Prof. Roth has been named as one of the recipients of the Young Scientist Award at the 2023 Photonics & Electromagnetics Research Symposium! This conference will be held in Prague from July 3 - 6, 2023. Prof. Roth was selected for this award based on his paper that will be presented at the conference titled "Hybrid Maxwell-Schrödinger modeling of a fluxonium qubit capacitively coupled to a transmission line network".

Paper Abstract: Superconducting circuits are one of the leading architectures for building quantum information processing technologies. Although great progress has been made with these devices, significant engineering improvements are still needed to achieve practical quantum computation. One particular area for improvement is to increase the speed and fidelity of qubit state control and readout, which are accomplished with classical microwave pulses, without comprising the qubit coherence. One avenue to approach this is by using fluxonium qubits rather than the more popular transmon qubits. Fluxonium qubits benefit from having competitive coherence properties combined with a stronger nonlinearity that can, in principle, allow for faster high-fidelity operations than is achievable with transmon qubits. However, the increased nonlinearity also significantly complicates the theoretical analysis of fluxonium qubits, which correspondingly impacts the design of new state control and readout schemes. Hence, the use of general-purpose numerical methods is particularly attractive when designing quantum information processing devices with fluxonium qubits. However, despite the prevalent use of classical control pulses in these systems, the prevailing general-purpose numerical methods used to optimize these functionalities typically use inefficient fully-quantum methods or semiclassical approaches that do not self-consistently consider how the presence and state of the qubit modify the applied control and readout signals. In this work, we propose a self-consistent semiclassical Maxwell-Schrödinger method for numerically analyzing the control and readout of a fluxonium qubit that is capacitively coupled to a transmission line network. Our approach solves the fully-coupled dynamics of a classical transmission line wave equation and the time-dependent Schrödinger equation to describe the fluxonium state. By solving the system in this way, our method is significantly more robust and efficient than fully-quantum methods, while still being able to accurately characterize the control and readout effects of interest, which is not possible with existing semiclassical methods that are not self-consistent. We demonstrate this via a number of numerical examples, which we validate against relevant quantitative theoretical predictions.