1,839 research outputs found
Entanglement between a telecom photon and an on-demand multimode solid-state quantum memory
Entanglement between photons at telecommunication wavelengths and long-lived
quantum memories is one of the fundamental requirements of long-distance
quantum communication. Quantum memories featuring on-demand read-out and
multimode operation are additional precious assets that will benefit the
communication rate. In this work we report the first demonstration of
entanglement between a telecom photon and a collective spin excitation in a
multimode solid-state quantum memory. Photon pairs are generated through widely
non-degenerate parametric down-conversion, featuring energy-time entanglement
between the telecom-wavelength idler and a visible signal photon. The latter is
stored in a Pr:YSiO crystal as a spin wave using the full Atomic
Frequency Comb scheme. We then recall the stored signal photon and analyze the
entanglement using the Franson scheme. We measure conditional fidelities of
for excited-state storage, enough to violate a CHSH inequality, and
for spin-wave storage. Taking advantage of the on-demand read-out
from the spin state, we extend the entanglement storage in the quantum memory
for up to 47.7~s, which could allow for the distribution of entanglement
between quantum nodes separated by distances of up to 10 km
Biophotons and emergence of quantum coherence : a diffusion entropy analysis
We study the emission of photons from germinating seeds using an experimental technique designed to detect light of extremely small intensity. We analyze the dark count signal without germinating seeds as well as the photon emission during the germination process. The technique of analysis adopted here, called diffusion entropy analysis (DEA) and originally designed to measure the temporal complexity of astrophysical, sociological and physiological processes, rests on Kolmogorov complexity. The updated version of DEA used in this paper is designed to determine if the signal complexity is generated either by non-ergodic crucial events with a non-stationary correlation function or by the infinite memory of a stationary but non-integrable correlation function or by a mixture of both processes. We find that dark count yields the ordinary scaling, thereby showing that no complexity of either kinds may occur without any seeds in the chamber. In the presence of seeds in the chamber anomalous scaling emerges, reminiscent of that found in neuro-physiological processes. However, this is a mixture of both processes and with the progress of germination the non-ergodic component tends to vanish and complexity becomes dominated by the stationary infinite memory. We illustrate some conjectures ranging from stress induced annihilation of crucial events to the emergence of quantum coherence
Simulations of Hot Bubbles in the ICM
We review the general properties of the intracluster medium (ICM) in clusters
that host a cooling flow, and in particular the effects on the ICM of the
injection of hot plasma by a powerful active galactic nucleus (AGN). It is
observed that, in some cases, the hot plasma produces cavities in the ICM that
finally detach and rise, perhaps buoyantly. The gas dynamics induced by the
rising bubbles can help explain the absence of a cooled gas component in
clusters with a cooling flow. This scenario is explored using numerical
simulations.Comment: 13 pages, no figures. Accepted for publication in Modern Physics
Letters
The On-Site Analysis of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) observatory will be one of the largest
ground-based very high-energy gamma-ray observatories. The On-Site Analysis
will be the first CTA scientific analysis of data acquired from the array of
telescopes, in both northern and southern sites. The On-Site Analysis will have
two pipelines: the Level-A pipeline (also known as Real-Time Analysis, RTA) and
the level-B one. The RTA performs data quality monitoring and must be able to
issue automated alerts on variable and transient astrophysical sources within
30 seconds from the last acquired Cherenkov event that contributes to the
alert, with a sensitivity not worse than the one achieved by the final pipeline
by more than a factor of 3. The Level-B Analysis has a better sensitivity (not
be worse than the final one by a factor of 2) and the results should be
available within 10 hours from the acquisition of the data: for this reason
this analysis could be performed at the end of an observation or next morning.
The latency (in particular for the RTA) and the sensitivity requirements are
challenging because of the large data rate, a few GByte/s. The remote
connection to the CTA candidate site with a rather limited network bandwidth
makes the issue of the exported data size extremely critical and prevents any
kind of processing in real-time of the data outside the site of the telescopes.
