We present our experimental setup to produce ultracold strongly correlated fermionic superfluids ... more We present our experimental setup to produce ultracold strongly correlated fermionic superfluids made of a two-component spin-mixture of 6Li atoms. Employing standard cooling techniques, we achieve quantum degeneracy in a single-beam optical dipole trap. Our setup is capable of generating spin-balanced samples at temperatures as low as T/TF = 0.1 containing up to 5 × 10^4 atomic pairs. We can access different superfluid regimes by tuning the interparticle interactions close to a broad magnetic Feshbach resonance. In particular, we are able to explore the crossover from the molecular Bose-Einstein condensate (BEC) to the Bardeen-Cooper-Schrieffer (BCS) superfluid regimes. In the near future, we plan to study different collective excitations in these superfluid samples.
We study the quantum description of energy fluctuations induced by stochastic changes in the freq... more We study the quantum description of energy fluctuations induced by stochastic changes in the frequency of atom traps. Using the connection between classical and quantum descriptions of parametric oscillators, the classical cumulant expansion method is used to obtain quantum results beyond standard perturbation theory. Both the case of static and time-dependent traps are explicitly worked out
We present our recently-built experimental setup designed to generate near-infrared and narrow-ba... more We present our recently-built experimental setup designed to generate near-infrared and narrow-band correlated photon pairs by inducingfour-wave mixing in a cold gas of 87Rb atoms confined in a magneto-optical trap. The experimental setup and its automation and control approach are described in detail. A characterization of the optical density of the atomic ensemble as well as the basic statistical measurements of the generated light are reported. The non-classical nature of the photons pairs is confirmed by observing a violation of Cauchy-Schwarz inequality by a factor of 5.6 × 10 5 in a Hanbury Brown – Twiss interferometer. A 1/e coherence time for the heralded, idler photons of 4.4 ± 0.1 ns is estimated from our observations. We are able to achieve a value of 104 s−1pair-detection-rate, which results in a spectral brightness of 280 (MHz s)−1. The combination of high brightness and narrow-band spectrum makes this photon-pair source a viable tool in fundamental studies of quantum s...
An advanced undergraduate experiment to study the 5P 3=2 ! 6P 3=2 electric quadrupole transition ... more An advanced undergraduate experiment to study the 5P 3=2 ! 6P 3=2 electric quadrupole transition in rubidium atoms is presented. The experiment uses two external cavity diode lasers, one operating at the D2 rubidium resonance line and the other built with commercial parts to emit at 911 nm. The lasers produce the 5s ! 5p ! 6p excitation sequence in which the second step is the forbidden transition. Production of atoms in the 6P 3=2 state is observed by detection of the 420 nm fluorescence that results from electric dipole decay into the ground state. Lines whose widths are significantly narrower than the Doppler width are used to study the hyperfine structure of the 6P 3=2 state in rubidium. The spectra illustrate characteristics unique to electric dipole forbidden transitions, like the electric quadrupole selection rules; they are also used to show general aspects of two-color laser spectroscopy such as velocity selection and hyperfine pumping. V
DNA curvature plays a well-characterized role in many transcriptional regulation mechanisms. We p... more DNA curvature plays a well-characterized role in many transcriptional regulation mechanisms. We present evidence for the conservation of curvature signals in putative regulatory regions of several archaeal and eubacterial genomes. Genes with highly curved upstream regions were identi®ed in orthologous groups, based on the annotations of the Cluster of Orthologous Groups of proteins (COG) database. COGs possessing a signi®cant number of genes with curvature signals were analyzed, and conserved properties were found in several cases. Curvature signals related to regulatory sites, previously described in single organisms, were located in a broad spectrum of bacterial genomes. Global regulatory proteins, such as HU, IHF and FIS, known to bind to curved DNA and to be autoregulated, were found to present conserved DNA curvature signals in their regulatory regions, emphasizing the fact that structural parameters of the DNA molecule are conserved elements in the process of transcriptional regulation of some systems. It is currently an open question whether these diverse systems are part of an integrated global regulatory response in different microorganisms.
Abstract Friendly software is defined as computer programs which can be run interactively and pro... more Abstract Friendly software is defined as computer programs which can be run interactively and profitably without incurring fatal errors causing execution termination. We discuss a modular library and a simple program structure providing for input validation, help, status, ...
