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We report on accurate measurements of the hyperfine constants of the narrow cooling transition of neutral Holmium at 412.1 nm. This transition has a linewidth of 2.3 MHz and a Doppler temperature of 55 microK which renders it suitable for second stage laser cooling. The proximity of the wavelength to the strong cooling transition at 410.5 nm[1] renders this transition convenient for first and second stage cooling using a combined optical setup. The hyperfine constants were measured using Doppler free saturated absorption spectroscopy in a hollow cathode discharge. Relative measurements of the locations of the hyperfine levels were made using an EOM modulator with an RF offset relative to a stable ULE cavity reference. The A and B hyperfine constants were determined to be A= 715.85±0.15 MHz and B= 1013±16.0 MHz which significantly improves on the precision of earlier measurements. 

Optically trapped neutral atoms are one of several leading approaches for scalable quantum information processing. When prepared in electronic ground states in deep optical lattices atomic qubits are weakly interacting with long coherence times. Excitation to Rydberg states turns on strong interactions which enable fast gates and entanglement generation. I will present quantum logic experiments with a 2D array of blue detuned lines that traps more than 100 Cesium atom qubits. The array is randomly loaded from a MOT and an optical tweezer steered by a 2D acousto-optic deflector is used to ll subregions of the array. Progress towards high fidelity entangling gates based on Rydberg excitation lasers with lower noise, and optimized optical polarization and magnetic eld settings will be shown. 

Neutral Holmium′s 128 ground hyperfine states, the most of any non-radioactive element, is a testbed for quantum control of a very high dimensional Hilbert space, and offers a promising platform for quantum computing. Its high magnetic moment also makes magnetic trapping a potentially viable alternative to optical trapping. Previously we have cooled Holmium atoms in a MOT on a 410.5 nm transition, characterized its Rydberg spectra, and made measurements of the dynamic scalar and tensor polarizabilities. We report here on progress towards narrow line cooling and magnetic trapping of single atoms. 

Theory for one and two atom interactions is developed for the case when the atoms have a Rydberg electron attached to a hyper- fine split core state, a situation relevant for some rare earth and some alkaline earth atoms proposed for experiments on Rydberg-Rydberg in- teractions. For the rare earth atoms, the core electrons can have a very substantial total angular momentum, J, and a non-zero nuclear spin, I. For alkaline earth atoms there is a single, s, core electron whose spin can couple to a non-zero nuclear spin for odd isotopes. The hyperfine splitting of the core state can lead to substantial mixing between the Rydberg series attached to different thresholds. Compared to the un- perturbed Rydberg series of the alkali atoms, series perturbations and near degeneracies from the different parity states could lead to quali- tatively different behavior for single atom Rydberg properties (polariz- ability, Zeeman mixing and splitting, etc) as well as Rydberg-Rydberg interactions (C5 and C6 matrices). 

Neutral Holmiums 128 ground hyperfine states, the most of any non-radioactive element, is a test bed for quantum con- trol of a very high dimensional Hilbert space, and offers a promising platform for quantum computing. Previously we have cooled Holmium atoms in a MOT on a 410.5 nm transition and characterized its Ry- dberg spectra. We report here on the first optical dipole trapping of Holmium with a 532 nm wavelength trap laser. The trap lifetime is close to 1 sec., limited by photon scattering from nearby transitions. The trapped atoms are used to measure the dynamic scalar and tensor polarizabilities which are compared with calculations based on measured oscillator strengths. We also report progress towards narrow line cooling and magnetic trapping of single atoms.