Integrated chips and optical cavities for trapped ion quantum information processing

Abstract

Quantum information processing is a new and exciting field which uses quantum mechanical systems to perform information processing. At the heart of the excitement are quantum computation - which promises efficient algorithms for simulating physical systems, factoring, and searching unsorted databases - and quantum communication - which provides a provably secure communications protocol. Trapped ions show much promise for achieving large-scale quantum information processing. Experiments thus far have demonstrated small algorithms and entanglement of two remote ions. Current work focuses on scaling to large numbers of ions for quantum computation and interconversion between trapped ions and photons for quantum communication. This thesis addresses some of the challenges facing scaling and interconversion for trapped ion quantum information processing. The first part of the thesis describes the development of scalable, multiplexed ion trap chips for quantum computation. The ion trap chips are based on a new ion trap geometry, called the surface-electrode trap, in which all of the electrodes reside in a single plane. Three generations of surface-electrode traps are designed, fabricated, and tested - culminating with the demonstration of an ion trap chip microfabricated using standard silicon VLSI materials and processes for scalability to small trap size and large arrays of interconnected ion traps. The second part of the thesis presents an experiment that demonstrates cavity cooling, a method of laser cooling the motional state of trapped ions without decohering the internal qubit state.

(cont.) Cavity cooling is demonstrated for the first time with trapped ions, and for the first time in the parameter regime where cooling to the motional ground state is possible. The measured cavity cooling dynamics are found to agree with a rate equation model without any free parameters. The third and final part of the thesis presents a theoretical proposal for interconversion between single trapped ion qubits and single photon qubits for quantum communication. The idea is to map the state of the single ion qubit to a superradiant collective state of several ions, which then couples strongly with single photons in an optical cavity.