Non-binary quantum logic with trapped ions

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The prospect of harnessing quantum mechanics to perform new types of computation and to investigate physical phenomena that cannot be tractably modeled in other ways has sparked justifiable excitement over the idea of quantum computers. Nevertheless, practical large-scale quantum computers remain far from our reach, with many orders of magnitude of improvement required of existing hardware before the most-hyped applications can be accomplished. The long-term goal of the research program described in this Discovery Grant application is to increase the informational complexity of attainable quantum processors by developing techniques to store and manipulate information in trapped ion qudits: the multi-state generalization of two-state qubits. The development of practical techniques to manipulate qudits, which encode more information in the same physical device, may present an important shortcut toward the goal of building a large-scale quantum computer. This funding will establish a research program in atomic quantum information science, focusing on tackling initial challenges in the experimental implementation of qudits.Linking many qubits into an algorithm without destroying the information they carry is the primary challenge in quantum computation. One possible way to mitigate this challenge is to use more states per trapped ion (or other physical qubit) to reduce the number of ions required to perform a given algorithm. Despite impressive progress with trapped ion qubits, the use of ions as multi-level qudits remains a mostly hypothetical concept: no experiments have demonstrated all the operations needed to carry out large-scale algorithms based on qudits. We propose to investigate these building-block operations, such as how to carry out logic gates on single qudits or entangle pairs of qudits, or how to reliably read out the result of a computation. These initial studies are needed to assess the practical promise of the approach, but the results of these investigations are hoped to eventually seed the development of a quantum processor which uses multi-state ions to attain more computational power than if it had used only two states per ion. The experimental advances and theoretical understanding developed through this research program will have lasting impact on our ability to harness quantum mechanics to complement conventional computing capabilities. This proposal requests funding for the salaries of the undergraduate, graduate, and postdoctoral researchers who will carry out the experiments, along with funding for their travel to scientific conferences, supplies and equipment for their experiments, and costs associated with publishing results. This will benefit Canada by funding the training of various highly-qualified personnel who will develop the skills and expertise necessary to contribute to tomorrow's quantum technologies.