Researchers from the University of Sydney and IBM have quantified the sources of noise that limit the scaling of quantum computers, establishing a critical pathway toward more reliable quantum technology. Published in Nature Communications, the collaborative research identifies how errors emerge during quantum computations, focusing on the impact of essential checks for mistakes made during calculations. These measurements, while necessary for error correction, can introduce new errors due to the time required to complete them; the team investigated methods to reduce this “idling” noise. “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, explaining that the study pinpoints the performance levels needed for scalable systems. Using a 156-qubit IBM Quantum Heron r2 processor, the researchers demonstrated improved performance through redesigned error-correction circuitry.
Mid-Circuit Measurements Limit Quantum Error Correction
The collaborative team’s work, recently published in Nature Communications, quantifies how these essential checks for errors introduce new instabilities into quantum systems, impeding the development of reliable and scalable quantum technology. Professor Stephen Bartlett from the University of Sydney Nano Institute explained that quantum computers are inherently susceptible to noise, or external interference, and instability, making improvements to error correction vital. The core of the issue lies in the process of mid-circuit measurements, where qubits are assessed for errors during calculations. Professor Bartlett clarified, “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 utilized a 156-qubit IBM Quantum Heron r2 superconducting quantum processor to analyze the performance of different error-correction methods, specifically focusing on minimizing this idling noise.
By redesigning the error-correction circuitry to reduce the duration of these pauses, the researchers achieved a substantial improvement in qubit stability, increasing logical qubit survival rates from below 90 percent to more than 96 percent per error-correction cycle. Lead author Dr. Robin Harper, from Sydney Nano and the School of Physics, emphasized the focus on understanding why error-corrected quantum operations fail, stating, “We wanted to identify which physical processes were limiting performance on modern quantum devices.” The findings reveal that measurement noise itself is a dominant factor limiting the reliability of quantum logic operations on current devices, establishing a guide for future engineering efforts to improve quantum error correction and ultimately, build more powerful and dependable quantum computers.
Quantum computers will become even more useful if we can reliably detect and correct errors while calculations are taking place.
Published in Nature Communications, the findings detail how strategic improvements to mid-circuit measurement protocols can significantly boost the performance of quantum processors. This is a major stumbling block. However, the research revealed that by redesigning the error-correction circuitry to minimize this idle time, substantial gains in performance are achievable. Lead author Dr. “Quantum error correction is essential for building large-scale quantum computers, but it introduces a very complex set of engineering challenges,” Dr. 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 collaborative effort, detailed in Nature Communications, focused on the unavoidable performance limitations introduced by mid-circuit measurements, essential checks for errors that nonetheless disrupt the delicate quantum state. Their investigation specifically targeted the “idling” noise generated during these mid-circuit measurements, and the results demonstrated a pathway to substantial gains. Professor Bartlett emphasizes that this understanding is vital to design systems that can scale up and work, and highlights the importance of partnerships between academic institutions and industry leaders like IBM to translate research into tangible progress. The work builds on a 2024 collaboration between the University of Sydney and IBM, funded by the United States Intelligence Advance Research Projects Activity (IARPA), and underscores Australia’s growing role in the international quantum landscape.
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.
The team specifically focused on the unavoidable “idling” time inherent in mid-circuit measurements, where qubits must be temporarily paused while others are assessed, as lead author Dr. Harper said.
We found that measurement noise is one of the dominant limitations affecting the reliability of quantum logic operations on present-day devices.
See today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals.
