Optimized Weight-4 Superconducting Qubit Chip Design Workflow

Since the introduction of the transmon in 2007, many advances have been made in quality and scaling of superconducting qubits. This includes design tools such as Qiskit Metal and related codebases, as well as theoretical frameworks for modelling the transmon hamiltonian in a superconducting circuit and thus predicting physical properties of the resulting chip, such as coherence time, dispersive shift, transition frequency, charging energy, coupling strength, etc.



It is possible to combine these in a comprehensive workflow, detailing the process from the simplest qubit graph all the way to a physical layout for fabrication, and further describing an iterative feedback loop using empirical results to inform design choices and enable higher performance devices. Here we present the workflow as applied to a weight-4 floating transmon device, allowing the reader to understand and perform each step. We discuss the interplay of all relevant equations and constraints underway and provide experimental verification of the process, while demonstrating the potential of a data-driven feedback loop, as well as provide selected examples of programmatic automation to make processes more efficient and, importantly, more consistent. The workflow can easily be applied to qubit graphs that are larger or otherwise different from the weight-4 circuit.