Illinois Engineers Demonstrate 99% Fidelity in Modular Quantum System

Researchers at The Grainger College of Engineering, University of Illinois Urbana-Champaign, have demonstrated a high-performance modular architecture for superconducting quantum processors, published in Nature Electronics. The team connected two devices using superconducting coaxial cables to link qubits across modules, achieving approximately 99% SWAP gate fidelity, representing less than 1% loss. This modular approach, intended to overcome limitations of monolithic designs, facilitates scalability and reconfiguration, and is being further developed to connect more than two devices while retaining error detection and correction capabilities. The research builds upon existing modular designs and aims to create scalable, fault-tolerant, and reconfigurable quantum computing systems.

Modular Quantum Computing Emerges

The emergence of modularity represents a significant shift in the development of scalable quantum computers, mirroring the construction of complex systems from smaller, interconnected components. Researchers are increasingly focused on modular architectures as an alternative to constructing monolithic quantum computers, which face substantial challenges in assembling and controlling the millions of qubits required for practical computation. These modular designs involve creating and connecting smaller, high-quality modules, offering a potential pathway to overcome the limitations inherent in monolithic approaches.

Researchers at The Grainger College of Engineering at the University of Illinois Urbana-Champaign have demonstrated a high-performance modular architecture for superconducting quantum processors, building upon existing modular designs to facilitate the development of scalable, fault-tolerant, and reconfigurable quantum computing systems. Their work, published in Nature Electronics, addresses the constraints of monolithic superconducting quantum systems, which are limited in size and fidelity, directly impacting the success rate of logical operations; a fidelity of one represents a flawless operation, and achieving values approaching this benchmark is a key research objective. The team’s approach to modular quantum computing prioritises scalability, hardware upgrades, and tolerance to variability.

The team successfully connected two devices using superconducting coaxial cables to link qubits across modules, achieving approximately 99% SWAP gate fidelity, representing less than 1% loss. This ability to connect and reconfigure separate devices while maintaining high quality provides new insight into the design of communication protocols within quantum systems. While the potential of modularity has long been recognised, achieving the necessary performance levels to facilitate effective connection has proven challenging for researchers in the field.

Moving forward, the Grainger engineers will focus on scaling up the system, attempting to connect more than two devices while retaining the ability to detect and correct errors. This next phase of research will be critical in determining the viability of this modular approach for building practical, large-scale quantum computers, as the team seeks to validate the benefits of their design and assess its potential for future development. Wolfgang Pfaff, the senior author of the paper, highlights the need to rigorously test the system to determine whether it genuinely offers a viable path forward.

Overcoming Monolithic Limitations

Wolfgang Pfaff, an assistant professor of physics and the senior author of the paper, articulated the engineering challenges as determining whether a system can be assembled and manipulated to jointly operate on two qubits, achieving high quality and allowing for disassembly and reassembly. The ability to reconfigure the system post-assembly is crucial for identifying and correcting errors within the quantum processing system.

The team’s demonstration of approximately 99% SWAP gate fidelity – representing less than 1% loss – offers novel insight into the design of communication protocols within quantum systems. The field has long recognised the potential of modularity, with many groups converging on the idea of connecting larger units via cables, but achieving the necessary performance levels has proven challenging.

Moving forward, the Grainger engineers will focus on scaling up the system, attempting to connect more than two devices while retaining the ability to detect and correct errors. Pfaff stated the next phase of research will be critical in determining the viability of this modular approach for building practical, large-scale quantum computers, assessing whether it genuinely makes sense to proceed with the design.

Scaling and Future Prospects

Pfaff’s team successfully demonstrated a high level of performance by connecting two devices using superconducting coaxial cables to link qubits across modules, achieving approximately 99% SWAP gate fidelity – representing less than 1% loss. This ability to connect and reconfigure separate devices while maintaining high quality offers novel insight into the design of communication protocols within quantum systems. The field has long recognised the potential of modularity, with many groups converging on the idea of connecting larger units via cables, but achieving the necessary performance levels has proven challenging.

Moving forward, the Grainger engineers will focus on scaling up the system, attempting to connect more than two devices while retaining the ability to detect and correct errors. Pfaff stated the next phase of research will be critical in determining the viability of this modular approach for building practical, large-scale quantum computers, assessing whether it genuinely makes sense to proceed with the design.