Kathy-Anne Brickman

Implementation of Grover's quantum search algorithm in a scalable system

We report the implementation of Grovers quantum search algorithm in the scalable system of trapped atomic ion quantum bits. Any one of four possible states of a two-qubit memory is marked, and following a single query of the search space, the marked element is successfully recovered with an average probability of 60(2)%. This exceeds the performance of any possible classical search algorithm, which can only succeed with a maximum average probability of 50%.

Phase control of trapped ion quantum gates

There are several known schemes for entangling trapped ion quantum bits for large-scale quantum computation. Most are based on an interaction between the ions and external optical fields, coupling internal qubit states of trapped ions to their Coulomb-coupled motion. In this paper, we examine the sensitivity of these motional gate schemes to phase fluctuations introduced through noisy external control fields, and suggest techniques for suppressing the resulting phase decoherence.

Atomic qubit manipulations with an electro-optic modulator

We report new techniques for driving high-fidelity stimulated Raman transitions in trapped-ion qubits. An electro-optic modulator induces sidebands on an optical source, and interference between the sidebands allows coherent Rabi transitions to be efficiently driven between hyperfine ground states separated by 14.53 GHz in a single trapped 111Cd+ ion.

Efficient photoionization loading of trapped ions with ultrafast pulses

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-fs or 1-ps duration at a central wavelength of 229 nm. 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.

Magneto-optical trapping of cadmium

We report the laser cooling and confinement of Cd atoms in a magneto-optical trap and characterize the loading process from the background Cd vapor. The trapping laser drives the {sup 1}S{sub 0}{yields}{sup 1}P{sub 1} transition at 229 nm in this two-electron atom and also photoionizes atoms directly from the {sup 1}P{sub 1} state. This photoionization overwhelms the other loss mechanisms and allows a direct measurement of the photoionization cross section, which we measure to be 2(1)x10{sup -16} cm{sup 2} from the {sup 1}P{sub 1} state. When combined with nearby laser-cooled and trapped Cd{sup +} ions, this apparatus could facilitate studies in ultracold interactions between atoms and ions.

Clean and scalable quantum logic with trapped ions

Summary form only given. Experimental progress in constructing a quantum computer with a collection of trapped ions is discussed, with emphasis on how various technical hurdles may be circumvented.