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The Zuchongzhi quantum computer, named after a 5th century mathematician, is capable of performing previously impossible tasks, according to its Chinese development team. Photo: Handout

China launches world’s fastest programmable quantum computers

  • Researchers say their supercomputer is 1 million times more powerful than its nearest competitor, Google’s Sycamore
  • A second light-based machine takes 1 millisecond to perform a task that would take a conventional computer 30 trillion years
Physicists in China say they have built two quantum computers with performance speeds which top their Western competitors – a superconducting machine and an even faster type which uses light photons to achieve never-before seen results.

According to the research team, the light-based Jiuzhang 2 can calculate in one millisecond a task that would take the world’s fastest conventional computer 30 trillion years.

News of the breakthroughs was given in an interview with the research team on state broadcaster CCTV which aired on Tuesday. The team’s findings are detailed in two papers published in the peer-reviewed academic journals Physical Review Letters and Science Bulletin.

Lead researcher Pan Jianwei said the Zuchongzhi 2 – a 66-qubit programmable superconducting quantum computer named after a 5th century mathematician – is 10 million times faster than the world’s fastest supercomputer and much more powerful than Google’s 55-qubit Sycamore, launched two years ago.
Chinese quantum physicist Pan Jianwei. Handout

The Zuchongzhi 2 was upgraded from an earlier machine released three months ago and can run a calculation task one million times more complex than Sycamore, he said.

Pan’s team also announced the Jiuzhang 2, another quantum computer based on light. It has a narrower field of applications but can reach a speed 100 sextillion (one followed by 23 zeroes) times faster than the largest conventional computers.

Despite their speed, these machines will not replace common computers any time soon. At this stage, they work only in a protected environment for short periods on highly specific tasks, and they make a lot of mistakes.

“In the next step we hope to achieve quantum error correction with four to five years of hard work,” said Pan, a professor with the University of Science and Technology of China in Hefei, in the southeastern province of Anhui.

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“Based on the technology of quantum error correction, we can explore the use of some dedicated quantum computers or quantum simulators to solve some of the most important scientific questions with practical value,” he added.

The Zuchongzhi machine’s circuits must be kept at an extremely low temperature for it to perform a complex task known as random walk, a model based on the movements of pieces on a chessboard. Applications range from predicting stock prices to calculating gene mutations, the formation of new materials, and air flows in hypersonic flight at Mach 5 or beyond.


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The model assumes that the movement of a chess piece can be completely random, without any association with previous moves. In classical computers the process is difficult to simulate because it requires a huge amount of calculation based on complex algorithms, but it becomes easy with the help of quantum physics.

The Zuchongzhi 2 machine can in theory calculate the random walks on 66 chess boards simultaneously – a mission impossible for any computer today.

Jiuzhang 2, named after an ancient mathematics text book, is an upgrade of a machine built by Pan’s team last year, uses photons, each one carrying a qubit – the basic unit of quantum information.

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“We have increased the number of photons from 76 to 113, (the new machine) is billions of billions of times faster than supercomputers,” said Lu Chaoyang, a lead scientist with the Jiuzhang project.

According to Lu, the Jiuzhang machine can perform a task known as boson sampling that simulates the behaviour of light particles when they pass through a maze of crystals and mirrors. It was initially proposed as a physical game without purpose but some recent studies suggest boson sampling could have some applications in cryptography.

A typical light-based computer is not programmable, but Jiuzhang 2 has a more flexible design that allows it to perform more than one calculation task, according to Pan’s team.


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These “two experimental quantum computers tackle the most complex problems yet”, said Barry C. Sanders, a professor with the Institute for Quantum Science and Technology at the University of Calgary in Canada.

Writing in a commentary published by Physical Review Letters, Sanders said their performance suggested “an end to the debate on whether quantum ‘primacy’ – the point at which a quantum computer outperforms the best possible classical computer – can be reached”.

China – which launched the world’s first quantum satellite in 2016 and the largest land-based quantum communications network in 2019 – has been a step or two behind the West in quantum computer technology.

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A recent adjustment in government strategy has seen increased investments in the computing sector and last month work started on the country’s first industrial estate dedicated to quantum computing technology in Hefei.

According to publicly available information, China’s military is using quantum technology for ultra-secure communication lines, radar that can detect stealth aircraft, and navigation devices for nuclear submarines.

But its application in civilian sectors remains limited. Some critics have said it could take years – if not decades – before quantum computers or communications generate a profit.

This article appeared in the South China Morning Post print edition as: Physicists make light work of quantum leap in faster supercomputers