I am confused, since even factoring 21 is apparently so difficult that it "isn’t yet a good benchmark for tracking the progress of quantum computers." [0]
So the "useful quantum computing" that is "imminent" is not the kind of quantum computing that involves the factorization of nearly prime numbers?
Like if you were building one of the first normal computers, how big numbers you can multiply would be a terrible benchmark since once you have figured out how to multiply small numbers its fairly trivial to multiply big numbers. The challenge is making the computer multiply numbers at all.
This isn't a perfect metaphor as scaling is harder in a quantum setting, but we are mostly at the stage where we are trying to get the things to work at all. Once we reach the stage where we can factor small numbers reliably, the amount of time to go from smaller numbers to bigger numbers will be probably be relatively short.
From my limited understanding, that's actually the opposite of the truth.
In QC systems, the engineering "difficulty" scales very badly with the number of gates or steps of the algorithm.
Its not like addition where you can repeat a process in parallel and bam-ALU. From what I understand as a layperson, the size of the inputs is absolutely part of the scaling.
But the reason factoring numbers is used as the quantum benchmark is exactly that we have a quantum algorithm for that problem which is meant to scale better than any known algorithm on a classical computer.
So it seems like it takes an exponentially bigger device to factor 21 than 15, then 35 than 21, and so on, but if I understand right, at some point this levels out and it's only relatively speaking a little harder to factor say 10^30 than 10^29.
Why are we so confident this is true given all of the experience so far trying to scale up from factoring 15 to factoring 21?
This is quite falatious and wrong. The first computers were built in order to solve problems immediately that were already being solved slowly by manual methods. There never was a period where people built computers so slow that they were slower than adding machines and slide rules, just because they seemed cool and might one day be much faster.
Actually yes, how much numbers you can crunch per second and how big they are were among the first benchmarks for actual computers. Also, these prototypes were almost always immediately useful. (Think of the computer that cracked Enigma).
In comparison, there is no realistic path forward for scaling quantum computers. Anyone serious that is not trying to sell you QC will tell you that quantum systems become exponentially less stable the bigger they are and the longer they live. That is a fundamental physical truth. And since they're still struggling to do anything at all with a quantum computer, don't get your hopes up too much.
Once quantum computers are possible, is there actually anything else, any other real world applications, besides breaking crypto and number theory problems that they can do, and do much better than regular computers?
Yes, in fact they might be useful for chemistry simulation long before they are useful for cryptography. Simulations of quantum systems inherently scale better on quantum hardware.
One theoretical use case is “Harvest Now, Decrypt Later” (HNDL) attacks, or “Store Now, Decrypt Later” (SNDL). If an oppressive regime saves encrypted messages now, they can decrypt later when QCs can break RSA and ECC.
It's a good reason to implement post-quantum cryptography.
Wasn't sure if you meant crypto (btc) or cryptography :)
From TFA: ‘One more time for those in the back: the main known applications of quantum computers remain (1) the simulation of quantum physics and chemistry themselves, (2) breaking a lot of currently deployed cryptography, and (3) eventually, achieving some modest benefits for optimization, machine learning, and other areas (but it will probably be a while before those modest benefits win out in practice). To be sure, the detailed list of quantum speedups expands over time (as new quantum algorithms get discovered) and also contracts over time (as some of the quantum algorithms get dequantized). But the list of known applications “from 30,000 feet” remains fairly close to what it was a quarter century ago, after you hack away the dense thickets of obfuscation and hype.’
I realize this is a minority opinion, and goes against all theories of how quantum computing works, but I just cannot believe that nature will allow us to reliably compute with amplitudes as small as 2^-256. I still suspect something will break down as we approach and move below the planck scale.
Fun fact: the Planck mass is about 22 micrograms, about the amount of Vitamin D in a typical multivitamin supplement, and the corresponding derived Planck momentum is 6.5 kg m/s, which is around how hard a child kicks a soccer ball. Nothing inherently special or limiting about these.
I particularly like the end of the post where he compares the history of nuclear fission to the progress on quantum computing. Traditional encryption might already be broken but we have not been told.
In a world where spying on civilian communication of adversaries (and preventing spying on your own civilians) is becoming more critical for national security interests, i suspect that national governments would be lighting more of a fire if they believe their opponents had one.
I really doubt we are anywhere close to this when there has been no published legit prime factorization beyond 21: https://eprint.iacr.org/2025/1237.pdf
Surely if someone managed to factorize a 3 or 4 digits number, they would have published it as it's far enough of weaponization to be worth publishing. To be used to break cryptosystems, you need to be able to factor at least 2048-digits numbers. Even assuming the progress is linear with respect to the number of bits in the public key (this is the theoretical lower bound but assume hardware scaling is itself linear, which doesn't seem to be the case), there's a pretty big gap between 5 and 2048 and the fact that no-one has ever published any significant result (that is, not a magic trick by choosing the number in a way that makes the calculation trivial, see my link above) showing any process in that direction suggest we're not in any kind of immediate threat.
