Researchers from the University of Sydney, working with IBM, have pinpointed factors limiting quantum computer performance and demonstrated pathways to overcome them, findings now published in Nature Communications. The team’s work improves understanding of how errors emerge during quantum computations, a crucial step toward building more reliable quantum technology. Analyzing the role of mid-circuit measurements, repeated checks for qubit errors during calculations, the researchers discovered ways to reduce performance bottlenecks caused by necessary “idling” time. “Quantum computers will become more useful if we can reliably detect and correct errors while calculations are taking place,” said Professor Stephen Bartlett, Director of Sydney Nano. Using a 156-qubit IBM Quantum Heron r2 processor, the collaboration quantified the performance needed from these error checks to enable scalable quantum systems.
Mid-Circuit Measurements Limit Quantum Computation Speed
The team’s findings, published in Nature Communications, pinpoint how these interruptions to maintain qubit coherence introduce new challenges to scaling up quantum technology. Quantum computers are inherently susceptible to noise and instability, making their advancement to practical machines exceptionally difficult; however, the research offers a pathway to mitigate these issues. Their investigation focused on minimizing the idling noise created when qubits are measured mid-operation, a pause where all other processes must temporarily halt. This interruption, repeated numerous times during each step of a quantum computation, presents a major obstacle to faster processing. By redesigning the error-correction circuitry to reduce this idling time, the researchers achieved a substantial improvement, increasing logical qubit survival rates from below 90 percent to more than 96 percent for each error-correction cycle.
Lead author Dr. Robin Harper, from Sydney Nano and the School of Physics, clarified that the research aimed to understand why error-corrected quantum operations fail. “What we found is that the act of measuring qubits during a calculation can itself create instability,” Dr. Harper said, adding that by altering how these measurements are performed, they significantly enhanced the reliability of the logical qubits. The work underscores the importance of collaboration between academic institutions and industry leaders like IBM in tackling the complex engineering challenges of building large-scale, functional quantum computers.
We wanted to identify which physical processes were limiting performance on modern quantum devices. What we found is that the act of measuring qubits during a calculation can itself create instability.
IBM Heron r2 Processor Validates Error-Correction Improvements
Researchers are steadily refining techniques to combat the inherent instability of qubits, and recent work leveraging IBM’s hardware demonstrates tangible progress in error mitigation. A collaboration between the University of Sydney and IBM has yielded detailed insights into the sources of error during quantum computations, specifically pinpointing the impact of mid-circuit measurements on qubit coherence. The investigation utilized a 156-qubit IBM Quantum Heron r2 superconducting quantum processor to analyze the performance of different error-correction methods. Lead author Dr. Robin Harper said, “Testing these ideas on advanced quantum hardware allows us to better understand the practical challenges involved in scaling up quantum computing systems.” The team’s work is a direct outcome of a University of Sydney and IBM collaboration, funded by the Intelligence Research Projects Activity (IARPA), and designed to benchmark approaches to fault-tolerant quantum computing.
This occurs many, many times during each step of the quantum computation. Each such mid-circuit measurement takes time and everything else in the operation has to ‘idle’ while the measurement is completed. This is a major stumbling block.
The team’s work, detailed in Nature Communications, focused on minimizing disruptions caused when qubits are checked for errors during complex calculations, a process essential for scaling quantum computing power. Specifically, the researchers targeted the idling noise created as qubits pause while measurements are completed, a previously significant impediment to performance. Lead author Dr. Robin Harper said the research focused on understanding why error-corrected quantum operations fail.
University of Sydney & IBM Advance Error Correction Research
Their work, detailed in Nature Communications, doesn’t simply improve understanding of error emergence, but quantifies the performance limitations of mid-circuit measurements, the repeated checks for errors essential to maintaining quantum information. This detailed analysis allows for targeted engineering improvements, a crucial step toward scalable quantum systems. Professor Stephen Bartlett, from the University of Sydney Nano Institute, explains that current quantum computers are highly susceptible to external interference and instability, hindering their development. The team focused on minimizing the disruption caused when qubits are measured during calculations, a process that forces them into classical states while other qubits attempt to maintain their delicate quantum coherence. Each measurement necessitates a period of idling for the entire system, creating a significant performance drag. “But we can’t get around this step – it is an essential element of quantum error correction. What we have done in this study is pin down quantitatively what kind of performance we need out of these error checks,” Bartlett said. Lead author Dr. Robin Harper said…
Quantum computers will become even more useful if we can reliably detect and correct errors while calculations are taking place.
