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More on whether useful quantum computing is “imminent”

152 points by A_D_E_P_T 10mo ago

prof-dr-ir 10mo ago
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? [0] https://algassert.com/post/2500 https://algassert.com/post/2500
- bawolff 10mo ago
  I always find this argument a little silly. 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.
  - jvanderbot 10mo ago
    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.
    - dmurray 10mo ago
      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?
      - bawolff 10mo ago
        > 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? I don't think we have any "real" experience scaling from 15 to 21. Or at least not in the way shor's algorithm would be implemented in practise on fault tolerant qubits. We haven't even done 15 yet in a "real" way yet. I susect the amount of time to factor 15 on fault tolerant qubits will be a lot longer than the time to go from 15 to 21.
      - pclmulqdq 10mo ago
        The algorithm in question is a hypothetical algorithm for a hypothetical computer with certain properties. The properties in question are assumed to be cheap. In the case of quantum algorithms in BQP, though, one of those properties is SNR of analog calculations (which is assumed to be infinite). SNR, as a general principle, is known to scale really poorly.
        bawolff 10mo ago
        > In the case of quantum algorithms in BQP, though, one of those properties is SNR of analog calculations (which is assumed to be infinite). SNR, as a general principle, is known to scale really poorly. As far as i understand, that isn't an assumption. The assumption is that the SNR of logical (error-corrected) qubits is near infinite, and that such logical qubits can be constructed from noisey physical qubits.
        pclmulqdq 10mo ago
        There are several properties that separate real quantum computers from the "BQP machine," including decoherence and SNR. Error-correction of qubits is mainly aimed at decoherence, but I'm not sure it really improves SNR of gates on logical qubits. SNR dictates how precisely you can manipulate the signal (these are a sort of weird kind of analog computer), and the QFTs involved in Shor's algorithm need some very precise rotations of qubits. Noise in the operation creates an error in that rotation angle. If your rotation is bad to begin with, I'm not sure the error correction actually helps.
        10mo ago
  - sfpotter 10mo ago
    The fact that it does appear to be so difficult to scale things up would suggest that the argument isn't silly.
  - thrance 10mo ago
    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.
    - bawolff 10mo ago
      > 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. If what you are saying is that error rates increase exponentially such that quantum error correction can never correct more errors than it introduces, i don't think that is a widely accepted position in the field.
      - fragmede 10mo ago
        People who believed that would opt out of being in the field, though. No?
    - amenhotep 10mo ago
      That would be the bombe, which didn't really crunch numbers at all, but was an electromechanical contraption to automate physically setting Enigma rotors to enumerate what combinations were possible matches.
  - dboreham 10mo ago
    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.
    - bawolff 10mo ago
      Charles babbage started on the difference engine in 1819. It took a very long time after that before computers were useful.
      - bawolff 10mo ago
        Additionally, part of the problem was that metal working at the time wasn't really advanced enough to make the required parts to the necessary precision at a reasonable price. Which sounds really quite similar to how modern quantum computers are right at the edge of current engineering technology.
- upofadown 10mo ago
  Perhaps? The sort of quantum computers that people are talking about now are not general purpose. So you might be able to make a useful quantum computer that is not Shor's algorithm.
  - gsf_emergency_6 10mo ago
    Simulating the Hubbard model for superconductors at large scales is significantly more likely to happen sooner than factoring RSA-2048 with Shor’s algorithm. Google have been working on this for years Don't ask me if they've the top supercomputers beat, ask Gemini :)
    - tomalbrc 10mo ago
      Gemini hallucinated me a wild answer.
  - bawolff 10mo ago
    I don't think that's correct, the research projects the article is talking about all seem to aim at making general purpose quantum computers eventually. Obviously they haven't succeded yet, but general purpose does seem to be what they are talking about.
- Strilanc 10mo ago
  Factoring will be okay for tracking progress later; it's just a bad benchmark now. Factoring benchmarks have little visibility into fault tolerance spinning up, which is the important progress right now. Factoring becoming a reasonable benchmark is strongly related to quantum computing becoming useful.
  - prof-dr-ir 10mo ago
    > Factoring becoming a reasonable benchmark is strongly related to quantum computing becoming useful. Either this relation is not that strong, or factoring should "imminently" become a reasonable benchmark, or useful quantum computing cannot be "imminent". So which one is it? I think you are the author of the blogpost I linked to? Did I maybe interpret it too negatively, and was it not meant to suggest that the second option is still quite some time away?
