The scalability of superconducting quantum processors is hindered by frequency collisions among qubits, calling for precise and reliable frequency tuning techniques. Here, we develop a laser annealing platform and systematically investigate its effect on superconducting qubits. In contrast to previous reports that consistently observed an increase in the Josephson junction resistance Rn, we find that laser annealing can also reduce Rn by up to 24.9%, corresponding to a significant increase in qubit frequency with a tuning precision of 22.8 MHz. This complementary behavior enriches the phenomenology of laser annealing. Atomic-resolution scanning transmission electron microscopy and electron energy-loss spectroscopy analysis reveal a reduced Al coordination number and an increased oxygen vacancy concentration, which lower the effective barrier height and account for the decrease in Rn. Importantly, laser-annealed qubits maintain high coherence, and storage at −10 °C in high vacuum suppresses long-term resistance drift to below 0.5%. These results demonstrate that laser annealing provides a practical approach for stable and accurate frequency tuning. Beyond this, our findings suggest that the effect of laser annealing is richer than previously recognized and leave open the possibility of developing more versatile, potentially bidirectional frequency control for scalable superconducting quantum processors.
Recent advances in the alternating-bias-assisted annealing (ABAA) technique have successfully mitigated intrinsic Josephson-junction (JJ) fabrication variations. This new technique enables precision qubit frequency tuning alongside simplicity. However, it is critical to enhance tuning throughput and yield while investigating the factors that drive targeting performance as the technology scales. Here, we characterize ABAA tuning performance within a 150-mm wafer process flow and extend this technique to simultaneous, multi-channel tuning, demonstrating that a wafer-scale JJ resistance tuning precision of
σ=0.50±0.05% alongside a component-level yield of
≥98.8% can be achieved. Furthermore, we demonstrate a strong correlation between yield, tuning speed, and junction breakdown voltage, establishing the latter as a vital process control parameter for meeting production goals. Finally, we demonstrate a successful implementation of ABAA tuning on a quad-module quantum processor (Rigetti Cepheus-1-36Q), where we achieve an empirical frequency targeting precision of
σ∼30 MHz in both qubit and qubit-qubit detuning frequencies, contributing to high median two-qubit gate fidelities. These results confirm the efficacy and scalability of ABAA for high-precision Hamiltonian targeting, a critical enabler for modular superconducting quantum processor technology.
Fixed-frequency superconducting quantum processors are one of the most mature quantum computing architectures with high-coherence qubits and simple controls. However, high-fidelity multiqubit gates pose tight requirements on individual qubit frequencies in these processors, and these constraints are difficult to satisfy when constructing larger processors due to the large dispersion in the fabrication of Josephson junctions. In this paper, we propose a mixed-integer-programming-based optimization approach that determines qubit frequencies to maximize the fabrication yield of quantum processors. We study traditional qubit and qutrit (three-level) architectures with cross-resonance interaction processors. We compare these architectures to a differential ac-Stark shift based on entanglement gates and show that our approach greatly improves the fabrication yield and also increases the scalability of these devices. Our approach is general and can be adapted to problems where one must avoid specific frequency collisions.