The field of quantum computing has long faced the challenge of building monolithic quantum computers, where scientists struggle to assemble and control large single units with millions of qubits. However, a modular approach offers a solution to this problem. Just as children's building blocks can be assembled into complex structures, scientists are exploring the creation of smaller, high-quality quantum modules that can be linked together into complete systems. Researchers from the Grainger College of Engineering at the University of Illinois Urbana-Champaign have demonstrated a modular architecture for superconducting quantum processors, paving the way for scalable quantum computing systems.

The research findings have been published in Nature Electronics, expanding on previous modular designs. Compared to monolithic superconducting quantum systems, the modular approach offers advantages in size and fidelity, where fidelity close to 1 means extremely low error rates. Modularity not only achieves system scalability but also improves hardware upgradability and tolerance to variability. Assistant Professor of Physics Wolfgang Pfaff stated: "We have created an engineering-friendly method to achieve modularity using superconducting qubits."

Pfaff's team connected two devices via superconducting coaxial cables, achieving cross-module qubit entanglement with SWAP gate fidelity up to approximately 99% and loss less than 1%. This result provides new insights for communication protocol design and demonstrates the enormous potential of modular quantum computing systems. Looking ahead, Grainger engineers will focus on scalability research, attempting to connect more than two devices while retaining error-checking capabilities. Pfaff said: "We're performing well now; we need to test if it can continue to scale and if it truly makes sense."