Giant formation rates of ultracold molecules via Feshbach Optimized Photoassociation

Ultracold molecules offer a broad variety of applications, ranging from metrology to quantum computing. However, forming "real" ultracold molecules, {\it i.e.} in deeply bound levels, is a very difficult proposition. Here, we show how photoassociation in the vicinity of a Feshbach resonance enhance molecular formation rates by several orders of magnitude. We illustrate this effect in heteronuclear systems, and find giant rate coefficients even in deeply bound levels. We also give a simple analytical expression for the photoassociation rates, and discuss future applications of the Feshbach Optimized Photoassociation, or FOPA, technique

Toward scalable information processing with ultracold polar molecules in an electric field: a numerical investigation

We numerically investigate the possibilities of driving quantum algorithms with laser pulses in a register of ultracold NaCs polar molecules in a static electric field. We focuse on the possibilities of performing scalable logical operations by considering circuits that involve intermolecular gates (implemented on adjacent interacting molecules) to enable the transfer of information from one molecule to another during conditional laser-driven population inversions. We study the implementation of an arithmetic operation (the addition of 0 or 1 on a binary digit and a carry in) which requires population inversions only and the Deutsch-Josza algorithm which requires a control of the phases. Under typical experimental conditions, our simulations show that high fidelity logical operations involving several qubits can be performed in a time scale of a few hundred of microseconds, opening promising perspectives for the manipulation of a large number of qubits in these systems

Feshbach resonances in ultracold ^{6,7}Li + ^{23}Na atomic mixtures

We report a theoretical study of Feshbach resonances in $^{6}$Li + $^{23}$Na and $^{7}$Li + $^{23}$Na mixtures at ultracold temperatures using new accurate interaction potentials in a full quantum coupled-channel calculation. Feshbach resonances for $l=0$ in the initial collisional open channel $^6$Li$(f=1/2, m_f=1/2) + ^{23}$Na$(f=1, m_f=1)$ are found to agree with previous measurements, leading to precise values of the singlet and triplet scattering lengths for the $^{6,7}$Li$+^{23}$Na pairs. We also predict additional Feshbach resonances within experimentally attainable magnetic fields for other collision channels.Comment: 4 pages, 3 figure

Loss of Bim Increases T Cell Production and Function in Interleukin 7 Receptor–deficient Mice

Interleukin (IL)-7 receptor (R) signaling is essential for T and B lymphopoiesis by promoting proliferation, differentiation, and survival of cells. Mice lacking either IL-7 or the IL-7Rα chain have abnormally low numbers of immature as well as mature T and B lymphocytes. Transgenic expression of the apoptosis inhibitor Bcl-2 rescues T cell development and function in IL-7Rα–deficient mice, indicating that activation of a proapoptotic Bcl-2 family member causes death of immature and mature T cells. BH3-only proteins such as Bim, which are distant proapoptotic members of the Bcl-2 family, are essential initiators of programmed cell death and stress-induced apoptosis. We generated Bim/IL-7Rα double deficient mice and found that loss of Bim significantly increased thymocyte numbers, restored near normal numbers of mature T cells in the blood and spleen, and enhanced cytotoxic T cell responses to virus infection in IL-7Rα−/− mice. These results indicate that Bim cooperates with other proapoptotic proteins in the death of IL-7–deprived T cell progenitors in vivo, but is the major inducer of this pathway to apoptosis in mature T cells. This indicates that pharmacological inhibition of Bim function might be useful for boosting immune responses in immunodeficient patients

Efficient formation of ground state ultracold molecules via STIRAP from the continuum at a Feshbach resonance

We develop a complete theoretical description of photoassociative Stimulated Raman Adiabatic Passage (STIRAP) near a Feshbach resonance in a thermal atomic gas. We show that it is possible to use low intensity laser pulses to directly excite the continuum at a Feshbach resonance and transfer nearly the entire atomic population to the lowest rovibrational level in the molecular ground state. In case of a broad resonance, commonly found in several diatomic alkali molecules, our model predicts a transfer efficiency $\eta$ up to 97% for a given atom pair, and up to 70% when averaged over an atomic ensemble. The laser intensities and pulse durations needed for optimal transfer are $10^2-10^3$ W/cm$^2$ and several $\mu$s. Such efficiency compares to or surpasses currently available techniques for creating stable diatomic molecules, and the versatility of this approach simplifies its potential use for many molecular species

