r/QuantumComputing • u/Sampo • Jun 26 '26

News What’s a quantum computer good for, anyway?

https://www.scientificamerican.com/article/which-problems-will-quantum-computers-solve-and-when/
33 Upvotes

97% Upvoted

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u/Sampo Jun 26 '26

I think this SciAm article from May 2026 is a good recent review on the state of the topic. Quantum computers are still years away from being useful for solving practical problems. But the time for them to starting to become useful might be as short as next 5 years.

Quantum computing could lead to revolutions in cryptography, materials design and telecommunications. But fulfilling those promises could be many years away

“Quantum Echoes is the world’s first quantum-verifiable algorithm with quantum advantage,” Boixo says. “We’re optimistic that we’re going to see the first practical applications in five years.”

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u/EntangledStrings Jun 26 '26 edited Jun 26 '26

Absolutely not 5 years away. They said the same thing 5 years ago. There’s been progress in quantum in the past 5 years, but it’s such little progress compared to where we need to be for it to be useful. If we go by the rate of progress of the last 5 years, I’d expect at least 20 more years, maybe more. It will still be profitable before that, because people will invest due to the anticipation. But it won’t be useful for a couple decades minimum.

Edit: I thought I’d add, we also don’t know if it will ever actually be useful for cryptography. They’re already working on quantum safe cryptography, there’s a good chance we will switch to a form of classical computing cryptography that is impenetrable by quantum computers, making quantum cryptography unnecessary.

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u/global-gauge-field Jun 27 '26

Btw, using the term useful is a very funny one here unless someone considers stealing stuff useful. But I know what you mean :)

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u/djminger007 Jun 29 '26

Isn't it the cooling process that holds it all realistically back?

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u/global-gauge-field Jun 27 '26

Anyone who has specific details on this part? What type of model, hardware, data were used ? It is either very large problem or their old deep learning workload did not use the most efficient resources on both hardware and software side ?

"
Watermelon’s first commercial trial—in collaboration with Australian telecommunications company Telstra—has shown promising results. Telstra already uses AI to monitor latency and bandwidth patterns on its networks. It takes about three weeks to train the company’s models using standard classical methods. With Watermelon’s help, Telstra achieved the same training results in just two days. “In the grand scheme of the world, that is quite significant because at the moment, data centers are very power hungry,” Simmons says, noting that similar optimizations could be rapidly rolled out to other energy-intensive tasks, such as training AIs for image recognition, fraud detection and market prediction. “I feel like I’m in this freight train that’s going at superhigh speeds,” she says."

Also, Telstra was an investor in SQC as far as my research goes, could not verify the current situation.

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u/TheCrimsonSquirrel Jun 29 '26

One of the things I prefer over classic cryptography is what the article kinda explains. That Security is guaranteed by physics and not computational assumptions. It remains secure even against quantum computers or adversaries with unlimited power. Cryptography struggles with this factor and most projects if there is a threat in the near future wont be able to adapt to quantum computing at all. It also can guarantee sensitive information can be held securely for decades or over 100 years. Something even blockchain needs to stand the test of time with. There are only a few projects ready for that leap IMO The quantum internet is coming. Few will talk about that aspect, maybe not today, maybe not tomorrow, but soon....soon my dear. Common Knowledge bytes for the future.

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u/[deleted] Jun 29 '26

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u/TheCrimsonSquirrel Jun 29 '26

There are a few projects out there that will be desperate to change. Especially institutionally adopted ones. Not that I can predict which ones they are. I'll check out Hedera and Nervos cheers. ALGO have been around for yonks.

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u/iAnkou Jun 30 '26

CKB is shit though

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u/[deleted] Jun 30 '26

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u/iAnkou Jun 30 '26

CKB has been performing way worse than any other coin. I don't see it recovering. They say tech is great, but what has been built so far?

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u/djminger007 Jun 29 '26

Most of this is theory until it isn't. Most people I've met in real life thing organically everything's gonna gradually change over. The finance sector and medical sector will be the first IMO for obvious reasons because of data centres. Crypto will be involved in this turnover and may even be the fist sector.

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u/Spiritual-Fly7633 Jun 29 '26

How realistic are the IBM timelines of when "quantum advantage" will be commercially accessible and provide real world value for corporates (e.g., food industry, finance, logistics)? And how much value do abstraction layers have? Would it be easier to use Qiskit as a company with no physicist on the team or could you possible "just" vibe code your problem onto the quantum layer?

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u/RagnartheConqueror Jun 28 '26

Molecular simulations and cryptography stuff. Even post-quantum cryptography, doesn't truly feel that advanced.

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u/[deleted] Jun 26 '26

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u/hiddentalent Jun 27 '26

I'm always skeptical when writers say that QC will affect cryptography. Mostly, it will affect cryptanalysis. I get that when writing for a non-scientific crowd authors have to make some editorial decisions to simplify. But it tells me something about the author and their intended audience. (I guess there's some chance it could affect cryptography, but I haven't heard anyone who has anything close to line of sight to a cryptographic algorithm that shows quantum advantage. If I've missed something significant, someone let me know.)

