Quantum advantage showdowns have no clear winners

Physicists at Toronto-based startup Xanadu published an experiment in Nature in which they created seemingly random numbers. They built a machine that included lasers, mirrors, and over a kilometer of optical fiber. There were over 200 beams of light bouncing around through the network. A series of detectors counted the number of light particles in each beam. The machine generated a total of 216 numbers at a time.

According to the Xanadu researchers, the laser-powered dice roll is beyond the capabilities of classical computing. A set of 216 numbers was generated in 36 microseconds. It would take Fugaku, the most powerful computer at the time, an average of 9000 years to produce a set of numbers from the same distribution.

The experiment is the latest in a series of demonstrations of so-called quantum advantage, where a quantum computer defeats a state-of-the-art supercomputer at a specified task. The experiment "pushes the boundaries of machines we can build," says physicist Nicolas Quesada, a member of the Xanadu team who now works at Polytechnique Montréal.

Laura Garca-lvarez was not involved in the experiment. A computation that is hard for classical computers has been done by this device. It doesn't mean commercial quantum computing.

What does Xanadu mean by quantum advantage? Caltech physicist John Preskill came up with the term "quantum supremacy" in 2011. It was called "quantum advantage" to avoid echoes of "white supremacy" since then. Xanadu thinks that "quantum advantage" means that the computer performed a useful task, which it did not.

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It was suggested by Preskill that achieving quantum advantage would be a turning point in the development of quantum computers. The first claim of a quantum computer beating a classical computer was leaked.

The meaning of the achievement is murkier as more researchers claim quantum advantage. There is still a race between quantum and classical computers. The beginning is what it is.

Several claims of quantum advantage have set off other researchers to develop faster classical methods to challenge them. The random-number-generating experiment that Xanadu's researchers performed was very similar to the one done by the researchers at GOOGLE. It would take 10,000 years for a state-of-the-art computer to create a collection of numbers, while it only took 200 seconds for a quantum computer. Researchers at IBM argued that a computer should only take 2.5 days to complete. A team using the Sunway TaihuLight supercomputer in China was able to complete the task in 304 seconds. The developers presented an even quicker method that year. Pan Zhang, a physicist from the Chinese Academy of Sciences, said that a larger computer would be able to execute this algorithm in a matter of seconds. The classical computer would be reinstalled.

"If you say you've gotten quantum advantage, you're saying that no one will ever simulation your experiment as accurately as your experiment was," says physicist Jacob bulmer of the University of Bristol. It's a big scientific moment when you say that. Strong evidence is required for large claims.

Researchers at the University of Science and Technology in China made a quantum advantage claim. The quantum computer was used by the team to generate numbers. The world's most powerful computer would take 2.5 billion years to create a set of numbers, according to their paper. The team showed that it would take 73 days to make a computer.