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Google: We've achieved quantum supremacy! IBM: Nope. And stop using that word, please

Here's how to sim that with RAM and hard drive space

The esoteric world of quantum computing is all aquiver following a robust blog post from IBM essentially rubbishing claims from Google that it has achieved "quantum supremacy".

The post notes that quantum computing is approaching the limits of classical simulation and there are big questions as to how to evaluate and benchmark system performance. Quantum supremacy is the moment quantum machines begin to do things classical computers cannot.

But Big Blue dismissed Google's most recent claims for its 53-qubit processor, revealed first in a leaked document last month.

The Google-led group eventually published a paper, "Quantum supremacy using a programmable superconducting processor" in Nature on 23 October.

IBM noted this week: "In the preprint, it is argued that their device reached 'quantum supremacy' and that 'a state-of-the-art supercomputer would require approximately 10,000 years to perform the equivalent task'.

"We argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. This is in fact a conservative, worst-case estimate, and we expect that with additional refinements, the classical cost of the simulation can be further reduced."


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Big Blue does credit Google's team with "an excellent demonstration of the progress in superconducting-based quantum computing, showing state-of-the-art gate fidelities on a 53-qubit device, but it should not be viewed as proof that quantum computers are 'supreme' over classical computers."

IBM's researchers argue that the term "supremacy" is in danger of being misunderstood by those outside the rarefied world of quantum geeks.

The post acknowledges a recent article by Professor John Preskill which highlights two main objections: firstly, that the phrasing increases overhyped reporting of quantum computing and, secondly, that it evokes white supremacy.

IBM also suggested that quantum computers will likely work alongside and in concert with classical machines, rather than reign "supreme" over them – because both have their own strengths.

If you've had your morning coffee and are sitting in a comfy chair, the blog post details just how Google's experimental use of a 53-quibit chip to "implement an impressively large two-qubit gate quantum circuit of depth 20, with 430 two-qubit and 1,113 single-qubit gates, and with predicted total fidelity of 0.2 per cent" can in fact be simulated on a classical computer using both RAM and hard drive space.

So, not that supreme, then. ®

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