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.

Jared B. Hertzberg, Eric J. Zhang, Sami Rosenblatt, Easwar Magesan, John A. Smolin, Jeng-Bang Yau, Vivekananda P. Adiga, Martin Sandberg, Markus Brink, Jerry M. Chow, Jason S. Orcutt