For these reasons the analysis will be performed on-site with infrastructures
co-located with the telescopes, with limited electrical power availability and
with a reduced possibility of human intervention. This means, for example, that
the on-site hardware infrastructure should have low-power consumption. A
substantial effort towards the optimization of high-throughput computing
service is envisioned to provide hardware and software solutions with
high-throughput, low-power consumption at a low-cost.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
On the origin of radio-loudness in AGNs and its relationship with the properties of the central supermassive black hole
We investigate the relationship between the mass of central supermassive
black holes and the radio loudness of active galactic nuclei. We use the most
recent calibrations to derive virial black hole masses for samples of radio
loud QSOs for which relatively small masses (M_BH<10^8 M_sun) have been
estimated in the literature. We take into account the effect of radiation
pressure on the BLR which reduces the effective gravitational potential
experienced by the broad-line clouds and affects the mass estimates of bright
quasars. We show that in well defined samples of nearby low luminosity AGNs,
QSOs and AGNs from the SDSS, radio-loud (RL) AGN invariably host SMBHs
exceeding ~10^8 M_sun. On the other hand, radio-quiet (RQ) AGNs are associated
with a much larger range of black hole masses. The overall result still holds
even without correcting the BH mass estimates for the effects of radiation
pressure. We present a conjecture based on these results, which aims at
explaining the origin of radio-loudness in terms of two fundamental parameters:
the spin of the black hole and the black hole mass. We speculate that in order
to produce a RL AGN both of the following requirements must be satisfied: 1)the
black hole mass M_BH has to be larger than ~10^8 M_sun; 2)the spin of the BH
must be significant, in order to satisfy theoretical requirements. Taking into
account the most recent observations, we envisage a scenario in which the
merger history of the host galaxy plays a fundamental role in accounting for
both the properties of the AGN and the galaxy morphology, which in our picture
are strictly linked. RL sources might be obtained only through major dry
mergers involving BH of large mass, which would give rise to both the core
morphology and the significant black hole spin needed.Comment: 11 pages, 4 figures, accepted for publication in MNRA
The Mediterranean ocean Forecasting System
The Mediterranean Forecasting System (MFS) is operationally working since year 2000 and it is continuously improved in the frame of international projects. The system is part of the Mediterranean Operational Oceanography Network-MOON and MFS is coordinated and operated by the Italian Group of Operational Oceanography (GNOO). The latest upgrades and integration to MFS has been undertaken in the EU-MERSEA and BOSS4GMES Projects. Since October 2005 ten days forecasts are produced daily as well as 15 days of analyses once a week. The daily forecast and weekly analysis data are available in real time to the users through a dedicated ftp service and every day a web bulletin is published on the web site (http://gnoo.bo.ingv.it/mfs). A continuous evaluation in near real time of the forecasts and analyses produced by MFS has been developed in order to continuously verify the system and to provide useful information to the users. The R&D is focused on different aspects of the system. A new basin scale ocean model nested with operational MERCATOR global model has been developed and run in real time operationally for a test period together with a new assimilation scheme based on the 3DVAR. This system is now under evaluation. Important activities have been carried out to: implement and test a Bayesian methodologies of Ensemble and Super-Ensemble for the Mediterranean sea; produce 20 years of re-analysis; re-formulate the air-sea fluxes bulk formulae; develop dedicated products to support particular request of end users such as: indicators, real time oil spill forecasting, search & rescue.EUROGOOS and European CommissionPublishedExeter, UK4.6. Oceanografia operativa per la valutazione dei rischi in aree marineope
WARP liquid argon detector for dark matter survey
The WARP programme is a graded programme intended to search for cold Dark
Matter in the form of WIMP's. These particles may produce via weak interactions
nuclear recoils in the energy range 10-100 keV. A cryogenic noble liquid like
argon, already used in the realization of very large detector, permits the
simultaneous detection of both ionisation and scintillation induced by an
interaction, suggesting the possibility of discriminating between nuclear
recoils and electrons mediated events. A 2.3 litres two-phase argon detector
prototype has been used to perform several tests on the proposed technique.
