Project lead\u00a0Professor Stephen Bartlett<\/a>\u00a0from the University of Sydney Nano Institute said quantum computers remain highly susceptible to \u2018noise\u2019, or external interference, and instability, making their scaling up to useful machines difficult to achieve.<\/p>\n \u201cQuantum computers will become even more useful if we can reliably detect and correct errors while calculations are taking place,\u201d said Professor Bartlett, Director of\u00a0Sydney Nano<\/a>. \u201cThis joint project with IBM helps us understand which parts of today\u2019s quantum hardware are introducing the most problems and where engineering improvements will have the greatest impact.\u201d<\/p>\n Quantum computers promise to solve certain classes of problems beyond the reach of conventional computers, including modelling complex chemical systems, designing new materials and pharmaceuticals or potentially improving optimisation problems. But their basic units of information \u2013 quantum bits or qubits \u2013 are extremely fragile and can lose information through even tiny disturbances introduced by their environments.<\/p>\n To address this, quantum computers use error-correction systems that repeatedly check qubits for mistakes during calculations. This means some of the physical qubits in the system are being used to find errors in the qubits doing the information processing. However, those checks themselves can introduce new errors.<\/p>\n MID-CIRCUIT MEASUREMENTS<\/p>\n To analyse where the errors emerged, the research team looked at the role of mid-circuit measurements. As a quantum system undergoes an operation, specific qubits are measured at intermediate stages of the operation. This measurement collapses those qubits to classical states, while allowing other qubits to maintain their coherence.<\/p>\n Measuring these states gives immediate feedback on how to manage the overall operation.<\/p>\n Professor Bartlett said: \u201cThis 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 \u2018idle\u2019 while the measurement is completed. This is a major stumbling block.<\/p>\n \u201cBut we can\u2019t get around this step \u2013 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. This is vital to design systems that can scale up and work.\u201d<\/p>\n USING AN IBM QUANTUM COMPUTER<\/p>\n Using a 156-qubit\u00a0IBM Quantum<\/a>\u00a0Heron r2 superconducting quantum processor, the researchers tested how well different error-correction methods preserved quantum information and enabled quantum logic operations.<\/p>\n Specifically, the team investigated how to reduce the \u2018idling\u2019 noise caused by the mid-circuit measurements.<\/p>\n By redesigning the error-correction circuitry to reduce the idling time, the researchers substantially improved performance. The revised approach increased logical qubit survival rates from below 90 percent to more than 96 percent for each error-correction cycle.<\/p>\n The researchers also found that measurement noise is one of the dominant limitations affecting the reliability of quantum logic operations on present-day devices.<\/p>\n Lead author\u00a0Dr Robin Harper<\/a>, from Sydney Nano and the\u00a0School of Physics<\/a>, said the research focused on understanding why error-corrected quantum operations fail.<\/p>\n \u201cQuantum error correction is essential for building large-scale quantum computers, but it introduces a very complex set of engineering challenges,\u201d Dr Harper said.<\/p>\n \u201cWe 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.<\/p>\n \u201cBy redesigning how those measurements are performed, we were able to significantly improve the reliability of the logical qubits.\u201d<\/p>\n The work is a direct outcome of the University of Sydney\u2019s collaboration with IBM,\u00a0announced in 2024<\/a>, to advance quantum error correction and benchmark different approaches to fault-tolerant quantum computing. That collaboration is funded by Intelligence Research Projects Activity (IARPA), a research funding agency of the US government.<\/p>\n It also builds on an international collaboration and\u00a0talent exchange program<\/a>\u00a0between the University of Sydney and University College London focused on next-generation quantum technologies. Co-author\u00a0Constance Lain\u00e9<\/a>\u00a0is a PhD student from UCL who was embedded in the Sydney Nano research group as part of the talent exchange.<\/p>\n Professor Bartlett said the collaboration demonstrated the importance of collaborations between universities and industry in advancing quantum technologies.<\/p>\n \u201cTesting these ideas on advanced quantum hardware allows us to better understand the practical challenges involved in scaling up quantum computing systems,\u201d he said.<\/p>\n \u201cThis kind of collaboration is essential if we want to develop quantum technologies that are useful outside the laboratory.\u201d<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2026\/06\/professor-stephen-bartlett-sydney-nano.-Credit-University-of-Sydney-1-1024x576.jpg\")
Professor Stephen Bartlett<\/a>, the University of Sydney Nano Institute<\/p>\n