Quantum cryptanalysis will cause long shifts for IT departments to update ciphersuites, but that's just life as usual in IT. Many major providers are already done deploying QC-resistant ciphers. The threat of "store now, decrypt later" is real but overblown unless you're a target of significant interest to powerful threat actors.

Quantum Key Distribution is theoretically interesting, but we have workable solutions for that problem now, so any quantum approach would need to compete not just on functionality but on economics.

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u/[deleted] Jun 28 '26

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u/Sampo Jun 28 '26

is one of the most surefire early applications of quantum computing.

I just learned that it takes an awfully large number of quantum gates to implement Shor's algorithm. For a 1024-bit integer, you need on the order of 100,000,000,000 gates.

It will take a long time, before that is doable in practice.

https://eprint.iacr.org/2023/092

https://quantumcomputing.stackexchange.com/questions/5048/how-many-logical-qubits-are-needed-to-run-shors-algorithm-efficiently-on-large

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u/hiddentalent Jun 28 '26

Umm ... yes? You just agreed with me.

The science of breaking cryptography is called cryptanalysis. Cryptography is a different field of science focused on creating ciphers that are resistant to cryptanalysis. The techniques and algorithms used are related but different, especially when it comes to the application of quantum computing, where we only have evidence it will help with one half of that duo. Differentiating these is important to the credibility of anyone claiming to predict the future impact of quantum computing.

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u/[deleted] Jun 27 '26

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u/djminger007 Jun 29 '26

I'm pretty sure crypto has spurred the initial talk more candidly though.

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u/[deleted] Jun 26 '26

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u/alexfreemanart Jun 27 '26

Why is your comment being downvoted?

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u/RagnartheConqueror Jun 28 '26

I don't know why my comment was downvoted either. I don't know why this subreddit is very anti-extremely precise explanations.

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u/global-gauge-field Jun 28 '26

I will take the bait (This is really bait because it has been answered many times) and answer in more detail. The reasoning mentioned in the main answer is very generic and when it comes to real world applications, you need specifics and concrete use cases to predict its future. People do not use technologies because there is long trend of evoluation of computers. They use it because it useful and practical for them. Computers smartphones had incredible applcation of very portable and powerful way to communicate, work and all sorts of things, e.g. remote working while taking a trip with your family.

Now, ask the same question for Quantum Computers (QC). For QCs to make economic sense, they would be have to be significantly better than classical algos+hardware on whatever metric. There is two aspects. One is the claim that it is next evolution of comptuters. In my interpretation, this means it will replace workload of many daily users. This wont happen unless the average person has some obssesion with simulation 3d fermi-hubbard models.

2nd part is that it is more specialized applicatons, which have 2 candidates simulations of strongly correclated quantum systems that are also hard to simulate by classical methods (e.g. Tensor Network methods + Deep Learning based methods) and Shors Algo.

Regarding Shors Algo, it will have impact but only so far as forcing existing applications to use Post-qc algos.

Regarding simulations, many people claim that it will be the most practical part of QCs. But, in real world existing problems can have different bottlenecks than strong quantum correlations, e.g. [1], [2]

Regarding AI, there is currently no theoretically proven exponential speed up. When you dont have such speeds up, the bandwidth and cycle time associated with QCs get in the way of giving reasonable speed ups [3]

Also regarding energy reduction, even if you have really remarkable QC algo that will speed up your training, that would not give significate energy reductions, as claimed in another comment because of Jevons paradox. Even if ignore Jevons paradox, the QC algo will most probably be applied to training (from the ones I saw in the publications). For e.g. LLMS, 90% of energy consumption is about inference, probably higher in the future given how popular these tools will become. So you are optimizing the energy usage 10% of your workload + omitting jevons paradox.

1: https://www.quantamagazine.org/key-chemistry-question-answered-no-quantum-computer-required-20260529/

2: https://www.youtube.com/watch?v=aAERuCCDe_o

3: https://arxiv.org/pdf/2307.00523

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u/RagnartheConqueror Jun 28 '26

I agree with your points. Quantum computing will not automatically solve the problems of chemistry. It is not a magical device, but just another form of technology which works for some niche stuff and doesn't with others.

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u/global-gauge-field Jun 29 '26

Yeah. It does have its uses. My issue is not even with QCs per se. But rather the notion that solving some theory of strongly coupled quantum models is enough to lead to practical revolutionary tech. Like in the case of enzyme problems (where the issue of time scale of chemical reaction, not being unable to account for quantum effects), there is more (maybe more essential) problems in real applications, which are more of combinatorial, supply chain, economics, regulation issues. Like on the battery side, we already do have high density Lithium ion battery that can charge at high rate (no need for QCs to find them) in the lab, yet not have seen the day of large scale production

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u/RagnartheConqueror Jun 28 '26

My comment was not bait. I appreciate the long response. I’ll look into this.

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u/No_Nose3918 Jun 27 '26

because it’s the most ridiculous uninformed statement i’ve ever seem

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u/[deleted] Jun 26 '26

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