Magnetic Flux and Nonlinear Dynamics of Classical and Quantum Superconducting Hardware

Abstract

Superconducting quantum computing is a promising path towards achieving fault-tolerant quantum computation. Control and readout of signals at mK temperatures and subsequent amplification to room temperature electronics has allowed for impressive feats such as the first demonstration of quantum supremacy / advantage. The scalability of current systems that enable quantum computation are hindered by signal latency, excess heat loads, and overcrowding of cables in the dilution refrigerator. In this thesis, we propose cryogenic solutions using magnetic flux that improve scalability of superconducting quantum processors. In an effort to bridge the energy gap between the mK and 4 K stages of the dilution refrigerator, we simulate a flux soliton amplifier that can provide up to 10x gain to flux soliton pulses with low-loss in a resistance free traveling-wave bias scheme. To address latency and spatial cable considerations, we simulate a flux soliton cryogenic pulse generator that uses breather oscillations to create microwave pulses in the range of 15 - 24 gigahertz with over 97% energy efficiency. In addition, we present an experimental investigation of transmission properties for resonantly phase-matched Josephson traveling-wave amplifiers in magnetic fields to develop useful intuition towards the challenge of operating cryogenic parametric amplifiers in high magnetic fields. Our work presents paths for utilizing magnetic flux as a resource to advance large-scale high-fidelity quantum computing.