848 research outputs found
Using Spontaneous Emission of a Qubit as a Resource for Feedback Control
Persistent control of a transmon qubit is performed by a feedback protocol
based on continuous heterodyne measurement of its fluorescence. By driving the
qubit and cavity with microwave signals whose amplitudes depend linearly on the
instantaneous values of the quadratures of the measured fluorescence field, we
show that it is possible to stabilize permanently the qubit in any targeted
state. Using a Josephson mixer as a phase-preserving amplifier, it was possible
to reach a total measurement efficiency =35%, leading to a maximum of 59%
of excitation and 44% of coherence for the stabilized states. The experiment
demonstrates multiple-input multiple-output analog Markovian feedback in the
quantum regime.Comment: Supplementary material can be found as an ancillary objec
PARISROC, a Photomultiplier Array Integrated Read Out Chip
PARISROC is a complete read out chip, in AMS SiGe 0.35 !m technology, for
photomultipliers array. It allows triggerless acquisition for next generation
neutrino experiments and it belongs to an R&D program funded by the French
national agency for research (ANR) called PMm2: ?Innovative electronics for
photodetectors array used in High Energy Physics and Astroparticles?
(ref.ANR-06-BLAN-0186). The ASIC (Application Specific Integrated Circuit)
integrates 16 independent and auto triggered channels with variable gain and
provides charge and time measurement by a Wilkinson ADC (Analog to Digital
Converter) and a 24-bit Counter. The charge measurement should be performed
from 1 up to 300 photo- electrons (p.e.) with a good linearity. The time
measurement allowed to a coarse time with a 24-bit counter at 10 MHz and a fine
time on a 100ns ramp to achieve a resolution of 1 ns. The ASIC sends out only
the relevant data through network cables to the central data storage. This
paper describes the front-end electronics ASIC called PARISROC.Comment: IEEE Nuclear Science Symposium an Medical Imaging Conference (2009
NSS/MIC
Widely tunable, non-degenerate three-wave mixing microwave device operating near the quantum limit
We present the first experimental realization of a widely frequency tunable,
non-degenerate three-wave mixing device for quantum signals at GHz frequency.
It is based on a new superconducting building-block consisting of a ring of
four Josephson junctions shunted by a cross of four linear inductances. The
phase configuration of the ring remains unique over a wide range of magnetic
fluxes threading the loop. It is thus possible to vary the inductance of the
ring with flux while retaining a strong, dissipation-free, and noiseless
non-linearity. The device has been operated in amplifier mode and its noise
performance has been evaluated by using the noise spectrum emitted by a voltage
biased tunnel junction at finite frequency as a test signal. The unprecedented
accuracy with which the crossover between zero-point-fluctuations and shot
noise has been measured provides an upper-bound for the noise and dissipation
intrinsic to the device.Comment: Accepted for Physical Review Letters. Supplementary material can be
found in the source packag
Sea ice and biological production variability reconstructed in the Adélie Basin, East Antarctica, during the late Holocene
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GPCR-OKB: the G protein coupled receptor oligomer knowledge base
Rapid expansion of available data about G Protein Coupled Receptor (GPCR) dimers/oligomers over the past few years requires an effective system to organize this information electronically. Based on an ontology derived from a community dialog involving colleagues using experimental and computational methodologies, we developed the GPCR-Oligomerization Knowledge Base (GPCR-OKB). GPCR-OKB is a system that supports browsing and searching for GPCR oligomer data. Such data were manually derived from the literature. While focused on GPCR oligomers, GPCR-OKB is seamlessly connected to GPCRDB, facilitating the correlation of information about GPCR protomers and oligomers
Absolute Fluorescence Spectrum and Yield Measurements for a wide range of experimental conditions
For the JEM-EUSO CollaborationThe fluorescence yield is a key ingredient in cosmic ray energy determination. It is sensitive to pressure, temperature and humidity. Up to now the fluorescence yield of the brightest line at 337 nm has been measured in an absolute way in one set of conditions, whereas fluorescence yields at the other wavelengths have been relatively measured for different conditions. Thus, absolute calibration for all the lines is unclear. We will do all measurements at once using the same apparatus: all the lines will be measured absolutely and not relatively for all conditions. For that we will use the 3-5 MeV electron beam of the PHIL accelerator (Photon Injector at LAL), shooting in a box filled with air at varying pressures, temperatures and humidity. Delta rays resulting from the beam collisions with Nitrogen are responsible for the light yield. The light detection probability should be independent of its emission point especially at the delta ray stopping point. The idea is to use an integrating sphere, encapsulated in a vessel where pressure, temperature and humidity can be varied. This sphere will have two ports for the beam (in and out), one more port dedicated to a NIST photodiode for calibration and another port feeding optical fibers going to: A) a grating spectrometer equipped with cooled CCD. B) a photomultiplier with BG3 filters to measure directly the integrated yield. Calibrations at the percent level, will give each line spectrum yields with a precision between 2 to 5%. A special issue will be to estimate the leakage due to "high energy" delta rays. Thus, we the air density will be increased, the beam energy will be lowered until the beam stops inside the sphere. Then, the energy loss will be precisely derived from the Bethe-Bloch formula. We will present the set-up
The past : a compass for future earth
