greater than 98% were reached in all
the gas mixtures, at average pad multiplicity of 1.2. The use of the
10{\Omega}cm resistive plate resulted in a completely discharge-free
operation also in intense pion beams. The efficiency remained essentially
constant at 98-99% up to fluxes of 10Hz/cm, dropping by a few %
when approaching 10 Hz/cm. These results pave the way towards
cost-effective, robust, efficient, large-scale detectors for a variety of
applications in future particle, astro-particle and applied fields. A potential
target application is digital hadron calorimetry.Comment: presented at the 2016 VIenna Conf. On instrumentation. Submitted to
the Conference proceeding
MIMAC : A micro-tpc matrix for directional detection of dark matter
Directional detection of non-baryonic Dark Matter is a promising search
strategy for discriminating WIMP events from background. However, this strategy
requires both a precise measurement of the energy down to a few keV and 3D
reconstruction of tracks down to a few mm. To achieve this goal, the MIMAC
project has been developed. It is based on a gaseous micro-TPC matrix, filled
with CF4 and CHF3. The first results on low energy nuclear recoils (H, F)
obtained with a low mono-energetic neutron field are presented. The discovery
potential of this search strategy is discussed and illustrated by a realistic
case accessible to MIMAC.Comment: 6 pages, Proc. of the fifth international symposium on large TPCs for
low energy rare event detection, Paris, France, Dec. 2010. To appear in
Journal of Physic
Many-particle confinement by constructed disorder and quantum computing
Many-particle confinement (localization) is studied for a 1D system of
spinless fermions with nearest-neighbor hopping and interaction, or
equivalently, for an anisotropic Heisenberg spin-1/2 chain. This system is
frequently used to model quantum computers with perpetually coupled qubits. We
construct a bounded sequence of site energies that leads to strong
single-particle confinement of all states on individual sites. We show that
this sequence also leads to a confinement of all many-particle states in an
infinite system for a time that scales as a high power of the reciprocal
hopping integral. The confinement is achieved for strong interaction between
the particles while keeping the overall bandwidth of site energies
comparatively small. The results show viability of quantum computing with
time-independent qubit coupling.Comment: An invited paper for the topical issue of J. Opt. B on quantum
contro
Universal optimal broadband photon cloning and entanglement creation in one dimensional atoms
We study an initially inverted three-level atom in the lambda configuration
embedded in a waveguide, interacting with a propagating single-photon pulse.
Depending on the temporal shape of the pulse, the system behaves either as an
optimal universal cloning machine, or as a highly efficient deterministic
source of maximally entangled photon pairs. This quantum transistor operates
over a wide range of frequencies, and can be implemented with today's
solid-state technologies.Comment: 5 pages, 3 figure
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