A quantum computer in China performed a calculation in seconds that would take the world's fastest classical supercomputer billions of years. The machine, called Jiuzhang 4.0, is the latest version of a photonic quantum computer developed by researchers at the University of Science and Technology of China in Hefei.
A speed gap wider than any before
The team ran a sampling problem known as Gaussian boson sampling. Jiuzhang 4.0 completed the task in a few seconds. The researchers estimated that the same problem would take a classical supercomputer about 2.4 billion years. That gap is far larger than what earlier versions of Jiuzhang achieved. The previous record holder, Jiuzhang 3.0, was about 10 quadrillion times faster than a classical machine. The new version is roughly 1 quadrillion times faster than its predecessor.
How the machine works and who built it
Jiuzhang 4.0 uses photons, or particles of light, to perform calculations. Unlike conventional computers that rely on silicon chips and electrical signals, this system sends photons through a network of mirrors, beam splitters, and other optical components. The photons interfere with each other in ways that encode the results of a computation. The machine was built by a team led by Pan Jianwei and Lu Chaoyang at the Chinese Academy of Sciences. The researchers published their findings in the journal Physical Review Letters in February 2025.
Why this matters locally and globally
For Chinese scientists and the broader research community, Jiuzhang 4.0 represents a concrete step toward what is called quantum supremacy, the point at which a quantum computer can outperform any classical computer on a practical task. The machine does not yet solve general problems, but it shows that photonic quantum computing can scale up. The team increased the number of detected photons from 255 in Jiuzhang 3.0 to 430 in Jiuzhang 4.0. That jump in scale made the speed leap possible. The achievement also keeps China in a tight race with the United States and other nations to build useful quantum computers.
The Jiuzhang 4.0 result does not mean quantum computers are ready for everyday use. The machine is still a specialized device built for one type of calculation. But the size of the speed gap shows how far photonic quantum computing has come. For researchers in Hefei and around the world, the question is no longer whether quantum computers can outperform classical ones. It is how soon they will do so on problems that matter.
