Tight bound on coherent states quantum key distribution with heterodyne detection

We propose a new upper bound for the eavesdropper's information in the direct and reverse reconciliated coherent states quantum key distribution protocols with heterodyne detection. This bound is derived by maximizing the leaked information over the symplectic group of transformations that spans every physical Gaussian attack on individual pulses. We exhibit four different attacks that reach this bound, which shows that this bound is tight. Finally, we compare the secret key rate obtained with this new bound to the homodyne rate.Comment: 8 pages, 3 figure

Compressed intramolecular dispersion interactions.

The feasibility of the compression of localized virtual orbitals is explored in the context of intramolecular long-range dispersion interactions. Singular value decomposition (SVD) of coupled cluster doubles amplitudes associated with the dispersion interactions is analyzed for a number of long-chain systems, including saturated and unsaturated hydrocarbons and a silane chain. Further decomposition of the most important amplitudes obtained from these SVDs allows for the analysis of the dispersion-specific virtual orbitals that are naturally localized. Consistent with previous work on intermolecular dispersion interactions in dimers, it is found that three important geminals arise and account for the majority of dispersion interactions at the long range, even in the many body intramolecular case. Furthermore, it is shown that as few as three localized virtual orbitals per occupied orbital can be enough to capture all pairwise long-range dispersion interactions within a molecule

Magnetic reconnection at the termination shock in a striped pulsar wind

Most of the rotational luminosity of a pulsar is carried away by a relativistic magnetised wind in which the matter energy flux is negligible compared to the Poynting flux. Near the equatorial plane of an obliquely rotating pulsar magnetosphere, the magnetic field reverses polarity with the pulsar period, forming a wind with oppositely directed field lines. This structure is called a striped wind; dissipation of alternating fields in the striped wind is the object of our study. The aim of this paper is to study the conditions required for magnetic energy release at the termination shock of the striped pulsar wind. Magnetic reconnection is considered via analytical methods and 1D relativistic PIC simulations. An analytical condition on the upstream parameters for partial and full magnetic reconnection is derived from the conservation laws of energy, momentum and particle number density across the relativistic shock. Furthermore, by using a 1D relativistic PIC code, we study in detail the reconnection process at the termination shock. We found a very simple criterion for dissipation of alternating fields at the termination shock, depending on the upstream parameters of the flow. 1D relativistic PIC simulations are in agreement with our criterion. Thus, alternating magnetic fields annihilate easily at relativistic highly magnetised shocks.Comment: Accepted by A&

First CMB Constraints on the Inflationary Reheating Temperature

We present the first Bayesian constraints on the single field inflationary reheating era obtained from Cosmic Microwave Background (CMB) data. After demonstrating that this epoch can be fully characterized by the so-called reheating parameter, we show that it is constrained by the seven years Wilkinson Microwave Anisotropies Probe (WMAP7) data for all large and small field models. An interesting feature of our approach is that it yields lower bounds on the reheating temperature which can be combined with the upper bounds associated with gravitinos production. For large field models, we find the energy scale of reheating to be higher than those probed at the Large Hadron Collider, Ereh > 17.3 TeV at 95% of confidence. For small field models, we obtain the two-sigma lower limits Ereh > 890 TeV for a mean equation of state during reheating = -0.3 and Ereh > 390 GeV for = -0.2. The physical origin of these constraints is pedagogically explained by means of the slow-roll approximation. Finally, when marginalizing over all possible reheating history, the WMAP7 data push massive inflation under pressure (p < 2.2 at 95% of confidence where p is the power index of the large field potentials) while they slightly favor super-Planckian field expectation values in the small field models.Comment: 18 pages, 15 figures, uses RevTeX. References added, matches published versio

Non-destructive measurement of the transition probability in a Sr optical lattice clock

We present the experimental demonstration of non-destructive probing of the 1S0-3P0 clock transition probability in an optical lattice clock with 87Sr atoms. It is based on the phase shift induced by the atoms on a weak off-resonant laser beam. The method we propose is a differential measurement of this phase shift on two modulation sidebands with opposite detuning with respect to the 1S0-1P1 transition, allowing a detection limited by the photon shot noise. We have measured an atomic population of 10^4 atoms with a signal to noise ratio of 100 per cycle, while keeping more than 95% of the atoms in the optical lattice with a depth of 0.1 mK. The method proves simple and robust enough to be operated as part of the whole clock setup. This detection scheme enables us to reuse atoms for subsequent clock state interrogations, dramatically reducing the loading time and thereby improving the clock frequency stability.Comment: 4 pages, 5 figure

Spectroscopy of Na⁺·Rg and transport coefficients of Na⁺ in Rg (Rg=He-Rn)

High-level ab initio calculations are used to obtain accurate potential energy curves for Na+·Kr, Na+·Xe, and Na+·Rn. These data are used to calculate spectroscopic parameters for these three species, and the data for the whole Na+·Rg series (Rg=He-Rn) are compared. Potentials for the whole series are then used to calculate both mobilities and diffusion coefficients for Na+ moving through a bath of each of the six rare gases, under conditions that match previous experimental determinations. Different available potentials and experimental data are then statistically compared. It is concluded that the present potentials are very accurate. The potential and other data for Na+·Rn appear to be the first such reported

Concordance dans le dépistage des enfants à risque pour les difficultés d’adaptation en milieu préscolaire

