Date of Award

Spring 1-1-2010

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Neil Ashby

Second Advisor

David W. Wineland

Third Advisor

Konrad Lehnert

Abstract

The quantum states of trapped atomic ions can be highly isolated from external perturbation, and precisely manipulated with applied laser fields. This makes them an excellent medium for quantum-limited experiments such as quantum information processing and precision spectroscopy. A relatively small number of ion species have been used for these types of experiments because most species are difficult to laser cool and detect directly. This thesis demonstrates a way to overcome this limitation by use of sympathetic cooling and state detection based on quantum logic. We apply these techniques to mixed-species arrays of Al+ and Be+ ions. A mathematical model for the motion of such a two-species array is presented in order to explore some features of the ion dynamics that are relevant for the experiments. Repetitive quantum nondemolition measurements of the electronic states of a Al+ ion show detection fidelities as high as 99.94 %. We also demonstrate the simultaneous detection of two Al+ ions and observe a detection fidelity of 99.8 %. The basic ideas behind the detection strategy are extended to potentially enable similar experiments on a more general class of atomic and molecular ions.

We have also investigated, theoretically and experimentally, a method for preparing entangled Dicke states in trapped atomic ions. We consider a linear chain of N ion qubits that is prepared in a particular Fock state of motion. The m phonons are removed by applying a laser pulse globally to the N qubits, and converting the motional excitation to m flipped spins. The global nature of this pulse ensures that the m flipped spins are shared by all the target ions in a state that is a close approximation to the Dicke state.

We calculate numerically the fidelity limits of the protocol and find small deviations from the ideal state for m = 1 and m = 2. We have demonstrated the basic features of this protocol by preparing the Bell state in two Mg+ target ions trapped simultaneously with an Al+ ancillary ion.

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