Showing papers by "Robin Côté published in 2000"
TL;DR: Several schemes for implementing a fast two-qubit quantum gate for neutral atoms with the gate operation time much faster than the time scales associated with the external motion of the atoms in the trapping potential are proposed.
Abstract: We propose several schemes for implementing a fast two-qubit quantum gate for neutral atoms with the gate operation time much faster than the time scales associated with the external motion of the atoms in the trapping potential. In our example, the large interaction energy required to perform fast gate operations is provided by the dipole-dipole interaction of atoms excited to low-lying Rydberg states in constant electric fields. A detailed analysis of imperfections of the gate operation is given.
1,216 citations
TL;DR: In this paper, the authors studied charge transfer and total cross-sections in elastic collisions of atom-ion alkali metals at ultralow temperatures and compared quantal and semiclassical results, and investigated the range of applicability of the Langevin formula.
Abstract: Studies of charge transfer and total cross sections in elastic collisions of atom-ion alkali metals at ultralow temperatures are reported. Calculations for Na+Na{sup +} have been carried out with the best available {sup 2}{sigma}{sub g}{sup +} and {sup 2}{sigma}{sub u}{sup +} potential curves. As functions of energy, the cross sections show considerable structure and are large in the limit of low temperature. The scattering lengths were also computed, and the effective range expansion verified. For higher temperatures, we compare quantal and semiclassical results, and investigate the range of applicability of the Langevin formula. Even at temperatures of a few degrees kelvin, the charge-transfer cross sections are large, and could provide an efficient way to produce cold ions. (c) 2000 The American Physical Society.
183 citations
TL;DR: It is shown that the nature of the charge mobility changes with temperature: at high T, the charges are transported by massive centers (i.e., the ions), and at low T, by electrons jumping from neighboring atoms onto the positive ions (the positive holes exhibit hopping conductivity).
Abstract: Studies of charge mobilities in an ultracold gas are reported. Calculations for the $\mathrm{Na}+{\mathrm{Na}}^{+}$ system have been carried out as a function of temperature $T$ and densities, and the conductivity of the ultracold charged gas is obtained. The total charge mobility exhibits a sharp increase as $T$ is lowered, indicating a transition from an almost insulating to a conducting system at few $\ensuremath{\mu}$K. It is shown that the nature of the charge mobility changes with temperature: at high $T$, the charges are transported by massive centers (i.e., the ions), and at low $T$, by electrons jumping from neighboring atoms onto the positive ions (the positive holes exhibit hopping conductivity). An experiment is proposed to detect this effect.
89 citations
TL;DR: In this article, a second-quantized Hamiltonian was developed to describe photo association, and applied both in the momentum representation and in the position representation (field theory), and the solution of the two-mode problem, including only one mode each for the atomic and molecular condensates, displays analogs of Rabi oscillations and rapid adiabatic passage.
Abstract: We study coherent photoassociation, phenomena analogous to coherent optical transients in few-level systems, which may take place in photoassociation of an atomic Bose-Einstein condensate but not in a nondegenerate gas. We develop a second-quantized Hamiltonian to describe photoassociation, and apply the Hamiltonian both in the momentum representation and in the position representation (field theory). The solution of the two-mode problem, including only one mode each for the atomic and molecular condensates, displays analogs of Rabi oscillations and rapid adiabatic passage. A classical version of the field theory for atoms and molecules is used to demonstrate that, in the presence of photoassociating light, a joint atom-molecule condensate is unstable against the growth of density fluctuations. Experimental complications, including spontaneous emission and unwanted ``rogue'' photodissociation from a photoassociated molecule, are analyzed. A two-color Raman scheme is studied as a method to set up an effective two-mode scheme with reduced spontaneous-emission losses. We discuss photoassociation rates and photoassociation Rabi frequencies for high-lying vibrational states in alkali dimers both on the basis of molecular-structure calculations, and by comparing with an experiment [Wynar et al., Science 287, 1016 (2000)].
52 citations
TL;DR: It is suggested that enhanced cooling of trapped atomic hydrogen by 7Li atoms is feasible and large calculated triplet scattering lengths that are stable against uncertainties in the potential are obtained.
Abstract: We present calculated scattering lengths for collisions between various isotopic forms of lithium and hydrogen atoms interacting via singlet and triplet molecular states of LiH. We demonstrate that one bound triplet level is supported for each isotopomer ${}^{7}\mathrm{LiH}$, ${}^{6}\mathrm{LiH}$, ${}^{7}\mathrm{LiD}$, and ${}^{6}\mathrm{LiD}$. We obtain large calculated triplet scattering lengths that are stable against uncertainties in the potential. We present elastic and momentum transfer cross sections, and the corresponding rate coefficients, for hydrogen atoms colliding with ${}^{7}\mathrm{Li}$ atoms. We suggest that enhanced cooling of trapped atomic hydrogen by ${}^{7}\mathrm{Li}$ atoms is feasible.
36 citations
TL;DR: In this article, the complex interaction potentials arising in the approach of two metastable hydrogen 2s atoms are calculated and the cross sections for ionization, excitation transfer, and elastic scattering are predicted.
Abstract: The complex interaction potentials arising in the approach of two metastable hydrogen 2s atoms are calculated and the cross sections for ionization, excitation transfer, and elastic scattering are predicted. The measured cross section for associative ionization at E = 4.1 meV equals 2x10(-15) cm (2). We calculate a total ionization cross section of 2x10(-13) cm (2), varying as E(-2/3) at higher energies. Thus it appears that dissociative ionization is the major ionization channel. We find also that double excitation transfer into two excited H(2p) atoms is still more probable with the large cross section of 9x10(-12) cm (2) at E = 4.1 meV varying as E(-1/2) at higher energies. The detection of the resulting Lyman alpha photons would provide a diagnostic test of our predictions.
11 citations
TL;DR: In this article, a simplified description of the dynamics of inhomogeneous dilute Bose-Einstein condensates (BECs) is proposed, based on the assumption that the time-evolving BEC preserves its shape (i.e. the density profile remains similar to the initial profile).
Abstract: We discuss a simplified description of the dynamics of inhomogeneous dilute Bose-Einstein condensates (BECs), based on the assumption that the time-evolving BEC preserves its shape (i.e. the density profile remains similar to the initial profile). While the validity of the self-similarity assumption is not a priori obvious, we show that this description becomes exact in the opposite limits of large and small condensates contained by time-dependent spherically symmetric harmonic oscillator trap potentials. We discuss applications of this simple description and we show how the insights derived from it suggest that phase-coherent BECs expanding from optical lattice sites can be used for the purpose of imaging.
8 citations