Showing papers by "Robin Côté published in 2010"
TL;DR: In this paper, the minimum energy reaction path for the reaction KRb + KRb to K{sub 2 + Rb{sub s} was shown to be barrierless.
Abstract: The formation and interaction of ultracold polar molecules is a topic of active research. Understanding possible reaction paths and molecular combinations requires accurate studies of the fragment and product energetics. We have calculated accurate gradient optimized ground-state structures and zero-point corrected atomization energies for the trimers and tetramers formed by the reaction of KRb with KRb and corresponding isolated atoms. The K{sub 2}Rb and KRb{sub 2} trimers are found to have global minima at the C{sub 2v} configuration with atomization energies of 6065 and 5931 cm{sup -1} while the tetramer is found to have two stable planar structures, of D{sub 2h} and C{sub s} symmetry, which have atomization energies of 11131 cm{sup -1} and 11133 cm{sup -1}, respectively. We have calculated the minimum energy reaction path for the reaction KRb + KRb to K{sub 2} + Rb{sub 2} and found it to be barrierless.
41 citations
36 citations
TL;DR: In this article, the effects of nonuniform magnetic and optical trapping fields on low-temperature collisions of trapped molecules with slow atomic beams were investigated. But the authors focused on the effect of small-angle scattering in trap loss.
Abstract: We present a theoretical study of molecular-trap loss induced by collisions with slow atomic beams based on an explicit analysis of collision kinematics in the laboratory frame and a rigorous quantum description of atom-molecule scattering in external fields. The theory is applied to elucidate the effects of nonuniform magnetic and optical trapping fields on low-temperature collisions of OH ($J=3/2,{M}_{J}=3/2,f$) molecules with $^{4}\mathrm{He}$ atoms. Our calculations quantify the extent to which both elastic and inelastic cross sections are suppressed by external trapping fields, clarify the role of small-angle scattering in trap loss, and may benefit future experiments on collisional cooling of molecules in electromagnetic traps. The calculated cross sections for trap loss in $^{4}\mathrm{He}$ $+$ OH collisions are consistent with recent experimental observations at low beam energies [B. C. Sawyer et al., Phys. Rev. Lett. 101, 203203 (2008)], demonstrating the importance of including the effects of nonuniform trapping fields in theoretical simulations of cold collision experiments with trapped molecules and slow atomic beams.
17 citations
Journal Article•
TL;DR: In this paper, the authors have calculated accurate gradient optimized ground-state structures and zero-point corrected atomization energies for the trimers and tetramers formed by the reaction of KRb with KRb and corresponding isolated atoms.
Abstract: The formation and interaction of ultracold polar molecules is a topic of active research. Understanding possible reaction paths and molecular combinations requires accurate studies of the fragment and product energetics. We have calculated accurate gradient optimized ground-state structures and zero-point corrected atomization energies for the trimers and tetramers formed by the reaction of KRb with KRb and corresponding isolated atoms. The K2Rb and KRb2 trimers are found to have global minima at the C2v configuration with atomization energies of 6065 and 5931 cm−1 while the tetramer is found to have two stable planar structures, of D2h and Cs symmetry, which have atomization energies of 11131 cm−1 and 11133 cm−1, respectively. We have calculated the minimum energy reaction path for the reaction KRb + KRb to K2 + Rb2 and found it to be barrierless.
17 citations
TL;DR: In this article, a two-qubit phase gate is proposed to transfer a pair of atoms into the ground rovibrational state of a polar molecule with a large dipole moment, thus allowing molecules in adjacent sites to interact via their dipole-dipole interaction.
Abstract: In order to optimize quantum information processing in individual traps such as optical lattices, we propose a combined atom-molecule system. In particular, gates, initialization, and readout are suggested, using two atoms of different species--one atom carrying the qubit and the other enabling interaction. We describe in some detail the implementation of a two-qubit phase gate in which a pair of atoms is transferred into the ground rovibrational state of a polar molecule with a large dipole moment, thus allowing molecules in adjacent sites to interact via their dipole-dipole interaction. We also discuss how the reverse process could be used as a nondestructive readout tool.
14 citations
TL;DR: In this article, the authors report ab initio calculations of the X 2 Σ u + and B 2 ǫ g + states of the Be 2 + dimer.
13 citations
Journal Article•
TL;DR: In this article, a two-qubit phase gate is proposed to transfer a pair of atoms into the ground rovibrational state of a polar molecule with a large dipole moment, thus allowing molecules in adjacent sites to interact via their dipole-dipole interaction.
Abstract: In order to optimize quantum information processing in individual traps such as optical lattices, we propose a combined atom-molecule system. In particular, gates, initialization, and readout are suggested, using two atoms of different species--one atom carrying the qubit and the other enabling interaction. We describe in some detail the implementation of a two-qubit phase gate in which a pair of atoms is transferred into the ground rovibrational state of a polar molecule with a large dipole moment, thus allowing molecules in adjacent sites to interact via their dipole-dipole interaction. We also discuss how the reverse process could be used as a nondestructive readout tool.
