Design and Analysis of Multi-Qubit Superconducting Chips for Extensible Surface Coding*

We present an effective numerical method to analyze qubit-qubit avoided crossings and two-qubit gate times in a superconducting multi-qubit chip. Our hybrid simulation approach, combining finite element and circuit simulation, is a convenient tool to investigate complex chip layouts with limited computational resources. The simulation method has been applied to design and investigate a new multi-qubit chip layout. This new chip design and improved fabrication process have allowed us to also reduce mode hybridization between qubits and resonators and to increase qubit coherence time.