Google's Quantum Supremacy Challenged By Ordinary Computers, For Now

Google has been challenged by an algorithm that could solve a problem faster than its Sycamore quantum computer, which it used in 2019 to claim the first example of "quantum supremacy" -- the point at which a quantum computer can complete a task that would be impossible for ordinary computers. Google concedes that its 2019 record won't stand, but says that quantum computers will win out in the end. From a report: Sycamore achieved quantum supremacy in a task that involves verifying that a sample of numbers output by a quantum circuit have a truly random distribution, which it was able to complete in 3 minutes and 20 seconds. The Google team said that even the world's most powerful supercomputer at the time, IBM's Summit, would take 10,000 years to achieve the same result. Now, Pan Zhang at the Chinese Academy of Sciences in Beijing and his colleagues have created an improved algorithm for a non-quantum computer that can solve the random sampling problem much faster, challenging Google's claim that a quantum computer is the only practical way to do it. The researchers found that they could skip some of the calculations without affecting the final output, which dramatically reduces the computational requirements compared with the previous best algorithms. The researchers ran their algorithm on a cluster of 512 GPUs, completing the task in around 15 hours. While this is significantly longer than Sycamore, they say it shows that a classical computer approach remains practical.

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