An international research team including Professor Lee Seok-hyung of the Ulsan National Institute of Science and Technology (UNIST) has discovered a crucial mathematical solution enabling quantum computers and quantum technologies to operate in real-world conditions.
Professor Lee of UNIST's Department of Physics and a research team from Nanyang Technological University (NTU) in Singapore announced on the 4th that they have mathematically proven that most previously proposed quantum catalyst methods are difficult to reuse because catalysts gradually degrade even with minute noise. Only the "catalytic channel" method can maintain stable catalyst effects in actual environments.
A quantum catalyst is a quantum resource that enables otherwise impossible quantum state transformations. Like catalysts in chemical processes, it is called a quantum "catalyst" because it enhances efficiency by reusing existing quantum resources without being consumed itself.
According to the research, quantum catalysts theoretically assumed in previous studies gradually break down from even the slightest errors (noise) that occur when preparing input states for computation. This compromises reusability—the most important characteristic of a catalyst.
The research team proposed "catalytic channels" as a solution to avoid this problem. A catalytic channel is a quantum computation method designed so that the catalyst is always restored exactly to its original state, regardless of the input state. Existing quantum catalysts were designed under the ideal assumption that input states are perfectly prepared, making them vulnerable to minute noise.
The research team also clearly defined the limitations of catalytic channels. They presented an "impossibility theorem" showing that for representative quantum resources such as entanglement and coherence, it is fundamentally impossible to obtain new benefits even when applying the catalytic channel computation method. However, they demonstrated that under specific thermodynamic conditions, the effects of catalytic channels can be stably maintained even in the presence of noise.
Professor Lee explained, "This achievement is research that clarifies how far quantum catalysts can be maintained under realistic conditions where noise exists, rather than under ideal assumptions that are difficult to verify experimentally." He added, "The significance lies in providing guidelines for how to design noise-resistant structures in circuit optimization to enhance quantum computer computational efficiency and in quantum heat engine design."
A quantum heat engine is a device that shrinks classical heat engines like automobile engines or air conditioners to microscopic scales at the atomic or molecular level.
Professor Lee and Professor Nelly H. Y. Ng of NTU served as corresponding authors, while Dr. Son Jeong-rak of NTU participated as first author. Researchers from Aix-Marseille University in France and Nagoya University in Japan also contributed.
The research was supported by the National Research Foundation of Korea and the Institute for Information & Communications Technology Planning & Evaluation (IITP). The results were published on the 6th of last month in Physical Review Letters, a prestigious journal in physics.