Laser-annealing Josephson junctions for yielding scaled-up superconducting quantum processors

As superconducting quantum circuits scale to larger sizes, frequency crowding becomes a formidable challenge. This work presents a solution for fixed-frequency transmon architectures by systematically adjusting qubit frequencies post-fabrication via laser annealing of Josephson junctions. The method achieves nearly a tenfold improvement in the precision of setting qubit frequencies. The authors identify and model types of frequency “collisions” that impair transmon qubits and cross-resonance (CR) gates, computing the probability of avoiding all such conditions as a function of frequency precision. Without post-fabrication tuning, the probability of finding a workable lattice approaches zero as systems scale. With demonstrated precisions, collision-free lattices can be found with favorable yield. These techniques and models are employed in available systems and will be indispensable as systems scale to larger sizes.