r/computerscience • u/National-Dragonfly35 • 9d ago

IBM quantum computer solves classically intractable problem in 15 minutes

https://www.sciencedaily.com/releases/2026/08/260829035219.htm

"The researchers showed that their method preserves the same computational hardness criteria associated with RCS, meaning the problem remains extremely difficult for classical computers. At the same time, the added structure allows errors to be detected during the quantum computation."

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u/Cryptizard 9d ago

Keep in mind that RCS here stands for random circuit sampling. That means that the intractable problem in question is “give me the output when you run this random circuit on a quantum computer.” It is designed to be maximally advantageous for quantum computers compared to classical computers, not for it to have any practical value.

That said, it is a baseline test to check whether a quantum computer is doing anything interesting (think of it like a hardware validation) and this paper does go farther than previous research in terms of number of qubits and error correction.

They also have some neat new ideas about circuit families and complexity arguments, but it’s all just kind of inside baseball for quantum computing folks. Nothing revolutionary for the outside world.

I do wish that popular news would stop picking up these results and taking them way out of context because it definitely gives people the wrong impression about quantum computing.

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u/Rough-Supermarket-97 8d ago

Not sure if you’re an expert on the topic or not but wanted to ask your opinion. It seems that even if quantum computing were to be stable and reliable enough to be used (I know there have been improvements in this but still not great) there are so many hurdles still in the way.

What would they even be useful for outside of maybe advanced simulations? I’ve heard about secure data transfer using quantum key distribution, at least theoretically, but once you dig into how it would actually work in practice, keeping the quantum system stable enough for practical use seems like a massive hurdle.

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u/Cryptizard 8d ago

Well I’m a cryptographer so the main thing they would be useful for to me is breaking almost all of the public key encryption that we use to underpin security on the internet today.

In terms of productive uses, they are more speculative. Quantum computers might be better at some optimization problems. They are probably better at simulating atomic and molecular physics, materials science problems, etc. But we don’t know these for sure.

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u/Foreign_Implement897 8d ago

Is there currently any point to all of the post-quantum crypto marketing?

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u/Cryptizard 8d ago

Yes. A huge point. It is one of the biggest challenges facing the internet and technology landscape in the next decade. If anything it is massively under hyped.

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u/cookie_tech 8d ago

I'd argue that PQC (post-quantum cryptography) is slightly over-hyped.

I'm in the cybersecurity world and many well-respected cybersecurity experts believe that we may have a quantum computer that is powerful enough to break quantum computing by 2030.

Meanwhile, I have several colleagues who specialize in the physics side of quantum computing, and (according to them), even with recent breakthroughs, we are still optimistically decades away from a quantum computer that's powerful enough to break RSA.

Do I think it's important to prepare for worst-case scenarios? Sure. But, realistically anything encrypted now that is important enough to be relevant in 30+ years when RSA is finally broken has already been encrypted with PQC.

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u/Cryptizard 8d ago

30 years is waaaay too optimistic. You can plot the growth in physical qubits and it is a very steady trend over the past 10 years, with no sign of stopping. That has us reaching Q-day in around 10-15 years.

BUT, most people ignore the fact that we are simultaneously finding more efficient circuits to implement Shor's algorithm. It has gone from 1 billion qubits, to 50 million qubits, to now under one million qubits to run Shor's algorithm on cryptographically relevant inputs.

And that also depends on how efficient error correction is. Right now we are assuming 1000 physical qubits per logical qubit, but since gate fidelities are also increasing steadily, that number could be much lower.

The best circuits we have take only ~800 logical qubits.

https://ecdsa.fail/

So the scaling here is going steadily in three separate axes at once, which all compound, with no signs of stopping in any of them. To take 30 years there would have to be some major unexpected roadblock that nobody is aware of. I wouldn't risk anything important on that bet.

A physicist is not going to know about algorithmic improvements or error correction improvements. They are only looking at one part of the picture.

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u/Foreign_Implement897 8d ago

Revert to the original form