Atomic cadmium ions are loaded into radiofrequency ion traps by photoionization of atoms in a cadmium vapor with ultrafast laser pulses. The photoionization is driven through an intermediate atomic resonance with a frequency-quadrupled mode-locked Ti:sapphire laser that produces pulses of either $100\text{\ensuremath{-}}\mathrm{fs}$ or $1\text{\ensuremath{-}}\mathrm{ps}$ duration at a central wavelength of
229nm. The large bandwidth of the pulses photoionizes all velocity classes of the Cd vapor, resulting in a high loading efficiency compared to previous ion trap loading techniques. Measured loading rates are compared with a simple theoretical model, and we conclude that this technique can potentially ionize every atom traversing the laser beam within the trapping volume. This may allow the operation of ion traps with lower levels of background pressures and less trap electrode surface contamination. The technique and laser system reported here should be applicable to loading most laser-cooled ion species.
All of the essential elements for a trapped ion quantum computer have been demonstrated in previous experiments. There are, however, many technical challenges to scaling the number of quantum bits from the current state-of-the-art (about 8) to the number of qubits needed for practical quantum computing. Although there is experimental evidence supporting one possible method (using cw laser pulses and common motional modes as the ion interaction) for deterministic ion entanglement, it is not known if that will ultimately be the most practical method for building a large-scale quantum computer. One model for scalable quantum computing with trapped ions calls for large interconnected arrays of small traps. Several advancements reported in this work include the development of three layer alumina traps as well as MEMS fabricated microtraps. Other models for scalable trapped ion quantum computing do not call for local entanglement or call for relaxed constraints on the motional control of the ions. These proposals require the use of ultrafast laser pulses interacting with the ions. This work reviews several experiments that explore the interaction between the ultrafast laser and single tripped ions including early indication of ultrafast control and entanglement between a single ion and a single photon frequency qubit.