Next step is the construction of a 100 litres sensitive volume device with
potential sensitivity a factor 100 better than presently existing experiments.Comment: Proceeding of the 6th UCLA Symposium on Sources and detection of Dark
Matter and dark Energy in the Univers
Genetic determinants of complement activation in the general population
Complement is a fundamental innate immune response component. Its alterations are associated with severe systemic diseases. To illuminate the complement's genetic underpinnings, we conduct genome-wide association studies of the functional activity of the classical (CP), lectin (LP), and alternative (AP) complement pathways in the Cooperative Health Research in South Tyrol study (n = 4,990). We identify seven loci, encompassing 13 independent, pathway-specific variants located in or near complement genes (CFHR4, C7, C2, MBL2) and non-complement genes (PDE3A, TNXB, ABO), explaining up to 74% of complement pathways' genetic heritability and implicating long-range haplotypes associated with LP at MBL2. Two-sample Mendelian randomization analyses, supported by transcriptome- and proteome-wide colocalization, confirm known causal pathways, establish within-complement feedback loops, and implicate causality of ABO on LP and of CFHR2 and C7 on AP. LP causally influences collectin-11 and KAAG1 levels and the risk of mouth ulcers. These results build a comprehensive resource to investigate the role of complement in human health
Cluster di Calcolo di OAS-Bologna e Software Scientifico disponibile
All’interno dell’ Osservatorio di Astrofisica e Scienza dello Spazio di Bologna (OAS), da sempre abbiamo avuto la necessità di strumenti di calcolo potenti e condivisi su cui gli scienziati possano svolgere le elaborazioni sui dati scientifici di Progetti e Missioni.
Il Cluster OAS nasce proprio per soddisfare questa esigenza ed è ospitato nel Centro di Calcolo del plesso OAS presso il CNR di Bologna. Tutti gli afferenti a OAS possono chiedere di essere registrati nel sistema di autenticazione LDAP del Cluster e in questo modo accedere via Internet ai nodi di login da dove possono sottomettere le loro elaborazioni.
Ci sono due modalità di usare il cluster: quella interattiva e quella batch più classica per un Cluster. L’accesso interattivo consente di lanciare in tempo reale le elaborazioni anche in maniera grafica tramite opportuni programmi si console virtuale, questo tipo di elaborazione viene svolta direttamente nei nodi di login. La modalità batch sfrutta il meccanismo a code, slurm, per sottomettere i lavori in maniera organizzata ai più potenti nodi di calcolo che non sono direttamente utilizzabili dagli utenti.
Il cluster inoltre fornisce spazio di archiviazione condiviso organizzato in HOME per i dati personali degli utenti, DATA per i risultati delle elaborazioni PROGRAMMI per la memorizzazione dei moduli di elaborazione e LUSTRE per il calcolo parallelo.
I vantaggi di avere un Cluster sono che gli utenti trovano i programmi e compilatori di cui necessitano già installati nelle principali versioni e hanno a disposizione una buona potenza di calcolo e spazio di storage per poter lavorare molto più agevolmente rispetto ai propri computer personali.
Il Cluster OAS non ha una potenza paragonabile ai grandi Cluster Commerciali e di Ricerca, ma essendo ritagliato sulle esigenze degli afferenti a OAS risponde bene alle esigenze dell'istituto e può servire come Nave Scuola per poter poi accedere a strutture più grandi qualora fosse necessario.
Nel documento saranno illustrate nel dettaglio le caratteristiche Hardware e Software del Cluster, compresi tutti i principali Software scientifici installati di cui si spiega brevemente l’utilizzo
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