Ultracold Polar KRb Molecules in Optical Lattices

The creation of a gas of ultracold polar molecules with a high phase space density brings new possibilities beyond experiments with ultracold atomic gases. In particular, long-range, anisotropic, and tunable dipole-dipole interactions open the way for novel quantum gases, with applications including strongly correlated many-body systems, and ultracold chemistry. This thesis will present the final steps to complete control over both internal and external degrees of freedom of the molecule which allows us to control, and even completely suppress, the chemical reactions between molecules. First, the control over internal states has been achieved through coherent state transfer to the ro-vibronic ground state and coherent manipulations of the hyperfine and rotational states with microwave radiation. Second, external degrees of freedom are controlled by loading the gas into an optical lattice. With the molecules loaded into a one-dimensional lattice, the orientation of the molecular collisions is controlled by manipulating both internal (hyperfine states) and external (motional states in the direction of tight confinement) degrees of freedom. Most striking is that by preparing the molecules all in the lowest band of the lattice in the same internal state, the molecular collisions can only occur in a side-by-side" orientation, where the chemical reaction rate is suppressed by the repulsive dipole-dipole interactions. The chemical reaction can be suppressed completely by further constraining the motion in the trap in a strong 3D lattice. Here we see lifetimes longer than 20 s, limited by o-resonant light scattering. Finally, the ac polarizability of the molecules is explored and controlled. The different rotational states of the molecule have different polarizabilities and will experience a different trapping force in both the optical dipole trap or lattice. We show that there is a magic angle" between the quantization axis and the polarization of the trapping laser at which the polarizabilities of two different rotational states can be matched, eliminating dephasing and allowing for coherent manipulations between rotational states

A High Temperature Calcium Vapor Cell for Spectroscopy on the 4s^2 1S0 to 4s4p 3P1 Intercombination Line

We have demonstrated a high temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high temperature vacuum valves and glass-to-metal seals. We have observed over 50 percent absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the broadening resulted in higher signal-to-noise ratios by allowing us to probe the atoms with intensities much greater than the 0.2 uW/cm^2 saturation intensity of the unbroadened transition.Comment: 5 pages, 2 figures, submitted to Rev. Sci. Instru

Observation of prethermalization in long-range interacting spin chains

Although statistical mechanics describes thermal equilibrium states, these states may or may not emerge dynamically for a subsystem of an isolated quantum many-body system. For instance, quantum systems that are near-integrable usually fail to thermalize in an experimentally realistic time scale, and instead relax to quasi-stationary prethermal states that can be described by statistical mechanics, when approximately conserved quantities are included in a generalized Gibbs ensemble (GGE). We experimentally study the relaxation dynamics of a chain of up to 22 spins evolving under a long-range transverse-field Ising Hamiltonian following a sudden quench. For sufficiently long-range interactions, the system relaxes to a new type of prethermal state that retains a strong memory of the initial conditions. However, the prethermal state in this case cannot be described by a standard GGE; it rather arises from an emergent double-well potential felt by the spin excitations. This result shows that prethermalization occurs in a broader context than previously thought, and reveals new challenges for a generic understanding of the thermalization of quantum systems, particularly in the presence of long-range interactions