The reality is that quantum computing is still very very hard, and very very far from being able what is theoretically possible with them.
Zero money take: quantum computing looks like a bunch of refrigerator companies.
The fact that error correction seems to be struggling implies unaccounted for noise that is not heat. Who knows maybe gravitational waves heck your setup no matter what you do!
As someone that works in quantum computing research both academic and private, no it isn't imminent in my understanding of the word, but it will happen. We are still at that point whereby we are comparable to 60's general computing development. Many different platforms and we have sort of decided on the best next step but we have many issues still to solve. A lot of the key issues have solutions, the problem is more getting everyone to focus in the right direction, which also will mean when funding starts to focus in the right direction. There are snake oil sellers right now and life will be imminently easier when they are removed.
Wouldn't the comparison be more like the 1920s for computing. We had useful working computers in the 1940s working on real problems doing what was not possible before hand. By the 1950s we had computers doing Nuclear bomb simulations and the 1960s we had computers in banks doing accounting and inventory. So we had computers by then, not in homes, but we had them. In the 1920s we had mechanical calculators and theories on computation emerging but not a general purpose computer. Until we have a quantum computer doing work at least at the level of a digital computer I can't really believe it being the 1960s.
I'm not going to pretend that I am that knowledgeable on classic computing history from that time period. I was primarily going off the fact the semi conductor was built in the late 40's, and I would say we have the quantum version of that in both qubit and photonic based computing and they work and we have been developing on them for some time now. The key difference is that there are many more steps to get to the stage of making them useful. A transistor becamse useful extremely quickly and well in Quantum computing, these just haven't quite yet.
Not to be snarky, but how is it comparable to 60's computing? There was a commercial market for computers and private and public sector adoption and use in the 60s.
There is private sector adoption and planning now of specific single purpose focused quantum devices in military and security settings. They work and exist although I do not believe they are installed. I may be wrong on the exact date, as my classical computer knowledge isn't spot on. The point I was trying to make was that we have all the bits we need. We have the ability to make the photonic quantum version (which spoiler alert is where the focus needs to move to over the qubit method of quantum computing) of a transistor, so we have hit the 50's at least. The fundamentals at this point won't change. What will change is how they are put together and how they are made durable.
- Too few researchers, as in my area of quantum computing. I would state there is one other group that has any academic rigour, and is actually making significant and important progress. The two other groups are using non reproducible results for credit and funding for private companies. You have FAANG style companies also doing research, and the research that comes out still is clearly for funding. It doesn't stand up under scrutiny of method (there usually isn't one although that will soon change as I am in the process of producing a recipe to get to the point we are currently at which is as far as anyone is at) and repeatability.
- Too little progress. Now this is due to the research focus being spread too thin. We have currently the classic digital (qubit) vs analogue (photonic) quantum computing fight, and even within each we have such broad variations of where to focus. Therefore each category is still really just at the start as we are going in so many different directions. We aren't pooling our resources and trying to make progress together. This is also where a lack of openness regarding results and methods harms us. Likewise a lack of automation. Most significant research is done by human hand, which means building on it at a different research facility often requires learning off the person who developed the method in person if possible or at worse, just developing a method again which is a waste of time. If we don't see the results, the funding won't be there. Obviously classical computing eventually found a use case and then it became useful for the public but I fear we may not get to that stage as we may take too long.
As an aside, we may also get to the stage whereby, it is useful but only in a military/security setting. I have worked on a security project (I was not bound by any NDA surprisingly but I'm still wary) featuring a quantum setup, that could of sorts be comparable to a single board computer (say of an ESP32), although much larger. There is some value to it, and that particular project could be implemented into security right now (I do not believe it has or will, I believe it was viability) and isn't that far off. But that particular project has no other uses, outside of the military/security.
Did anyone else read the last two paragraphs as “I AM NOT ALLOWED TO TELL YOU THINGS YOU SHOULD BE VERY CONCERNED ABOUT” in bright flashing warning lights or is it just me?
I don't think he is saying that. As I said in my other comment here I think he is just drawing a potential parallel to other historic work that was done in a private(secret) domain. The larger point is we simply don't know so it's best to act in a way that even if it hasn't been done already it certainly seems like it will be broken. Hence the move to Post-Quantum Cryptography is probably a good idea!
It is more, many companies can't do what they claim to do, or they have done it once at best and had no more consistency. I sense most companies in the quantum computing space right now are of this ilk. As someone that works in academic and private quantum computing research, repeatability and methodology are severely lacking, which always rings alarm bells. Some companies are funded off the back of one very poor quality research paper, reviewed by people who are not experts, that then leads to a company that looks professional but behind the scenes I would imagine are saying Oh shit, now we actually have to do this thing we said we could do.
