Engineering Cryogenic Trapped-Ion Systems for Stable Quantum States

Abstract

This dissertation presents the implementation and characterization of a cryogenic trapped-ion quantum computing platform developed as part of the Software-Tailored Architecture for Quantum Co-design (STAQ) project. The system utilizes $^{171}$Yb$^+$ ions confined in a microfabricated surface-electrode trap and manipulated using Raman and microwave-driven gates to realize high-fidelity quantum operations. Operating at cryogenic temperatures ($\approx4$K) within an ultra-high vacuum environment, the computer integrates advanced optical, mechanical, and electronic subsystems to achieve improved motional coherence and scalable ion control. A key focus of this work is the design of the system’s architecture—spanning trap packaging, laser beam delivery, RF drive circuitry, and cryostat layout—to support long-range programmable spin-spin interactions via Mølmer–Sørensen gates. Special emphasis is placed on the optimization of voltage delivery for improved motional mode stability, as well as the development of custom hardware and software tools for system automation. The thesis includes detailed studies of experimental protocols for entanglement generation and characterization. Algorithmic applications, including quantum simulations of spin models and ergodic protocols for frustrated ground state preparation are also explored. Numerical simulations complement the experimental work, providing insight into entanglement generation via engineered dissipation, and thermal state preparation. This work contributes a fully integrated experimental framework for trapped-ion quantum computing. It offers both a reproducible model and a testbed for future advances in quantum control and hybrid quantum-classical computation.