China Unveils World's Fastest Quantum Computer

A prototype quantum computer named "Jiuzhang 4.0" has solved complex mathematical problems in less time than the blink of an eye. The same calculations would require the world's fastest supercomputer a period exceeding the entire age of the universe. Published Wednesday in the journal *Nature*, this achievement marks a new peak in quantum computational supremacy and strengthens China's leading position in the field.

Unlike traditional computers that process bits as either zero or one, quantum machines use quantum bits (qubits) that can exist in both states simultaneously. This superposition allows them to explore countless computational paths at the same time, offering a massive performance acceleration for tasks like solving specific mathematical problems or simulating quantum systems.

The "Jiuzhang" series belongs to the photonic path of quantum computing, encoding data in particles of light. Its performance depends on how precisely scientists can process and control those photons. A persistent obstacle has been photon loss; as optical networks expand, photons get lost in the maze, introducing errors that reduce computing power.

To overcome this, a team from the University of Science and Technology of China built a high-efficiency optical parametric oscillator light source and a hybrid spatially and temporally encoded interferometer. These innovations lay the foundation for a fault-tolerant photonic quantum processor. The researchers integrated 1,024 high-efficiency squeezed optical fields into a circuit containing 8,176 modes, achieving a source efficiency of 92% and a total system efficiency of 51%—significant advancements in low-loss photonic quantum information processing.

The hybrid spatially and temporally encoded architecture allows photons to interact across both space and time, enhancing network connectivity while keeping the physical device size manageable. Based on these improvements, the team was able to process and detect up to 3,050 photons, a huge leap from the 255 photons achieved with "Jiuzhang 3.0" in 2023.

Experiments showed that "Jiuzhang 4.0" generates the most complex data sample in just 25 microseconds. In contrast, "El Capitan," the world's most powerful supercomputer built by the United States, would need more than 10 to the power of 42 years to calculate the same result.

China achieved its first quantum computational supremacy in 2020 with the original "Jiuzhang" prototype, which used 76 photons, making the country the second in the world to reach this milestone and the first to do so in an optical system.

Quantum's Role in National Plans

Quantum technology is highlighted in China's 15th Five-Year Plan (2026-2030) as a future industry and strategic frontier requiring sustained strengthening. The plan calls for developing fundamental theories and foundational technologies while accelerating industrial applications, with goals set for developing world-class fault-tolerant quantum computers and scalable specialized quantum machines.