Design and Analysis of Superconducting Qubits for Extensible Surface Coding*

We present the design and the finite-element electromagnetic analysis of superconducting qubits intended for an extensible surface-code architecture. Surface code, a promising architecture for fault-tolerant quantum computing, requires qubits with connectivity to all nearest neighbors. This interconnectivity, when combined with requirements for microwave and flux controllability, fast gating and readout, makes the design of superconducting qubits for surface coding challenging. We present the design, simulation, and experimental verification of several variants of seven-port high-coherence transmons.