Performance of neutron-irradiated 4H-Silicon Carbide diodes subjected to Alpha radiation

The unique electrical and material properties of 4H-silicon-carbide (4H-SiC) make it a promising candidate material for high rate particle detectors. In contrast to the ubiquitously used silicon (Si), 4H-SiC offers a higher carrier saturation velocity and larger breakdown voltage, enabling a high intrinsic time resolution and mitigating pile-up effects. Additionally, as radiation hardness requirements grow more demanding, wide-bandgap materials such as 4H-SiC could offer better performance. In this work, the detector performance of 50 micron thick 4H-SiC p-in-n planar pad sensors was investigated at room temperature, using an 241Am alpha source at reverse biases of up to 1100 V. Samples subjected to neutron irradiation with fluences of up to 1e16/cm^2 were included in the study in order to quantify the radiation hardness properties of 4H-SiC. The obtained results are compared to previously performed UV-TCT studies. Samples exhibit a drop in charge collection efficiency (CCE) with increasing irradiation fluence, partially compensated at high reverse bias voltages far above full depletion voltage. A plateau of the collected charges is observed in accordance with the depletion of the volume the alpha particles penetrate for an unirradiated reference detector. For the neutron-irradiated samples, such a plateau only becomes apparent at higher reverse bias. For the highest investigated fluence, CCE behaves almost linearly with increasing reverse bias. Compared to UV-TCT measurements, the reverse bias required to deplete a sensitive volume covering full energy deposition is lower, due to the small penetration depth of the alpha particles. At the highest reverse bias, the measured CCE values agree well with earlier UV-TCT studies, with discrepancies between 1% and 5%.Comment: 10 pages (8 without references), 6 figures, 1 table, to be published in the Proceedings Section of Journal of Instrumentation (JINST) as a proceeding of iWoRiD202

Formation of deeply bound molecules via chainwise adiabatic passage

We suggest and analyze a novel technique for efficient and robust creation of dense ultracold molecular ensembles in their ground rovibrational state. In our approach a molecule is brought to the ground state through a series of intermediate vibrational states via a {\em multistate chainwise Stimulated Raman Adiabatic Passage} (c-STIRAP) technique. We study the influence of the intermediate states decay on the transfer process and suggest an approach that minimizes the population of these states, resulting in a maximal transfer efficiency. As an example, we analyze the formation of $^{87}$Rb$_{2}$ starting from an initial Feshbach molecular state and taking into account major decay mechanisms due to inelastic atom-molecule and molecule-molecule collisions. Numerical analysis suggests a transfer efficiency $>$ 90%, even in the presence of strong collisional relaxation as are present in a high density atomic gas

Endommagement sous choc dans les métaux : mesure et prédiction

National audienceShocks by means of plate impact (Al/Cu and Al/Ta) and laser impact on Al and Ta are reproduced with a viscoplastic extension of the Gurson model. Introduction of viscosity in the model allows to account for impacts at different velocities. Damage levels in the targets are analysed through microtomography measurements at the ESRF. On a laser shock on Al, the pore volume distribution curve is of the power-law type at large volumes

Interaction Network Analysis Using Semantic Similarity Based on Translation Embeddings

Biomedical knowledge graphs such as STITCH, SIDER, and Drugbank provide the basis for the discovery of associations between biomedical entities, e.g., interactions between drugs and targets. Link prediction is a paramount task and represents a building block for supporting knowledge discovery. Although several approaches have been proposed for effectively predicting links, the role of semantics has not been studied in depth. In this work, we tackle the problem of discovering interactions between drugs and targets, and propose SimTransE, a machine learning-based approach that solves this problem effectively. SimTransE relies on translating embeddings to model drug-target interactions and values of similarity across them. Grounded on the vectorial representation of drug-target interactions, SimTransE is able to discover novel drug-target interactions. We empirically study SimTransE using state-of-the-art benchmarks and approaches. Experimental results suggest that SimTransE is competitive with the state of the art, representing, thus, an effective alternative for knowledge discovery in the biomedical domain