Cette étude examine l'apport de l'observation participante au dépistage précoce des enfants à risque en milieu préscolaire. Cent onze enfants de trois à quatre ans sont évalués par les éducateurs de leur groupe de garderie, à partir de 17 descripteurs de l'adaptation psychosociale en garderie. Les mesures font ressortir cinq profils comportementaux différenciés. Deux correspondent à des enfants perçus comme turbulents et retirés, rejoignant les distinctions traditionnelles entre troubles extériorisés et intériorisés. L'analyse de la fiabilité interobservateur indique que les éducateurs sont plus en accord pour les enfants évalués positivement que pour ceux qu'ils perçoivent moins adaptés. Ces résultats soulignent l'intérêt de l'observation participante pour détecter les trajectoires à risque. Ils montrent cependant la nécessité d'utiliser d'autres sources d'informations convergentes dans le dépistage précoce.This study examines the advantage which participant observation provides for the early diagnosis of at-risk pre-school children. Pre-school educators used a series of 17 descriptors of psycho-social adjustment to evaluate 111 children aged 3 to 4 years. These measures were used to describe five differentiated behavioral profiles. Two profiles describe children who are perceived as turbulent and retiring, these being traditional distinctions between exteriorizing, and interiorizing problems. Analysis of inter-observer reliability indicated that educators have higher agreement among each other in regard to those children who were positively evaluated than for those perceived as less adjusted. The results confirm the relevance of participant observation for detecting at-risk behavior. The authors point out, however, the need to use other information sources in early diagnosis.Este estudio examina el aporte de la obsevacion participante en la identificaciôn precoz de ninos "a riesgo" en medio prescolar. Ciento once ninos de très a cuatro anos han sido evaluados por los educadores de sus propios grupos de guarderia utilizando 17 descriptores de adaptacion psicosocial al medio prescolar. El trabajo pone en relieve cinco perfiles comportamentales diferenciados. Dos corresponden a ninos percibidos como revoltosos y alejados, coincidiendo con las distinciones tradicionales entre problemas exteriorizados e interiorizados. El anâlisis de fiabilidad interobservador indica que los docentes concuerdan mas en los casos de parvulos evaluados positivamente que en aquellos casos percibidos como menos adaptados. Estos resultados subrayan el interés suscitado por la observacion participante para detectar trayectorias "a riesgo". Sin embargo, los resultados muestran la necesidad de utilizar otras fuentes de informacion convergentes para la identificacion precoz de ninos "a riesgo".Diese Studie untersucht den Beitrag der teilnehmenden Beobachtung zum frûhzeitigen Erkennen von Problemfâllen im Vorschulbereich. Insgesamt wurden 111 Kinder zwischen 3 und 4 Jahren von den Erziehern ihrer jeweiligen Kindergarten untersucht, und zwar an Hand von 17 Kriterien psychosozialer Anpassung im Kindergarten. Daraus ergeben sich flinf verschiedene Verhaltensprofile. Zwei davon beziehen sich auf Kinder, die als "turbulent" oder "zurûckgezogen" eingestuft wurden, was dem traditionellen Unterschied von nach innen oder auEen abgeleiteten Stôrungen entspricht. Die Analyse der Beob-achtungszuverlâssigkeit weist darauf hin, dass die Erzieher starker mit den positiv beurteilten Kindern iibereinstimmen als mit den anpassungsschwierigen. Dièse Ergebnisse unterstreichen die Be-deutung der teilnehmenden Beobachtung zum Erkennen von potentiellen Problementwicklungen. Es ergibt sich jedoch auch die Notwendigkeit zusâtzlicher Informationsquellen, die sich fur die Friiherkennung als konvergent erweisen kônnten

Hunting Down the Best Model of Inflation with Bayesian Evidence

We present the first calculation of the Bayesian evidence for different prototypical single field inflationary scenarios, including representative classes of small field and large field models. This approach allows us to compare inflationary models in a well-defined statistical way and to determine the current "best model of inflation". The calculation is performed numerically by interfacing the inflationary code FieldInf with MultiNest. We find that small field models are currently preferred, while large field models having a self-interacting potential of power p>4 are strongly disfavoured. The class of small field models as a whole has posterior odds of approximately 3:1 when compared with the large field class. The methodology and results presented in this article are an additional step toward the construction of a full numerical pipeline to constrain the physics of the early Universe with astrophysical observations. More accurate data (such as the Planck data) and the techniques introduced here should allow us to identify conclusively the best inflationary model.Comment: 12 pages, 2 figures, uses RevTeX. Misprint corrected, references added. Matches published versio

Chromatin-dependent regulation of secondary metabolite biosynthesis in fungi : is the picture complete?

Fungal secondary metabolites are small molecules that exhibit diverse biological activities exploited in medicine, industry and agriculture. Their biosynthesis is governed by co-expressed genes that often co-localize in gene clusters. Most of these secondary metabolite gene clusters are inactive under laboratory conditions, which is due to a tight transcriptional regulation. Modifications of chromatin, the complex of DNA and histone proteins influencing DNA accessibility, play an important role in this regulation. However, tinkering with well-characterised chemical and genetic modifications that affect chromatin alters the expression of only few biosynthetic gene clusters, and thus the regulation of the vast majority of biosynthetic pathways remains enigmatic. In the past, attempts to activate silent gene clusters in fungi mainly focused on histone acetylation and methylation, while in other eukaryotes many other post-translational modifications are involved in transcription regulation. Thus, how chromatin regulates the expression of gene clusters remains a largely unexplored research field. In this review, we argue that focusing on only few well-characterised chromatin modifications is significantly hampering our understanding of the chromatin-based regulation of biosynthetic gene clusters. Research on underexplored chromatin modifications and on the interplay between different modifications is timely to fully explore the largely untapped reservoir of fungal secondary metabolites.</p