Researchers at the University of California, Riverside have demonstrated a new approach to building larger and more reliable quantum computers by connecting multiple small chips into a single system. The study, published in Physical Review A, explores how “scalable” quantum architectures can be constructed using existing chip technology.
“Our work isn’t about inventing a new chip,” said Mohamed A. Shalby, the first author of the paper and a doctoral candidate in the UCR Department of Physics and Astronomy. “It’s about showing that the chips we already have can be connected to create something much larger and still work. That’s a foundational shift in how we build quantum systems.”
The research addresses two main challenges: scaling—handling greater amounts of data—and fault tolerance—the ability for a quantum system to detect and correct errors automatically. Shalby noted that linking separate chips has been problematic due to increased noise, especially when chips are housed in different cryogenic refrigerators.
“In practice, connecting multiple smaller chips has been difficult,” Shalby said. “Connections between separate chips — especially those housed in separate cryogenic refrigerators — are much noisier than operations within a single chip. This increased noise can overwhelm the system and prevent error correction from working properly.”
Despite these difficulties, simulations showed that even with links up to ten times noisier than individual chips, error detection and correction were still possible.
“This means we don’t have to wait for perfect hardware to scale quantum computers,” Shalby said. “We now know that as long as each chip is operating with high fidelity, the links between them can be ‘good enough’ — not perfect — and we can still build a fault-tolerant system.”
Shalby explained that reliable quantum computing requires logical qubits built from clusters of many physical qubits—a process essential for correcting natural errors in fragile quantum systems. The surface code is currently the most widely used technique for error correction; processors designed around this method manage errors within their own architecture.
The team conducted thousands of simulations across six modular designs under various conditions, drawing on parameters inspired by Google’s current quantum infrastructure.
“Until now, most quantum milestones focused on increasing the sheer number of qubits,” Shalby said. “But without fault tolerance, those qubits aren’t useful. Our work shows we can build systems that are both scalable and reliable — now, not years from now.”
The research was motivated by previous studies at MIT and supported by the National Science Foundation. Simulations were performed using tools developed by Google Quantum AI. Other contributors included Leonid P. Pryadko and Renyu Wang at UCR, along with Denis Sedov at the University of Stuttgart.
The paper is titled “Optimized noise-resilient surface code teleportation interfaces.”
