Effects of qubit frequency crowding on scalable quantum processors*

Lattices of transmon qubits offer a scalable architecture to build quantum processors. Long qubit coherence times and hardware-efficient cross-resonance gates enable low gate error rates. However, frequency-crowding among the qubits can increase gate errors. Neighboring qubits must have similar but non-degenerate excitation energies. In this talk we will quantify the effects of frequency crowding and consider how this behavior scales with device size for 50-qubit and larger systems. We will also discuss strategies to mitigate or eliminate frequency crowding during device fabrication.