High-density wiring solution for 500-qubit scale superconducting quantum processors

Scaling superconducting quantum processors to hundreds of qubits is essential for demonstrating quantum advantage and implementing quantum error correction codes with larger distances. A key challenge is integrating control and readout wiring without compromising cryogenic or electronic performance. To address this, we performed a systematic analysis of the thermal budget within a dilution refrigerator and developed high-density 0.5 mm SCuNi-CuNi coaxial cable sets optimized for heat load management. This enables the integration of 696 control lines and 40 readout amplification chains into a dilution refrigerator with a cooling power of 1 mW at 100 mK, maintaining a stable base temperature of ∼8 mK for over a year. We validated the platform's performance with two large-scale quantum processors: a 540-qubit processor with an average T1 of 35 μs and a 156-qubit processor with 182 tunable couplers, achieving average fidelities of 99.9% for single-qubit gates and 99.0% for two-qubit gates. This study demonstrates a viable high-density wiring solution for controlling and measuring processors at the 500-qubit scale and provides critical engineering insights for larger-scale quantum computing systems.