Antarctic sea ice impacts on the ocean-atmosphere heat and gas fluxes, the formation of deep and intermediate waters, the nutrient distribution and primary productivity, the so-called ‘biological carbon pump’, one of the most active in the global ocean. In this study, we explore the link between sea ice dynamic, biological production and nutrient cycling during the late Holocene (the last 2,000 yrs) in the AdĂ©lie Basin, East Antarctica, from the well-dated sediments of the Ocean Drilling Program (ODP) Site U1357. This archive, composed from ~32 meters of seasonal to annual laminated diatomaceous sequences, allows reconstructions at an unprecedented time resolution (5-10 yrs). Our study combines records of diatom census counts and diatom-specific biomarkers (a ratio (D/T) of di- and tri-unsaturated Highly Branched Isoprenoid lipids (HBI)) as indicators of sea ice and biological production changes, XRF data as markers for terrigenous inputs and bulk nitrogen isotopes (d15N) and d15N on chlorins as proxies for reconstructing nitrogen cycle. The diatom and HBI records reveal five distinct periods. From 0 to 350 yrs AD, decreasing occurrences of sea ice-related diatom species (e.g. Fragilariopsis curta + F. cylindrus) together with low D/T values and increasing open ocean diatom species (large centrics, Chaetoceros Resting Spores (CRS)) document a progressive decline of sea ice presence during the year (>9 months per year) with spring melting occurring earlier in the year and autumn sea ice formation appearing later. In contrast, between 350 and 750 yrs AD, high production of open ocean diatom species and low low D/T values and sea ice related species indicate a short duration of sea ice cover (~10 months per year) is illustrated by a pronounced increase of sea ice-associated diatom species and high D/T values. Between ~1400 and 1850 yrs AD, seasonal sea ice strongly declines (<~7 months per year) as a result of early spring melting (increasing CRS production) and late autumn waxing (high occurrences of Thalassiosira antarctica). Longer growing seasons promoted a substantial development of phytoplankton communities (especially large centric diatoms) that conducted to lower D/T values. Consistent with diatom and HBI reconstructions, XRF data show higher Fe/Al and Zr/Al ratios values during inferred warmer periods and lower ratio values during inferred cooler and icier periods, thus supporting a strong impact of the sea ice seasonal cycle on glacial runoffs. The link between sea ice conditions, biological production and nutrient cycling is still being explored and we will discuss its relationship by combining all the cited records cited above with the d15N records that we are currently generated. Based on our results, we find that sea ice dynamic and associated diatom production in the AdĂ©lie Basin revealed an opposite climatic trend than that identified in the Northern Hemisphere for the last 2000 years. The 'Little Ice Age' (1400-1850 yrs AD) or the 'Dark Ages' (400-750 yrs AD) corresponded to warmer climate conditions in the AdĂ©lie Basin, while the 'Roman Warm Period' (0-350 yrs AD) or the 'Medieval Warm Period' (900-1200 yrs AD) were associated to colder conditions. We therefore emphasize that Northern and Southern Hemisphere climate evolved in anti-phase seesaw pattern during the late Holocene
Radio emission of extensive air shower at CODALEMA: Polarization of the radio emission along the v*B vector
Cosmic rays extensive air showers (EAS) are associated with transient radio
emission, which could provide an efficient new detection method of high energy
cosmic rays, combining a calorimetric measurement with a high duty cycle. The
CODALEMA experiment, installed at the Radio Observatory in Nancay, France, is
investigating this phenomenon in the 10^17 eV region. One challenging point is
the understanding of the radio emission mechanism. A first observation
indicating a linear relation between the electric field produced and the cross
product of the shower axis with the geomagnetic field direction has been
presented (B. Revenu, this conference). We will present here other strong
evidences for this linear relationship, and some hints on its physical origin.Comment: Contribution to the 31st International Cosmic Ray Conference, Lodz,
Poland, July 2009. 4 pages, 8 figures. v2: Typo fixed, arxiv references adde
Electron neutrino tagging through tertiary lepton detection
We discuss an experimental technique aimed at tagging electron neutrinos in
multi-GeV artificial sources on an event-by-event basis. It exploits in a novel
manner calorimetric and tracking technologies developed in the framework of the
LHC experiments and of rare kaon decay searches. The setup is suited for
slow-extraction, moderate power beams and it is based on an instrumented decay
tunnel equipped with tagging units that intercept secondary and tertiary
leptons from the bulk of undecayed \pi^+ and protons. We show that the taggers
are able to reduce the \nue contamination originating from K_e3 decays by about
one order of magnitude. Only a limited suppression (~60%) is achieved for \nue
produced by the decay-in-flight of muons; for low beam powers, similar
performance as for K_e3 can be reached supplementing the tagging system with an
instrumented beam dump.Comment: 19 pages, 7 figures; minor changes, version to appear in EPJ
A Beta Beam complex based on the machine upgrades for the LHC
The Beta Beam CERN design is based on the present LHC injection complex and
its physics reach is mainly limited by the maximum rigidity of the SPS. In
fact, some of the scenarios for the machine upgrades of the LHC, particularly
the construction of a fast cycling 1 TeV injector (``Super-SPS''), are very
synergic with the construction of a higher Beta Beam. At the energies
that can be reached by this machine, we demonstrate that dense calorimeters can
already be used for the detection of at the far location. Even at
moderate masses (40 kton) as the ones imposed by the use of existing
underground halls at Gran Sasso, the CP reach is very large for any value of
that would provide evidence of appearance at T2K or
NOA (). Exploitation of matter effects at the
CERN to Gran Sasso distance provides sensitivity to the neutrino mass hierarchy
in significant areas of the plane
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