Novel Gates with Superconducting Fluxonium Qubits

Abstract

Over the past two decades, superconducting qubits have emerged as a leading platform for gate-based quantum computation. Despite tremendous technological advancements, errors accumulating during gate operations are still a major bottleneck toward building a robust quantum computer. In general, these errors may be reduced by both increasing qubit coherences and improving gate design.

In this thesis, we develop the fluxonium qubit for superconducting quantum computing, a relatively newer qubit with advantages in qubit coherence. We first outline the design and simulation of these and other qubits, including a procedure to minimize flux noise in flux-tunable qubits. We then introduce a new fluxonium architecture containing fluxonium qubits coupled via a transmon coupler (FTF for fluxonium-transmon-fluxonium) and demonstrate high-fidelity novel gates, achieving up to 99.99% fidelity single-qubit gates and 99.9% two-qubit gates on the same device. We show that this coupling scheme has advantages for scalability, ZZ reduction, and performance. These results mark a technological milestone for fluxonium qubits and contribute to the ultimate goal of error-corrected universal quantum computing with superconducting qubits.