12 citations
TL;DR: In this article, the authors investigated the excitation dynamics of Rydberg atoms in ultracold atomic samples by expanding excitation probability and the correlation function between excited atoms in powers of the isolated atom Rabi frequency.
Abstract: We investigate the excitation dynamics of Rydberg atoms in ultracold atomic samples by expanding the excitation probability and the correlation function between excited atoms in powers of the isolated atom Rabi frequency $\ensuremath{\Omega}$ In the Heisenberg picture, we give recurrence relations to calculate any order of these expansions, which are expected to be well behaved for arbitrarily strong interactions For large homogeneous samples, the explicit terms of the expansions, up to ${\ensuremath{\Omega}}^{4}$, are given and then averaged over all possible random spatial distributions of atoms for the most important cases of excitation pulses and interactions
8 citations
TL;DR: In this article, the Born-Oppenheimer potential energy curves of the chromium-rubidium heteronuclear molecule ((CrRb)-Cr-52-Rb-87), and the long-range dispersion coefficient for the interaction between ground state Cr and Rb atoms were calculated.
Abstract: We report calculations of Born-Oppenheimer potential energy curves of the chromium-rubidium heteronuclear molecule ((CrRb)-Cr-52-Rb-87), and the long-range dispersion coefficient for the interaction between ground state Cr and Rb atoms. Our calculated van der Waals coefficient (C-6 = 1770 a.u.) has an expected error of 3%. The ground state (6)Sigma(+) molecule at its equilibrium separation has a permanent electric dipole moment of d(e)(R-e = 3.34 angstrom) = 2.90 D. We investigate the hyperfine and dipolar collisions between trapped Cr and Rb atoms, finding elastic to inelastic cross section ratio of 10(2)-10(3).
6 citations
TL;DR: In this article, the formation rate of a polar molecule, LiH, via population of the intermediate excited electronic state, b {sup 3{Pi}}, followed by radiative decay was investigated.
Abstract: We compute the formation rate of a polar molecule, LiH, into the lowest triplet electronic state, a {sup 3{Sigma}+}, via population of the intermediate excited electronic state, b {sup 3{Pi}}, followed by radiative decay. We find large formation rates into the single rovibrational bound state (v=0,J=0) of the a {sup 3{Sigma}+}, which can be explained by the unusually large overlap of its wave function with those of the two upper-most bound levels of the b {sup 3{Pi}}. With conservative parameters, we estimate that over 10{sup 4} molecules/s could be produced in the single rovibrational level of the a {sup 3{Sigma}+} state. We also discuss scattering properties of LiH triplet molecules and their relevance to ultracold chemical reactions.
5 citations
TL;DR: In this article, a theoretical investigation of the X-ray emissions induced by charge exchange collisions of fully stripped solar wind ions with the heliospheric hydrogen atoms was performed, and the authors predicted the polarization of charge exchange X-rays to be between 3% and 8%, depending on the line-of-sight geometry, solar wind ion velocity, and selected emission lines.
Abstract: We report results of a theoretical investigation of polarization of the X-ray emissions induced in charge-exchange collisions of fully stripped solar wind ions C$^{6+}$ and O$^{8+}$ with the heliospheric hydrogen atoms. The polarization of X-ray emissions has been computed for line-of-sight observations within the ecliptic plane as a function of solar wind ion velocities, including a range of velocities corresponding to the slow and fast solar wind, and Coronal Mass Ejections. To determine the variability of polarization of heliospheric X-ray emissions, the polarization has been computed for solar minimum conditions with self-consistent parameters of the solar wind plasma and heliospheric gas and compared with the polarization calculated for an averaged solar activity. We predict the polarization of charge-exchange X-rays to be between 3% and 8%, depending on the line-of-sight geometry, solar wind ion velocity, and the selected emission lines.
Journal Article•
TL;DR: In this article, the authors analyze the physical implementations of a quantum computer based on polar molecules with switchable dipoles, and propose a switch-able dipole-dipole-based quantum computing system.
Abstract: Resumen en: We analyze recently proposed physical implementations of a quantum computer based on polar molecules with switchable dipoles. Switch- able dipole-dipole ...
Posted Content•
TL;DR: In this paper, the authors report ab initio calculations of the X $^2 \Sigma{u}^+ $ and B $^ 2 \Sigm{g}^+)$ states of the Be$2}+$ dimer, using the aug-cc-pVnZ basis sets.
Abstract: We report ab initio calculations of the X $^2 \Sigma_{u}^+ $ and B $^2 \Sigma_{g}^+$ states of the Be$_{2}^+$ dimer. Full valence configuration interaction calculations were performed using the aug-cc-pVnZ basis sets and the results were extrapolated to the CBS limit. Core-core, core-valence effects are included at the CCSDT/MTsmall level of theory. Two local minima, separated by a large barrier, are found in the expected repulsive B $^2 \Sigma_{g}^+$ state. Spectroscopic constants have been calculated and good agreement is found with the recent measurements of Merritt et al. Bound vibrational levels, transition moments and lifetimes have also been calculated.