Magneto-optical trapping of holmium atoms

We demonstrate sub-Doppler laser cooling and magneto-optical trapping of the rare-earth element holmium. Atoms are loaded from an atomic beam source and captured in six-beam sigma(+) - sigma(-) molasses using a strong J = 15/2 <-> J = 17/2 cycling transition at lambda = 410.5 nm. Due to the small difference in hyperfine splittings and Lande g factors in the lower and upper levels of the cooling transition the MOT is self-repumped without additional repump light, and deep sub-Doppler cooling is achieved with the magnetic trap turned on. We measure the leakage out of the cycling transition to metastable states and find a branching ratio <10(-5), which is adequate for state-resolved measurements on hyperfine encoded qubits.