Taking into account the characteristics of a free scalar field in elliptic coordinates, a new dyn... more Taking into account the characteristics of a free scalar field in elliptic coordinates, a new dynamical variable is found for the free electromagnetic field. The conservation law associated to this variable cannot be obtained by direct application of standard Noether theorem since the symmetry generator is of second order. Consequences on the expected mechanical behavior of an atomic system interacting with electromagnetic waves exhibiting such a symmetry are also discussed.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2010
We provide an efficient form to express the action of a many-body Hamiltonian of harmonically tra... more We provide an efficient form to express the action of a many-body Hamiltonian of harmonically trapped interacting Fermi particles on wavefunctions built from paired states. The expression is suitable to numerically determine the ground state energy, regardless of the form of the two-body interaction. It takes advantage of the knowledge of the two-particle problem and the inherent properties of the
ABSTRACT We present a full vectorial analysis of the parametric downconversion process using a pu... more ABSTRACT We present a full vectorial analysis of the parametric downconversion process using a pump Bessel beam and a photon description based on Bessel wavefunctions. We find that, under the considered geometry, optical angular momentum is conserved but the crystal induces a coupling between the optical spin angular momentum (SAM) and the optical orbital angular momentum (OAM) ruled by the nonlinear properties of the crystal via the second order susceptibility tensor χijk(2). This leads to nontrivial correlations between the expected values of the SAM and OAM of the resulting two-photon states. Distributions of orbital angular momentum of the downconverted photons are evaluated in detail for a specific set-up.
A canon~cal formalism obtained for path-dependent Lagrangians is applied to Fokker-type Lagrangta... more A canon~cal formalism obtained for path-dependent Lagrangians is applied to Fokker-type Lagrangtans. The results are specialized for coupling constant expansions and later on are applied to relativistic systems of particles interacting through symmetric scalar and vector mesodynamics and electrodynamics.
A theoretical analysis of binary collisions of quantum droplets under feasible experimental condi... more A theoretical analysis of binary collisions of quantum droplets under feasible experimental conditions is reported. Droplets formed from degenerate dilute Bose gases made up from binary mixtures of ultracold atoms are considered. Reliable expressions for the surface tension of the droplets are introduced based on a study of low energy excitations of their ground state within the random phase approximation. Their relevance is evaluated considering an estimation of the expected excitation energy having in mind the Thouless variational theorem. The surface tension expressions allow calculating the Weber number of the droplets involved in the collisions. Several regimes on the outcomes of the binary frontal collisions that range from the coalescence of the quantum droplets to their disintegration into smaller droplets are identified. Atoms losses of the droplets derived from self-evaporation and three-body scattering are quantified for both homo- and hetero-nuclear mixtures. Their contr...
We present our experimental setup to produce ultracold strongly correlated fermionic superfluids ... more We present our experimental setup to produce ultracold strongly correlated fermionic superfluids made of a two-component spin-mixture of 6Li atoms. Employing standard cooling techniques, we achieve quantum degeneracy in a single-beam optical dipole trap. Our setup is capable of generating spin-balanced samples at temperatures as low as T/TF = 0.1 containing up to 5 × 10^4 atomic pairs. We can access different superfluid regimes by tuning the interparticle interactions close to a broad magnetic Feshbach resonance. In particular, we are able to explore the crossover from the molecular Bose-Einstein condensate (BEC) to the Bardeen-Cooper-Schrieffer (BCS) superfluid regimes. In the near future, we plan to study different collective excitations in these superfluid samples.
We study the quantum description of energy fluctuations induced by stochastic changes in the freq... more We study the quantum description of energy fluctuations induced by stochastic changes in the frequency of atom traps. Using the connection between classical and quantum descriptions of parametric oscillators, the classical cumulant expansion method is used to obtain quantum results beyond standard perturbation theory. Both the case of static and time-dependent traps are explicitly worked out
We present our recently-built experimental setup designed to generate near-infrared and narrow-ba... more We present our recently-built experimental setup designed to generate near-infrared and narrow-band correlated photon pairs by inducingfour-wave mixing in a cold gas of 87Rb atoms confined in a magneto-optical trap. The experimental setup and its automation and control approach are described in detail. A characterization of the optical density of the atomic ensemble as well as the basic statistical measurements of the generated light are reported. The non-classical nature of the photons pairs is confirmed by observing a violation of Cauchy-Schwarz inequality by a factor of 5.6 × 10 5 in a Hanbury Brown – Twiss interferometer. A 1/e coherence time for the heralded, idler photons of 4.4 ± 0.1 ns is estimated from our observations. We are able to achieve a value of 104 s−1pair-detection-rate, which results in a spectral brightness of 280 (MHz s)−1. The combination of high brightness and narrow-band spectrum makes this photon-pair source a viable tool in fundamental studies of quantum s...