So the "useful quantum computing" that is "imminent" is not the kind of quantum computing that involves the factorization of nearly prime numbers?
[0] https://algassert.com/post/2500
Like if you were building one of the first normal computers, how big numbers you can multiply would be a terrible benchmark since once you have figured out how to multiply small numbers its fairly trivial to multiply big numbers. The challenge is making the computer multiply numbers at all.
This isn't a perfect metaphor as scaling is harder in a quantum setting, but we are mostly at the stage where we are trying to get the things to work at all. Once we reach the stage where we can factor small numbers reliably, the amount of time to go from smaller numbers to bigger numbers will be probably be relatively short.
In QC systems, the engineering "difficulty" scales very badly with the number of gates or steps of the algorithm.
Its not like addition where you can repeat a process in parallel and bam-ALU. From what I understand as a layperson, the size of the inputs is absolutely part of the scaling.
So it seems like it takes an exponentially bigger device to factor 21 than 15, then 35 than 21, and so on, but if I understand right, at some point this levels out and it's only relatively speaking a little harder to factor say 10^30 than 10^29.
Why are we so confident this is true given all of the experience so far trying to scale up from factoring 15 to factoring 21?
In comparison, there is no realistic path forward for scaling quantum computers. Anyone serious that is not trying to sell you QC will tell you that quantum systems become exponentially less stable the bigger they are and the longer they live. That is a fundamental physical truth. And since they're still struggling to do anything at all with a quantum computer, don't get your hopes up too much.
https://en.wikipedia.org/wiki/Quantum_computational_chemistr...
It's a good reason to implement post-quantum cryptography.
Wasn't sure if you meant crypto (btc) or cryptography :)
Surely if someone managed to factorize a 3 or 4 digits number, they would have published it as it's far enough of weaponization to be worth publishing. To be used to break cryptosystems, you need to be able to factor at least 2048-digits numbers. Even assuming the progress is linear with respect to the number of bits in the public key (this is the theoretical lower bound but assume hardware scaling is itself linear, which doesn't seem to be the case), there's a pretty big gap between 5 and 2048 and the fact that no-one has ever published any significant result (that is, not a magic trick by choosing the number in a way that makes the calculation trivial, see my link above) showing any process in that direction suggest we're not in any kind of immediate threat.
The reality is that quantum computing is still very very hard, and very very far from being able what is theoretically possible with them.
The fact that error correction seems to be struggling implies unaccounted for noise that is not heat. Who knows maybe gravitational waves heck your setup no matter what you do!
If you were to guess what reasons there might be that it WON’T happen, what would some of those reasons be?
- Too few researchers, as in my area of quantum computing. I would state there is one other group that has any academic rigour, and is actually making significant and important progress. The two other groups are using non reproducible results for credit and funding for private companies. You have FAANG style companies also doing research, and the research that comes out still is clearly for funding. It doesn't stand up under scrutiny of method (there usually isn't one although that will soon change as I am in the process of producing a recipe to get to the point we are currently at which is as far as anyone is at) and repeatability.
- Too little progress. Now this is due to the research focus being spread too thin. We have currently the classic digital (qubit) vs analogue (photonic) quantum computing fight, and even within each we have such broad variations of where to focus. Therefore each category is still really just at the start as we are going in so many different directions. We aren't pooling our resources and trying to make progress together. This is also where a lack of openness regarding results and methods harms us. Likewise a lack of automation. Most significant research is done by human hand, which means building on it at a different research facility often requires learning off the person who developed the method in person if possible or at worse, just developing a method again which is a waste of time. If we don't see the results, the funding won't be there. Obviously classical computing eventually found a use case and then it became useful for the public but I fear we may not get to that stage as we may take too long.
As an aside, we may also get to the stage whereby, it is useful but only in a military/security setting. I have worked on a security project (I was not bound by any NDA surprisingly but I'm still wary) featuring a quantum setup, that could of sorts be comparable to a single board computer (say of an ESP32), although much larger. There is some value to it, and that particular project could be implemented into security right now (I do not believe it has or will, I believe it was viability) and isn't that far off. But that particular project has no other uses, outside of the military/security.
once someone makes a widget that extracts an RSA payload, their govt will seize, spend & scale
they will try to keep it quiet but they will start a spending spree that will be visible from space
Either way he must have known people would read it like you did when he wrote that; so we can safely assume it's boasting at the very least.
> This is the clearest warning that I can offer in public right now about the urgency of migrating to post-quantum cryptosystems...
That has a clear implication that he knows something that he doesn't want to say publically