Resilient multi-mode superconducting qubit design with evolutionary algorithms*

Multi-mode superconducting circuits offer a highly promising platform for engineering robust systems for quantum computation. Previous studies of single-mode devices have demonstrated that superconducting quantum systems can be engineered to be robust against various sources of noise and decoherence. Nevertheless, advancements in single-mode device design have revealed that no device with a single degree of freedom can be engineered to be simultaneously resilient to multiple sources of decoherence. This observation highlights the need to explore systems with a larger number of degrees of freedom, which have proven effective in providing protection against different error sources simultaneously. Unfortunately, this protection typically comes with construction constraints and limitations in manipulability.

In this study, we present novel multi-mode qubit architectures designed using evolutionary algorithms that exhibit desirable qubit characteristics, including restricted transitions, improved relaxation and dephasing times, and resilience against fabrication defects. This approach is valuable for identifying configurations that, although lacking the complete protection of symmetry-protected systems, strike a balance between manipulability, construction, and noise protection.