Extended Bose-Hubbard models with Rydberg macrodimer dressing

Extended Hubbard models have proven to bear novel quantum states, but their experimental realization remains challenging. In this work we propose to use bosonic quantum gases dressed with molecular bound states in Rydberg interaction potentials for the observation of these quantum states. We study the molecular Rabi coupling with respect to principal quantum number and trapping frequency of the ground state atoms for various molecular potentials of Rubidium and Potassium, and the hereby resulting dressed interaction strength. Additionally, we propose a two-color excitation scheme which significantly increases the dressed interaction and cancels AC Stark shifts limiting the atomic motion in the itinerant regime. We study the various equilibrium phases of the corresponding extended Bose-Hubbard model by means of the Cluster Gutzwiller approach and perform time evolution simulations via the Lindblad master equation. We find a supersolid phase by slowly ramping the molecular Rabi coupling of an initially prepared superfluid and discuss the role of dissipation.Comment: 11 pages, 7 figure

The Primordial Binary Population - I: A near-infrared adaptive optics search for close visual companions to A star members of Scorpius OB2

We present the results of a near-infrared adaptive optics survey with the aim to detect close companions to Hipparcos members in the three subgroups of the nearby OB association Sco OB2: Upper Scorpius (US), Upper Centaurus Lupus (UCL) and Lower Centaurus Crux (LCC). We have targeted 199 A-type and late B-type stars in the Ks band, and a subset also in the J and H band. We find 151 stellar components other than the target stars. A brightness criterion is used to separate these components into 77 background stars and 74 candidate physical companion stars. Out of these 74 candidate companions, 41 have not been reported before (14 in US; 13 in UCL; 14 in LCC). Companion star masses range from 0.1 to 3 Msun. The mass ratio distribution follows f(q) = q^-0.33, which excludes random pairing. No close (rho < 3.75'') companion stars or background stars are found in the magnitude range 12 < Ks < 14. The lack of stars with these properties cannot be explained by low-number statistics, and may imply a lower limit on the companion mass of ~ 0.1 Msun. Close stellar components with Ks > 14 are observed. If these components are very low-mass companion stars, a gap in the companion mass distribution might be present. The small number of close low-mass companion stars could support the embryo-ejection formation scenario for brown dwarfs. Our findings are compared with and complementary to visual, spectroscopic, and astrometric data on binarity in Sco OB2. We find an overall companion star fraction of 0.52 in this association. This paper is the first step toward our goal to derive the primordial binary population in Sco OB2.Comment: 27 pages, to accepted by A&

Time-of-arrival distributions for continuous quantum systems and application to quantum backflow

Using standard results from statistics, we show that for any continuous quantum system (Gaussian or otherwise) and any observable Â (position or otherwise), the distribution ⁡() of time measurement at a fixed state can be inferred from the distribution ⁡() of a state measurement at a fixed time via the transformation ⁡()∝ | ⁄ ⁢∫−∞⁡() | . This finding suggests that the answer to the long-lasting time-of-arrival problem is in fact secretly hidden within the Born rule and therefore does not require the introduction of a time operator or a commitment to a specific (e.g., Bohmian) ontology. The generality and versatility of the result are illustrated by applications to the time of arrival at a given location for a free particle in a superposed state and to the time required to reach a given velocity for a free-falling quantum particle. Our approach also offers a potentially promising new avenue toward the design of an experimental protocol for the yet-to-be-performed observation of the phenomenon of quantum backflow

The primordial binary population II: Recovering the binary population for intermediate mass stars in Sco OB2

We characterize the binary population in the young and nearby OB association Scorpius OB2 using available observations of visual, spectroscopic, and astrometric binaries with intermediate-mass primaries. We take into account observational biases by comparing the observations with simulated observations of model associations. The available data indicate a large binary fraction (> 70% with 3sigma confidence), with a large probability that all intermediate mass stars in Sco OB2 are part of a binary system. The binary systems have a mass ratio distribution of the form f(q) ~ q^-0.4. Sco OB2 has a semi-major axis distribution of the form f(log a) ~ constant (Opik's law), in the range 5-5e6 Rsun. The log-normal period distribution of Duquennoy & Mayor results in too few spectroscopic binaries, even if the model binary fraction is 100%. Sco OB2 is a young association with a low stellar density; its current population is expected to be very similar to the primordial population. The fact that practically all stars in Sco OB2 are part of a binary (or multiple) system demonstrates that multiplicity is a fundamental factor in the star formation process, at least for intermediate mass stars.Comment: 36 pages, 11 figures, accepted by A&

Le métier de chef de projet comme activité prudentielle.

