Mitigation of frequency collisions in scalable superconducting quantum processors

Qubit frequency predictability is a challenge for scalable quantum processors, where cross-talk imposes hard limits on the frequency separation between qubits. Qubit frequency uncertainties arise from the fabrication process and are attributed to deviations in the Josephson junction area and tunnel barrier thickness. In this work, we demonstrate more than two-fold improvement in qubit frequency reproducibility, compared to our previous baseline, by making larger tunnel junctions and achieve ~40 MHz standard deviation in frequency. We further study the implications of this on qubit lifetime and frequency crowding on quantum processors based on the parametric-gate architecture. While qubits fabricated using the larger tunnel junctions maintained similar coherence to our baseline, the anticipated yield of collision-free chips on a quantum processor improves significantly.