Last month, physicists Published an interesting experiment at Toronto-based startup Xanadu nature They generate seemingly random numbers in it. During the pandemic, they built a tabletop machine called Borealis, consisting of lasers, mirrors and more than a kilometer of fiber optics. Inside Borealis, 216 beams of infrared light bounce through a complex network of prisms. A series of detectors then count the number of photons in each beam after passing through the prism. Ultimately, the machine generated 216 numbers at a time—one number corresponding to the photon count in each respective beam.
Borealis is a quantum computer, and according to the Xanadu researchers, this laser-driven dice roll is beyond the capabilities of classical or non-quantum computing. Borealis takes 36 microseconds to generate a set of 216 numbers from a complex statistical distribution. They estimated that Fugaku, the most powerful supercomputer at the time of the experiment, would take an average of 9,000 years to generate a set of numbers from the same distribution.
The experiment is the latest in a series of demonstrations of so-called quantum supremacy, in which quantum computers beat state-of-the-art supercomputers at specific tasks. Physicist Nicolas Quesada, a member of Xanadu’s team now at École Polytechnique, said the experiment “pushed the boundaries of what machines we could make.”
“This is a great technological advance,” said Laura García-Álvarez of Chalmers University of Technology in Sweden, who was not involved in the experiment. “The device performs computations that are considered difficult for classical computers. But this does not imply useful commercial quantum computing.”
So what exactly does Xanadu’s claimed quantum advantage mean? Caltech physicist John Preskill dubbed the concept “quantum supremacy” in 2011, describing it as “a quantum computer that can do things that classical computers can’t, whether those tasks are useful or not.” (From there Since then, many researchers in the field have turned to calling it “quantum supremacy” to avoid echoes of “white supremacy.” Xanadu’s paper actually calls it “quantum computing supremacy,” because they argue that “quantum supremacy” means the computer does a useful task – it doesn’t.)
Preskill’s words suggest that achieving quantum supremacy will be a turning point, marking the beginning of a new technological era in which physicists will begin designing useful tasks for quantum computers. In fact, expectations for the milestone were so high that Google researchers’ first claim in 2019 that a quantum computer was superior to a classical computer was leaked.
But as more and more researchers claim their machines have quantum advantages, the meaning of the achievement has become more obscure. On the one hand, quantum supremacy does not mean the race between quantum and classical computers is over. This is the beginning.
Every claim of quantum supremacy has prompted other researchers to develop faster classical algorithms to challenge the claim. In Google’s case, its researchers conducted an experiment similar to Xanadu’s random number generation. They wrote that a state-of-the-art supercomputer would take 10,000 years to generate a set of numbers, while their quantum computer would take just 200 seconds. A month later, IBM researchers argued that Google had used the wrong classical algorithm for the comparison and that a supercomputer should only take 2.5 days. In 2021, a team using the Sunway TaihuLight supercomputer in China showed that they could complete the task in 304 seconds — just a bit slower than Google’s quantum computer. A larger supercomputer can execute the algorithm in tens of seconds, said Pan Zhang, a physicist at the Chinese Academy of Sciences. That would put classic computers in the lead again.
