Jennie Guzman

Ultracold Atoms in a Tunable Optical Kagome Lattice

We realize a two-dimensional kagome lattice for ultracold atoms by overlaying two commensurate triangular optical lattices generated by light at the wavelengths of 532 and 1064 nm. Stabilizing and tuning the relative position of the two lattices, we explore different lattice geometries including a kagome, a one-dimensional stripe, and a decorated triangular lattice. We characterize these geometries using Kapitza-Dirac diffraction and by analyzing the Bloch-state composition of a superfluid released suddenly from the lattice. The Bloch-state analysis also allows us to determine the ground-state distribution within the superlattice unit cell. The lattices implemented in this work offer a near-ideal realization of a paradigmatic model of many-body quantum physics, which can serve as a platform for future studies of geometric frustration.

High-resolution magnetometry with a spinor Bose-Einstein condensate.

We demonstrate a precise magnetic microscope based on direct imaging of the Larmor precession of a 87Rb spinor Bose-Einstein condensate. This magnetometer attains a field sensitivity of 8.3 pT/Hz1/2 over a measurement area of 120 microm2, an improvement over the low-frequency field sensitivity of modern SQUID magnetometers. The achieved phase sensitivity is close to the atom shot-noise limit, estimated as 0.15 pT/Hz1/2 for a unity duty cycle measurement, suggesting the possibilities of spatially resolved spin-squeezed magnetometry. This magnetometer marks a significant application of degenerate atomic gases to metrology.

Spontaneously modulated spin textures in a dipolar spinor Bose-Einstein condensate

Helical spin textures in a 87Rb F=1 spinor Bose-Einstein condensate are found to decay spontaneously toward a spatially modulated structure of spin domains. The formation of this modulated phase is ascribed to magnetic dipolar interactions that energetically favor the short-wavelength domains over the long-wavelength spin helix. The reduction of dipolar interactions by a sequence of rf pulses results in a suppression of the modulated phase, thereby confirming the role of dipolar interactions in this process. This study demonstrates the significance of magnetic dipole interactions in degenerate 87Rb F=1 spinor gases.

Amplification of Fluctuations in a Spinor Bose Einstein Condensate

densate are used as an amplifier of quantum spin fluctuations. We demonstrate the spectrum of this amplifier to be tunable, in quantitative agreement with mean-field calculations. We quantify the microscopic spin fluctuations of the initially paramagnetic condensate by applying this amplifier and measuring the resulting macroscopic magnetization. The magnitude of these fluctuations is consistent with predictions of a beyond-mean-field theory. The spinor-condensate-based spin amplifier is thus shown to be nearly quantum-limited at a gain as high as 30 dB. Accompanied by a precise theoretical framework and created in the lab in a highly controlled manner, ultracold atomic systems serve as a platform for studies of quantum dynamics and many-body quantum phases. Among these systems, gaseous spinor Bose Einstein condensates [1, 2, 3, 4, 5], in which atoms may explore all sub-levels of a non-zero hyperfine spin F, provide a compelling opportunity to access the static and dynamical properties of a magnetic superfluid [6, 7, 8, 9, 10]. We previously identified a quantum phase transition in an F = 1 spinor Bose Einstein condensate between a paramagnetic and ferromagnetic phase [9]. This transition is crossed as the quadratic Zeeman energy term, of

Periodic spin textures in a degenerate F=1 87Rb spinor Bose gas

We report on the spin textures produced by cooling unmagnetized

Nonlinear magneto-optical rotation and Zeeman and hyperfine relaxation of potassium atoms in a paraffin-coated cell

^{87}\mathrm{Rb}

Long-time-scale dynamics of spin textures in a degenerate F=187Rb spinor Bose gas

F=1

Mean-field scaling of the superfluid to Mott insulator transition in a 2D optical superlattice

spinor gases into the regime of quantum degeneracy. At low temperatures, magnetized textures form that break translational symmetry and display short-range periodic magnetic order characterized by one- or two-dimensional spatial modulations with wavelengths much smaller than the extent of the quasi-two-dimensional degenerate gas. Spin textures produced upon cooling spin mixtures with a nonzero initial magnetic quadrupole moment also show ferromagnetic order that, at low temperature, coexists with the spatially modulated structure.

Search for Violations of Bose-Einstein Statistics Using Ultra-Cold Sr Atoms

Nonlinear magneto-optical Faraday rotation (NMOR) on the potassium D1 and D2 lines was used to study Zeeman relaxation rates in an antirelaxation paraffin-coated 3-cm-diameter potassium vapor cell. Intrinsic Zeeman relaxation rates of {gamma}{sup NMOR}/2{pi}=2.0(6) Hz were observed. The relatively small hyperfine intervals in potassium lead to significant differences in NMOR in potassium compared to rubidium and cesium. Using laser optical pumping, widths and frequency shifts were also determined for transitions between ground-state hyperfine sublevels of {sup 39}K atoms contained in the same paraffin-coated cell. The intrinsic hyperfine relaxation rate of {gamma}{sub expt}{sup hf}/2{pi}=10.6(7) Hz and a shift of -9.1(2) Hz were observed. These results show that adiabatic relaxation gives only a small contribution to the overall hyperfine relaxation in the case of potassium, and the relaxation is dominated by other mechanisms similar to those observed in previous studies with rubidium.