The December 2022 issue of IEEE Spectrum is here!

Close bar

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 twostudies in the journal Physical Review Letters.

The Conversation (2)
Godfree Roberts07 Nov, 2021
INDV

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 Jamali07 Nov, 2021
INDV

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

The Transistor at 75

The past, present, and future of the modern world’s most important invention

2 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan
LightGreen

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

Keep Reading ↓Show less