Si la gestion de projet est une activité désormais répandue dans les entreprises, le contenu du travail qu’elle implique reste paradoxalement mal connu. En s’appuyant sur une enquête menée auprès de chefs de projet d’un groupe industriel et sur les catégories de l’activité « prudentielle » proposées par Florent Champy, cet article rend intelligible ce contenu. Il montre que le chef de projet adopte un regard global sur son projet, surveille les contingences pouvant nuire à son déroulement et mobilise un « sens du possible » pour résoudre les problèmes auxquels il est confronté et arbitrer entre des exigences contradictoires. Le lien de subordination inhérent à son statut de salarié contraint son autonomie, mais lui procure aussi un certain nombre d’appuis organisationnels confortant la construction de sa vision globale du projet, de sa vigilance et de son sens du possible : la prudence apparaît sous la forme d’une qualité distribuée dans un réseau étroit de dispositifs organisationnels.The paper, based on a survey conducted with project managers of an industrial group, sheds light on the effective content of project management. Indeed, whereas this task has a real social visibility, its content is not well known. This text mobilizes the categories of “prudential activity” put forward by Florent Champy and shows that the project manager adopts a global view of his project, monitors the contingencies that may impede project progress, uses both his intuition and his experience to solve his problems and to arbitrate between conflicting requirements. The relationship of subordination that results from his status as an employee limits his autonomy, but also gives him organizational supports that consolidate his global view, his vigilance, and his intuition: prudence appears as a quality shared out within a narrow network of organizational devices

Evaluation of kernel low-rank compressed sensing in preclinical diffusion magnetic resonance imaging

Compressed sensing (CS) is widely used to accelerate clinical diffusion MRI acquisitions, but it is not widely used in preclinical settings yet. In this study, we optimized and compared several CS reconstruction methods for diffusion imaging. Different undersampling patterns and two reconstruction approaches were evaluated: conventional CS, based on Berkeley Advanced Reconstruction Toolbox (BART-CS) toolbox, and a new kernel low-rank (KLR)-CS, based on kernel principal component analysis and low-resolution-phase (LRP) maps. 3D CS acquisitions were performed at 9.4T using a 4-element cryocoil on mice (wild type and a MAP6 knockout). Comparison metrics were error and structural similarity index measure (SSIM) on fractional anisotropy (FA) and mean diffusivity (MD), as well as reconstructions of the anterior commissure and fornix. Acceleration factors (AF) up to 6 were considered. In the case of retrospective undersampling, the proposed KLR-CS outperformed BART-CS up to AF = 6 for FA and MD maps and tractography. For instance, for AF = 4, the maximum errors were, respectively, 8.0% for BART-CS and 4.9% for KLR-CS, considering both FA and MD in the corpus callosum. Regarding undersampled acquisitions, these maximum errors became, respectively, 10.5% for BART-CS and 7.0% for KLR-CS. This difference between simulations and acquisitions arose mainly from repetition noise, but also from differences in resonance frequency drift, signal-to-noise ratio, and in reconstruction noise. Despite this increased error, fully sampled and AF = 2 yielded comparable results for FA, MD and tractography, and AF = 4 showed minor faults. Altogether, KLR-CS based on LRP maps seems a robust approach to accelerate preclinical diffusion MRI and thereby limit the effect of the frequency drift

Functional Discretization of Space Using Gaussian Processes for Road Intersection

International audienceThis paper propose a new framework to discretize the space within and around a cross intersection. The main purpose of our approach is to capture the manner in which drivers manoeuvre in an intersection in order to facilitate and understand the decision-making tasks. Gaussian processes are used to learn and predict the most likely trajectories taken by multiple drivers in different situations. The merging and crossing areas are found by searching for the overlap between two predicted trajectories, whereas the area approaching the intersection is discretized by using the most probable occupancy. The generated areas are stored in a map. It was possible to show the correlation between this discretization and the drivers’ behaviour by looking at how the proposed framework also discretizes the velocity profile, which can then be applied to decision making