Rydberg-Rydberg interaction profile from the excitation dynamics of ultracold atoms in lattices

We propose a method for the determination of the interaction potential of Rydberg atoms. Specifically, we consider a laser-driven Rydberg gas confined in a one-dimensional lattice and demonstrate that the Rydberg atom number after a laser excitation cycle as a function of the laser detuning provides a measure for the Rydberg interaction coefficient. With the lattice spacing precisely known, the proposed scheme only relies on the measurement of the number of Rydberg atoms and thus circumvents the necessity to map the interaction potential by varying the interparticle separation.Comment: 4 pages, 2 figure

Statistical Aspects of Ultracold Resonant Scattering

Compared to purely atomic collisions, ultracold collisions involving molecules have the potential to support a much larger number of Fano-Feshbach resonances due to the huge amount of ro-vibrational states available. In order to handle such ultracold atom-molecule collisions, we formulate a theory that incorporates the ro-vibrational Fano-Feshbach resonances in a statistical manner while treating the physics of the long-range scattering, which is sensitive to such things as hyperfine states, collision energy and any applied electromagnetic fields, exactly within multichannel quantum defect theory. Uniting these two techniques, we can assess the influence of highly resonant scattering in the threshold regime, and in particular its dependence on the hyperfine state selected for the collision. This allows us to explore the onset of Ericson fluctuations in the regime of overlapping resonances, which are well-known in nuclear physics but completely unexplored in the ultracold domain.Comment: 16 pages, 7 figure

Spectra and ground states of one- and two-dimensional laser-driven lattices of ultracold Rydberg atoms

We investigate static properties of laser-driven, ultracold Rydberg atoms confined to one- and two-dimensional uniform lattices in the limit of vanishing laser coupling. The spectral structure of square lattices is compared to those of linear chains and similarities as well as differences are pointed out. Furthermore, we employ a method based on elements of graph theory to numerically determine the laser detuning-dependent ground states of various lattice geometries. Ground states for chains as well as square and rectangular lattices are provided and discussed.Comment: 15 pages, 11 Figure

One-dimensional Rydberg Gas in a Magnetoelectric Trap

We study the quantum properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap which is superimposed by a homogeneous electric field. Trapped Rydberg atoms can be created in long-lived electronic states exhibiting a permanent electric dipole moment of several hundred Debye. The resulting dipole-dipole interaction in conjunction with the radial confinement is demonstrated to give rise to an effectively one-dimensional ultracold Rydberg gas with a macroscopic interparticle distance. We derive analytical expressions for the electric dipole moment and the critical linear density of Rydberg atoms.Comment: 4 pages, 2 figure

Spectral properties of finite laser-driven lattices of ultracold Rydberg atoms

We investigate the spectral properties of a finite laser-driven lattice of ultracold Rydberg atoms exploiting the dipole blockade effect in the frozen Rydberg gas regime. Uniform one-dimensional lattices as well as lattices with variable spacings are considered. In the case of a weak laser coupling, we find a multitude of many-body Rydberg states with well-defined excitation properties which are adiabatically accessible starting from the ground state. A comprehensive analysis of the degeneracies of the spectrum as well as of the single and pair excitations numbers of the eigenstates is performed. In the strong laser regime, analytical solutions for the pseudo-fermionic eigenmodes are derived. Perturbative energy corrections for this approximative approach are provided.Comment: 17 pages, 12 figure

Dressing of Ultracold Atoms by their Rydberg States in a Ioffe-Pritchard Trap

We explore how the extraordinary properties of Rydberg atoms can be employed to impact the motion of ultracold ground state atoms. Specifically, we use an off-resonant two-photon laser dressing to map features of the Rydberg states on ground state atoms. It is demonstrated that the interplay between the spatially varying quantization axis of the considered Ioffe-Pritchard field and the fixed polarizations of the laser transitions provides the possibility of substantially manipulating the ground state trapping potential.Comment: 11 pages, 4 figure

A Fresh Look at Axions and SN 1987A

We re-examine the very stringent limits on the axion mass based on the strength and duration of the neutrino signal from SN 1987A, in the light of new measurements of the axial-vector coupling strength of nucleons, possible suppression of axion emission due to many-body effects, and additional emission processes involving pions. The suppression of axion emission due to nucleon spin fluctuations induced by many-body effects degrades previous limits by a factor of about 2. Emission processes involving thermal pions can strengthen the limits by a factor of 3-4 within a perturbative treatment that neglects saturation of nucleon spin fluctuations. Inclusion of saturation effects, however, tends to make the limits less dependent on pion abundances. The resulting axion mass limit also depends on the precise couplings of the axion and ranges from 0.5x10**(-3) eV to 6x10**(-3) eV.Comment: 32 latex pages, 13 postscript figures included, uses revtex.sty, submitted to Physical Review

Ultracold Rydberg Atoms in a Ioffe-Pritchard Trap : Creating One-Dimensional Rydberg Gases and Exploiting their Composite Character

Subject of this thesis is the theoretical study of the quantum properties of ultracold Rydberg atoms in the presence of inhomogeneous external fields. Using the Ioffe-Pritchard configuration as a key ingredient superimposed by a homogeneous electric field, we demonstrate that trapped Rydberg atoms can be created in long-lived circular states exhibiting a permanent electric dipole moment of several hundred Debye. The resulting dipole-dipole interaction in conjunction with the radial confinement is demonstrated to entail an effectively one-dimensional Rydberg gas with a macroscopic interparticle distance. Turning our investigations to the low angular momentum electronic states, we demonstrate that the two-body character of Rydberg atoms significantly alters their trapping properties opposed to point-like particles with identical magnetic moment. Analytical expressions describing the resulting trapping potentials are derived and their validity is confirmed by comparison with the numerical solutions of the underlying Schrödinger equation. The center of mass dynamics are studied by means of an adiabatic approach and implications for quantum information protocols involving magnetically trapped Rydberg atoms are discussed. We conclude by demonstrating how the specific signatures of the Rydberg trapping potential can be probed by means of ground state atoms that are off-resonantly coupled to the Rydberg state via a two-photon laser transition