Session C6: BEC and Atom Interferometry

Spatial Dependence of Entropy in Trapped Ultracold Bose Gases

We find a new physical regime in the trapped Bose-Hubbard Hamiltonian using time-evolving block decimation. Between Mott-insulating and superfluid phases, the latter induced by trap compression, a spatially self-organized state appears in which non-local entropy signals entanglement between spatially distant superfluid shells. We suggest a linear rather than harmonic potential as an ideal way to observe such a self-organized system. We also explore both quantum information and thermal entropies in the superfluid regime, finding that while the former follows the density closely the latter can be strongly manipulated with the mean field.   

Nonlinear Scattering of BECs on a Finite Barrier

We consider the scattering of a Bose-Einstein condensate (BEC) on a finite barrier. The nonlinear Schr\"{o}dinger equation (NLS) models the mean field of a BEC. The nonlinearity gives rise to several interesting physical and mathematical features which are not present in the linear problem. We present density and transmission plots for several physical cases, along with a discussion of these novel features. We also use the theory to model recent experiments.   

p-Wave Resonant Bose Gas: A Finite-Momentum Spinor Superfluid

We study a degenerate gas of two-species bosonic atoms interacting through a $p$-wave Feshbach resonance (as realized in, e.g., a $^{85}$Rb-$^{87}$Rb mixture). We show that this model exhibits a finite-momentum atomic-molecular superfluid (AMSF), sandwiched by a molecular $p$-wave (orbital spinor) superfluid and by an $s$-wave atomic superfluid at large negative and positive detunings, respectively. The magnetic field can be used to tune the modulation wave vector of the AMSF state, as well as to drive quantum phase transitions in this rich system.   

Calculation of Feshbach Resonances with Rb-85 Atoms Using Realistic Potentials to Constrain Separable Potentials

The phenomenology of Feshbach resonances in cold quantum gases has been studied with Rb-85 atoms in the presence of an external magnetic field. For a pair of such atoms interacting with a particular magnetic field value, various separable potential models have been utilized to calculate the singlet and triplet scattering lengths and corresponding strength parameters from fitted dipole form factors. Such calculations are extended to incorporate more realistic potential models in order to constrain separable potentials applicable to the 3- body interaction. Unitary pole expansion approximations are explored in the attempt to extract the particular atomic states contributing to the Feshbach resonance from spectral decompositions of such realistic potentials. A full 2-body calculation of Rb-85 atoms is to be presented in position- space, from which 3-body calculations in momentum-space can be done in order to study the phenomenon of 3-body recombination and breakup processes in cold quantum gases.   

A Slow Ion Strontium Interferometer

I will discuss an interferometer centered around a laser-cooled source of $^{87}$Sr$^+$ ions, which will be split and recombined using stimulated Raman transitions. This will take place inside a conducting cylinder allowing the interferometer to measure electric and magnetic fields with unprecedented precision. Practical applications for the device include the precision measurement of the evolution of fields near solids to reveal their electronic structure. It will also be used for fundamental tests of the basic laws of electromagnetism and the search for a non-zero photon rest mass. The device should detect possible photon rest mass more than 100 times smaller than previous laboratory experiments. Both the details of the device and the theory connecting deviations from Coulomb's inverse-square law to a theory of massive photons will be discussed.   

Optical Feshbach Resonances in Alkaline Earth Atoms

Recent proposals have shown that a quantum degenerate gas of alkaline earth atoms can be used for a number of novel quantum computing and quantum simulation experiments. Strontium is a good candidate for such experiments because it can be controlled with high precision, as demonstrated in recent atomic clock experiments. Unfortunately, the small scattering length of strontium is not amenable to evaporative cooling techniques that are used to reach quantum degeneracy. Furthermore, increasing the scattering length of alkaline earths with a magnetic Feshbach resonance is not possible due to their spinless electronic ground state configuration. However, recent theoretical and experimental work suggests the possibility of changing scattering lengths in alkaline earths with laser light. Using this optical Feshbach resonance near strontium's narrow $^{1}S_{0} \rightarrow ^{3}P_{1}$ intercombination transition might allow its scattering length to be controlled without significant atom loss. We report our recent progress in demonstrating an optical Feshbach resonance in strontium 88.