Probing Micromotion in a Multi-Segmented Blade-Style Ion Trap

Abstract

Trapped ions are a leading candidate in quantum computing platforms. Their all-to-all connectivity and high-fidelity multi-qubit interactions serve as an essential pillar for scaling up quantum computing. Trapping linear chains of 171Yb+ ions has applications ranging from digital quantum computation to analog quantum simulation of physically relevant models. Whilst these applications seem attractive, many experimental challenges prevent trapped ions from easily scaling up. The quadrupole multi-segmented blade-style trap is a leading trap architecture for quantum simulation because of its deep and quadratic confining potential, high optical access and capability to hold long chains of ions. Although, blade-style traps face challenges such as complex electronics control and ion heating caused by micromotion. Blade-style traps are traditionally hand assembled, and therefore are prone to misalignment, leading to increased levels of micromotion. This limitation causes many adverse effects, all negatively contributing to the quality of the quantum simulations performable with the blade-style trap. In this thesis, I will describe my work in building the electronic infrastructure to confine long chains of 171Yb+ ions in a multi-segmented blade-style trap. The bulk of my work will focus on probing micromotion in the trap by using a repump transition with a narrow enough linewidth. I will first present some background on ion dynamics, micromotion and fundamentals of ion trapping. Afterwards, I will discuss the multi-segmented blade-style trap used in this work, along with the electronics that I designed to drive the confining electromagnetic fields. A novel approach of using a balanced radio-frequency drive along with completely out-of-vacuum electronics allows us to reach high secular frequencies. Using this approach, we demonstrate long chains of up to 25 ions with qubit phase coherence exceeding 0.9 s, demonstrating good control over the magnetic field level. The rest of the thesis will present our approach to probe and minimize micromotion in the segmented blade-style trap. Here, I will demonstrate that our results show inherently low micromotion without any compensation fields, indicating that the assembly of the blades is quite optimal. Displacements below 1 μm are required radially to find the micromotion null. Additionally, I will demonstrate that there is low micromotion at the center and edge of a long chain of ions, showing that for large-scale quantum simulations, we can expect low axial and radial micromotion across a long chain of up to 25 ions. These results demonstrate that hand-assembled blade-style traps can exhibit inherently low excess micromotion, such that the inherent micromotion is at the limit of resolvability for the sideband spectroscopic method. This work will is crucial for obtaining low micromotion for when we eventually run large-scale quantum simulations in this trap.