Researchers grab Google’s ‘quantum supremacy’ using simple supercomputers – Meczyki.Net

Back in 2019, Google proudly announced that they had achieved what quantum computing researchers had sought for years: proof that esoteric technologies could outperform traditional ones. But this demonstration of “quantum supremacy” is being challenged by researchers who claim to have overtaken Google on relatively common supercomputers.

To be clear, no one is saying that Google lied or misrepresented its work—the painstaking and important research that led to the 2019 announcement of quantum supremacy is still extremely important. But if this new paper is correct, the classical versus quantum computing competition is still anyone’s game.

You can read the full story in the original article on how Google took quantum from theory to reality, but here’s a much shorter version. Quantum computers like the Sycamore are not yet superior to classical computers in anything, with the possible exception of one task: the simulation of a quantum computer.

It sounds like a cop-out, but the point of quantum supremacy is to show the method’s feasibility by finding a highly specialized and strange task that it can do better than even the fastest supercomputer. Because he gets a quantum foot in the door to expand that library of functions. Perhaps eventually all the work will be in quantum fast, but in 2019 for Google’s purposes, there was only one, and they showed in great detail the how and why.

Now, a team from the Chinese Academy of Sciences led by Pan Zhang has published a paper describing a new technique for simulating a quantum computer (specifically, some of the noise patterns it excludes) that are similar to classical ones. Takes a small fraction of the estimated time. Calculate to do so in 2019.

Not being a quantum computing expert nor a statistical physics professor, I can only give a general idea of ​​the Zhang et al technique. They put the problem in the form of a large 3D network of tensors, in which 53 qubits in a Sycamore, represented by a grid of nodes, are spaced out 20 times, representing 20 cycles in the process to simulate the Sycamore gates. The mathematical relationship between these tensors (each with its own set of correlated vectors) was then computed using a cluster of 512 GPUs.

An illustration from Zhang’s paper showing a visual representation of the 3D tensor array they used to simulate the quantum operation of Sycamore.

In Google’s original paper, it was estimated that it would take about 10,000 years to execute this scale of simulation on the most powerful supercomputer available at the time (Summit at Oak Ridge National Laboratory) – although to be clear, this is their estimate. That was 54 qubits were doing 25 cycles. 53 qubits to 20 is much less complex, but will still take on the order of a few years, as they estimate.

Zhang’s group claims to have completed it in 15 hours. And if they had access to a proper supercomputer like Summit, it could have been accomplished in a matter of seconds – faster than Sycamore. Their paper will be published in the journal Physical review paper; You can read it here (PDF),

These results have not yet been thoroughly tested and are yet to be replicated by people with knowledge of such things, but there is no reason to think that this is some kind of error or hoax. Google also acknowledged that the baton could be turned back and forth a few times before supremacy was established, as quantum computers are incredibly difficult to build and program, while the classical ones and their software are constantly being improved. (Its claims of introducing others to the quantum world were skeptical, but there are few direct competitors.)

University of Maryland as quantum scientist Dominic Hengleiter told the scienceThis is by no means a black eye for Google or a knockout punch for Quantum in general: “The Google experiment did what it had to do, start this race.”

Google may well strike with new claims of its own — it’s not standing still — and I’ve contacted the company for comment. But the fact that it’s also competitive is good news for everyone involved; It’s an exciting area of ​​computing and continues to do things like Google and Zhang raise the bar for everyone.