Efficiently Building and Characterizing Electromagnetic Models of Multi-Qubit Superconducting Circuits

TL;DR

This paper presents a novel electromagnetic modeling and characterization approach for multi-qubit superconducting circuits, enabling efficient Hamiltonian construction and parameter estimation to improve scalability and performance.

Contribution

It introduces a combined vector fitting and impedance interconnection method for modeling complex multi-qubit circuits with electromagnetic simulations.

Findings

Efficient Hamiltonian construction for multi-qubit circuits.

Accurate estimation of qubit coupling and relaxation parameters.

Applicable to circuits with lumped and distributed components.

Abstract

In an attempt to better leverage superconducting quantum computers, scaling efforts have become the central concern. These efforts have been further exacerbated by the increased complexity of these circuits. The added complexity can introduce parasitic couplings and resonances, which may hinder the overall performance and scalability of these devices. We explore a method of modeling and characterization based on multiport impedance functions that correspond to multi-qubit circuits. By combining vector fitting techniques with a novel method for interconnecting rational impedance functions, we are able to efficiently construct Hamiltonians for multi-qubit circuits using electromagnetic simulations. Our methods can also be applied to circuits that contain both lumped and distributed element components. The constructed Hamiltonians account for all the interactions within a circuit that are described by the impedance function. We then present characterization methods that allow us to estimate effective qubit coupling rates, state-dependent dispersive shifts of resonant modes, and qubit relaxation times.