Optimizing frequency allocation for fixed-frequency superconducting quantum processors

Fixed-frequency superconducting quantum processors are one of the most mature quantum computing architectures with high-coherence qubits and low-complexity controls. However, high-fidelity multi-qubit gates pose tight requirements on individual qubit frequencies in these processors and their fabrication suffers from the large dispersion in the fabrication of Josephson junctions. It is inefficient to make a large number of processors because degeneracy in frequencies can degrade the processors‘ quality. In this article, we propose an optimization scheme based on mixed-integer programming 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.