Two of World’s Biggest Quantum Computers Made in China

Quantum computers Zuchongzi and Jiuzhang 2.0 may both display "quantum primacy" over classical computers

2 min read
A large amount of equipment and wires mounted on a peg board and resembling a maze.

Chinese optical quantum computer Jiuzhang 2.0 can solve a problem 10^24 faster than a classical computer.

Chao-Yang Lu/University of Science and Technology of China

Two of the most powerful quantum computers in the world to date now both come from China, and new experiments with them re-ignite the controversy over what kinds of problems might be quantum computationally solvable that couldn't begin to be solved by a conventional supercomputer.

A quantum computer with great enough complexity—for instance, enough components known as quantum bits or “qubits"—could in theory achieve a "quantum advantage" allowing it to find the answers to problems no classical computer could ever solve. In principle, a quantum computer with 300 qubits could perform more calculations in an instant than there are atoms in the visible universe.

In 2019, Google argued it displayed such "quantum primacy" with its 53-qubit Sycamore processor, carrying out a calculation in 200 seconds that the company estimated would take Summit, the world's most powerful supercomputer at that time, 10,000 years. However, IBM researchers later called that quantum advantage claim in question, arguing that with better classical algorithms, Summit could actually solve that problem in 2.5 days.

“The current state of the art is that no experiments have demonstrated quantum advantage for practical tasks yet."
—Chao-Yang Lu, The University of Science and Technology of China

Now scientists in China have tested two different quantum computers on what they say are more challenging tasks than Sycamore faced and showed faster results. They note their work points to "an unambiguous quantum computational advantage."

In one study, the researchers experimented with Zuchongzi, which used 56 superconducting qubits on a task whose solutions are random instances, or samples, from a given spread of probabilities. They found Zuchongzi completed such a sampling task in 1.2 hours, one they estimated would take Summit at least 8.2 years to finish. They also noted this sampling task was tens to hundreds of times more computationally demanding than what Google used to establish quantum advantage with Sycamore.

In another study, the scientists tested Jiuzhang 2.0, a photonic quantum computer, using Gaussian boson sampling, a task where the machine analyzes random patches of data. Using 113 detected photons, they estimated Jiuzhang 2.0 could solve the problem roughly 1024 faster than classical supercomputers.

Although the sampling task used in experiments with Zuchongzi has no known practical value, the Gaussian boson sampling problem on which Jiuzhang 2.0 was tested potentially has many practical applications, such as identifying which pairs of molecules are the best fits for each other. As such, this work may have quantum chemistry applications in simulating vital molecules and chemical reactions, says physicist Chao-Yang Lu at the University of Science and Technology of China in Hefei, a co-author on both studies.

These new experiments are "solid and necessary steps toward building increasingly advanced quantum computers," Lu notes. But he also cautions against the increasing hype surrounding quantum computing.

"So far, the computational problems that can truly benefit from quantum computing are still quite limited," Lu says. "The current state of the art is that no experiments have demonstrated quantum advantage for practical tasks yet. While we should not be too pessimistic and short-sighted as 'the world needs only five quantum computers,' we should also make a difference between optimism and exaggeration."

The scientists detailed their findings Oct. 25 in two studies in the journal Physical Review Letters.

The Conversation (2)
Godfree Roberts 07 Nov, 2021

Apparently, China has also earned line honors for conventional computing, with two machines recording sustained 1.3 exascale speeds.

Both machines are upgrades of previous computers, with faster scratch-built, machines expected in 2022.

Shah Jamali 07 Nov, 2021

Wow that's amazing. It is like a shell or orbit, love to read about technically and Quantum shell computers ❤️

The Lies that Powered the Invention of Pong

A fake contract masked a design exercise–and started an industry

4 min read
Pong arcade game in yellow cabinet containing black and white TV display, two knobs are labeled Player 1 and Player 2, Atari logo visible.
Roger Garfield/Alamy

In 1971 video games were played in computer science laboratories when the professors were not looking—and in very few other places. In 1973 millions of people in the United States and millions of others around the world had seen at least one video game in action. That game was Pong.

Two electrical engineers were responsible for putting this game in the hands of the public—Nolan Bushnell and Allan Alcorn, both of whom, with Ted Dabney, started Atari Inc. in Sunnyvale, Calif. Mr. Bushnell told Mr. Alcorn that Atari had a contract from General Electric Co. to design a consumer product. Mr. Bushnell suggested a Ping-Pong game with a ball, two paddles, and a score, that could be played on a television.

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