An advanced undergraduate experiment to study the 5P 3=2 ! 6P 3=2 electric quadrupole transition ... more An advanced undergraduate experiment to study the 5P 3=2 ! 6P 3=2 electric quadrupole transition in rubidium atoms is presented. The experiment uses two external cavity diode lasers, one operating at the D2 rubidium resonance line and the other built with commercial parts to emit at 911 nm. The lasers produce the 5s ! 5p ! 6p excitation sequence in which the second step is the forbidden transition. Production of atoms in the 6P 3=2 state is observed by detection of the 420 nm fluorescence that results from electric dipole decay into the ground state. Lines whose widths are significantly narrower than the Doppler width are used to study the hyperfine structure of the 6P 3=2 state in rubidium. The spectra illustrate characteristics unique to electric dipole forbidden transitions, like the electric quadrupole selection rules; they are also used to show general aspects of two-color laser spectroscopy such as velocity selection and hyperfine pumping. V
DNA curvature plays a well-characterized role in many transcriptional regulation mechanisms. We p... more DNA curvature plays a well-characterized role in many transcriptional regulation mechanisms. We present evidence for the conservation of curvature signals in putative regulatory regions of several archaeal and eubacterial genomes. Genes with highly curved upstream regions were identi®ed in orthologous groups, based on the annotations of the Cluster of Orthologous Groups of proteins (COG) database. COGs possessing a signi®cant number of genes with curvature signals were analyzed, and conserved properties were found in several cases. Curvature signals related to regulatory sites, previously described in single organisms, were located in a broad spectrum of bacterial genomes. Global regulatory proteins, such as HU, IHF and FIS, known to bind to curved DNA and to be autoregulated, were found to present conserved DNA curvature signals in their regulatory regions, emphasizing the fact that structural parameters of the DNA molecule are conserved elements in the process of transcriptional regulation of some systems. It is currently an open question whether these diverse systems are part of an integrated global regulatory response in different microorganisms.
Abstract Friendly software is defined as computer programs which can be run interactively and pro... more Abstract Friendly software is defined as computer programs which can be run interactively and profitably without incurring fatal errors causing execution termination. We discuss a modular library and a simple program structure providing for input validation, help, status, ...
Taking into account the characteristics of a free scalar field in elliptic coordinates, a new dyn... more Taking into account the characteristics of a free scalar field in elliptic coordinates, a new dynamical variable is found for the free electromagnetic field. The conservation law associated to this variable cannot be obtained by direct application of standard Noether theorem since the symmetry generator is of second order. Consequences on the expected mechanical behavior of an atomic system interacting with electromagnetic waves exhibiting such a symmetry are also discussed.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2010
We provide an efficient form to express the action of a many-body Hamiltonian of harmonically tra... more We provide an efficient form to express the action of a many-body Hamiltonian of harmonically trapped interacting Fermi particles on wavefunctions built from paired states. The expression is suitable to numerically determine the ground state energy, regardless of the form of the two-body interaction. It takes advantage of the knowledge of the two-particle problem and the inherent properties of the
ABSTRACT We present a full vectorial analysis of the parametric downconversion process using a pu... more ABSTRACT We present a full vectorial analysis of the parametric downconversion process using a pump Bessel beam and a photon description based on Bessel wavefunctions. We find that, under the considered geometry, optical angular momentum is conserved but the crystal induces a coupling between the optical spin angular momentum (SAM) and the optical orbital angular momentum (OAM) ruled by the nonlinear properties of the crystal via the second order susceptibility tensor χijk(2). This leads to nontrivial correlations between the expected values of the SAM and OAM of the resulting two-photon states. Distributions of orbital angular momentum of the downconverted photons are evaluated in detail for a specific set-up.
A canon~cal formalism obtained for path-dependent Lagrangians is applied to Fokker-type Lagrangta... more A canon~cal formalism obtained for path-dependent Lagrangians is applied to Fokker-type Lagrangtans. The results are specialized for coupling constant expansions and later on are applied to relativistic systems of particles interacting through symmetric scalar and vector mesodynamics and electrodynamics.
A theoretical analysis of binary collisions of quantum droplets under feasible experimental condi... more A theoretical analysis of binary collisions of quantum droplets under feasible experimental conditions is reported. Droplets formed from degenerate dilute Bose gases made up from binary mixtures of ultracold atoms are considered. Reliable expressions for the surface tension of the droplets are introduced based on a study of low energy excitations of their ground state within the random phase approximation. Their relevance is evaluated considering an estimation of the expected excitation energy having in mind the Thouless variational theorem. The surface tension expressions allow calculating the Weber number of the droplets involved in the collisions. Several regimes on the outcomes of the binary frontal collisions that range from the coalescence of the quantum droplets to their disintegration into smaller droplets are identified. Atoms losses of the droplets derived from self-evaporation and three-body scattering are quantified for both homo- and hetero-nuclear mixtures. Their contr...
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Papers by R. Jáuregui