# Electromagnetic & Quantum

As quantum computers grow in size and complexity, it is increasingly difficult to rationally design quantum chips that are free of unwanted signals or distortions that can undermine device performance. Broadly speaking, “crosstalk” errors occur when qubit operations are unintentionally affected by electromagnetic (EM) wave interactions. These undesirable effects can occur at the macroscale (cm), where signals are disturbed by material interfaces in the housing circuit, or at the micro- or nanoscale when in-air EM leakage from the housing interacts with the qubits.

In an effort to aid in the design of quantum chips, Berkeley Lab researchers are developing a new simulation capability for higher-fidelity modeling of EM signals. We mainly tackle two aspects of this problem, with the goal of incorporating our efforts into a larger unified simulation framework. First, we note that the physical scales of the circuitry span several orders of magnitude. To address this multiscale aspect, we are developing a spatially adaptive, exascale-ready simulation tool for efficiently resolving the disparate length scales across the quantum device. Second, we note that Maxwell's equations are insufficient to model the entire device, in particular the superconducting qubits. To address this multiphysics aspect, we are developing new mathematical coupling strategies to seamlessly connect different models used to describe the relevant physics in various regions of the quantum circuitry. Altogether, we lay the foundation for unprecedented modeling capability that will position Berkeley Lab at the forefront of quantum chip design.

## Projects

### Accelerator Modeling with WarpX

WarpX is an accelerator modeling code for the exascale being developed as part of the Department of Energy’s Exascale Computing Program. Berkeley Lab researchers contribute to the core AMReX-based infrastructure for WarpX and the implementation of sophisticated mesh refinement algorithms. Our ongoing work includes extending WarpX to work efficiently on hybrid CPU/GPU platforms. **Contacts: Jean Luc Vay**

### ARTEMIS

ARTEMIS (Adaptive mesh Refinement Time-domain ElectrodynaMics Solver) is a time-domain electrodynamics solver that is fully open-source and portable from laptops to many-core/GPU exascale systems. **Contacts: Andy Nonaka, Jackie Zhi Yao **