TOKYO -- It is called "quantum supremacy," the ability to harness quantum technology to achieve computational power that cannot be achieved by a conventional computer. So far, only Google has laid claim to reaching that milestone, but now a team of researchers in China say they too conquered that level.
So far, the quantum computers used are designed to solve specific, narrowly defined problems, so the long-term outlook for the technology is still uncertain, but China's growing prominence in the field is striking.
In an article published in the Dec. 3 issue of the American academic journal Science, the Chinese team, including researchers from the University of Science and Technology of China, said they were able to solve a problem in 200 seconds that would have taken Japan's Fugaku conventional supercomputer, currently the world's fastest, 600 million years or 2.5 billion years by China's Sunway TaihuLight supercomputer.
Using particles of light known in physics as photons, the team built a quantum computer to solve a specific problem called "Gaussian boson sampling," which involves calculating the distribution of a large number of photons.
It is difficult for conventional computers to calculate a problem that involves the strange quantum properties of photons. But quantum computers are based on quantum mechanics and promise to bring innovative changes to the development of materials and drugs, assessment of financial risks and artificial intelligence using big data. But they were regarded as a "dream technology" due to the difficulty of development.
That changed when Google claimed the achievement of quantum supremacy in the British scientific journal Nature last year.
Google said in that report that it took 200 seconds to perform a calculation that would have taken a supercomputer 10,000 years to compute.
Google checked the output from a random-number generator for that achievement, but since then the focus has shifted to possible practical applications for the real world.
Google performed the calculation in superconducting electronic circuits where temperatures are reduced so low that material is in a superconducting state. With IBM adopting the same approach, superconducting quantum computing has become the mainstream of the technology.
In contrast, the Chinese team employs photons traveling through circuits that combines mirrors and other materials. Because it does not require equipment to deep refrigeration and vacuum vessels, it is much easier to use.
"The Chinese technology will undoubtedly contribute to the development of optical quantum computing," said Shuntaro Takeda, associate professor at the University of Tokyo.
But Google's quantum computer is "overwhelmingly superior" to China's at present, Takeda said, noting that the Chinese computer is aimed specifically at achieving quantum supremacy and is not considered applicable to other calculations. Therefore, there is no current prospect for the practical use of the Chinese technology, and it is unclear how it can be improved.
Nevertheless, there is no denying that China is making progress in quantum computing technology.
Pan Jianwei, of University of Science and Technology of China and who is known as "Father of Quantum" in China, led the latest breakthrough. Credited for respected achievements in studies on quantum communication, cryptography and other technologies, he is globally known as well.
The Chinese experiments suggest the team is well funded and has many excellent researchers, said Tomoyuki Horikiri, associate professor at Yokohama National University.
And the cutting-edge devices used in the project indicates that China has also stepped up its fabrication abilities, Horikiri said.
China has positioned the development of quantum computers as a key project, setting up related facilities in Anhui Province at a cost close to almost $10 billion. It is expected to keep accelerating the development program.
The U.S. government has a plan to invest $1.3 billion over five years from 2019 to develop quantum computing technologies. Competition in the field between the U.S. and China is expected to further intensify even after the change of government in the U.S. in January.
