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

Area of Science:

• Quantum Computing
• Cryogenic Engineering
• Materials Science

Background:

• Scaling superconducting quantum processors to hundreds of qubits is critical for achieving quantum advantage and implementing robust quantum error correction.
• Integrating extensive control and readout wiring into cryogenic systems presents significant thermal management and performance challenges.

Purpose of the Study:

• To develop and validate a high-density wiring solution for large-scale superconducting quantum processors.
• To address the thermal budget constraints within dilution refrigerators for qubit control and readout.

Main Methods:

• Systematic analysis of the thermal budget in a dilution refrigerator.
• Development of high-density 0.5 mm SCuNi-CuNi coaxial cable sets optimized for heat load management.
• Integration of 696 control lines and 40 readout amplification chains.

Main Results:

• Successful operation of 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.
• Demonstrated performance with a 540-qubit processor (average T1 of 35 μs) and a 156-qubit processor (182 tunable couplers).
• Achieved high average fidelities: 99.9% for single-qubit gates and 99.0% for two-qubit gates.

Conclusions:

• A viable high-density wiring solution for controlling and measuring processors at the 500-qubit scale has been demonstrated.
• The developed coaxial cable sets effectively manage heat loads, enabling stable cryogenic operation.
• This work provides critical engineering insights for the development of larger-scale quantum computing systems.