    - adgjlsfhk1 10mo ago
      Under a Moore's law-like scenario, factoring 21 happens only about ~5 years before factoring a 1024 bit number. With all the optimizations, factoring an n bit number only requires ~n logical qbits, but most of those optimizations only work for large n, so 21 is only ~5 doubles away from 2^1024. the other problem is that factoring 21 is so easy that it actually makes it harder to prove you've factored it with a functional quantum computer. for big numbers, your program can fail 99% of the time because if you get the result once, you prove that the algorithm worked. 21 is small enough that it's hard not to factor, so demonstrating that you've factored it with a qc is fairly hard. I wouldn't be surprised as a result if the first number publicly factored by a quantum computer (using error correction) was in the thousands instead of 21. By using a number that is not absolutely tiny, it becomes a lot easier to show that the system works.
- unparagoned 10mo ago
  Basically qc are so far from ever doing a useful computation we need other benchmarks to measure progress. We need to be thinking in timelines of our lifetime not 5 years
bahmboo 10mo ago
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.
- bawolff 10mo ago
  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.
  - the8472 10mo ago
    NSA is pushing for PQ algos.
  - mvkel 10mo ago
    They absolutely are. NSA is obsessed with post-quantum projects atm
    - tyre 10mo ago
      But is this because they are already needed or because they want to preserve encryption for past and present data post-quantum?
      - mvkel 10mo ago
        The latter
    - GrilledChips 10mo ago
      tbh they could just be pushing for people to adopt newer, less-tested, weaker algorithms. switch from something battle-hardened to the QuantResist2000 algorithm which they've figured out how to break with lattice reduction and a couple of GPUs like those minecraft guys did.
ktallett 10mo ago
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.
- andsoitis 10mo ago
  > it will happen. If you were to guess what reasons there might be that it WON’T happen, what would some of those reasons be?
  - ktallett 10mo ago
    So in my view, the issues I think about now are: - 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.
eightysixfour 10mo ago
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?
- William_BB 10mo ago
  Just you
- ktallett 10mo ago
  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.
- bahmboo 10mo ago
  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!
  - griffzhowl 10mo ago
    Aaronson says: > 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
    - machinationu 10mo ago
tromp 10mo ago
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.
- semi-extrinsic 10mo ago
  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.
  - ttoinou 10mo ago
    If you look at Planck units or any dimensionless set of physical units, you will see that mass stands apart from others units. There’s like a factor 10^15 or something like this, i.e. we can’t scale all physical units to be around the same values, something is going with mass and gravity that makes it different than others
    - adrian_b 10mo ago
      After computing in 1899 for the first time the value of what is now named "Planck's constant" (despite the fact that Planck has computed both constants that are now named "Boltzmann's constant" and "Planck's constant"), Planck has immediately realized that this provides an extra value, besides those previously known, which can be used for the definition of a natural unit of measurement. Nevertheless, Planck did not understand well enough the requirements for a good system of fundamental units of measurement (because he was a theoretician, not an experimentalist; he had computed his constants by a better mathematical treatment of the experimental data provided by Paschen), so he did not find any good way to integrate Planck's constant in a system of fundamental units and he has made the same mistake made by Stoney 25 years before him (after computing the value of the elementary electric charge) and he has chosen the wrong method for defining the unit of mass among two variants previously proposed by Maxwell (the 2 variants were deriving the unit of mass from the mass of some atom or molecule and deriving the unit of mass from the Newtonian constant of gravitation). All dimensionless systems of fundamental units are worthless in practice (because they cause huge uncertainties in all values of absolute measurements) and they do not have any special theoretical significance (for now; such a significance would appear only if it became possible to compute exactly from theory the values of the 2 constants of the electromagnetic interaction and gravitational interaction, instead of measuring them through experiments; until now nobody had any useful idea for a theory that could do such things). For the number of independently chosen fundamental units of measurement there exists an optimum value and the systems with either more or fewer fundamental units lead to greater uncertainties in the values of the physical quantities and to superfluous computations in the mathematical models. The dimensionless systems of units are not simpler, but more complicated, so attempting to eliminate the independently chosen fundamental units is the wrong goal when searching for the best system of units of measurement. My point is that the values of the so-called "Planck units" have absolutely no physical significance, therefore it is extremely wrong to use them in any reasoning about what is possible or impossible or about anything else. The "Planck units" are not unique, there also exists a very similar system of "Stoney units", proposed a quarter of century before the "Planck units", where the values of the units are different, and there are also other variants of dimensionless systems of units proposed later. None of them is better than the others and all are bad, the worst defect being that the huge experimental uncertainties from measuring the value of the Newtonian constant of gravitation are moved from that single value into the values of all unrelated physical quantities, so that no absolute value can be known precisely, but only the ratios between quantities of the same kind. In a useful system of fundamental units, for all units there are "natural" choices, except for one, which is the scale factor of the spatio-temporal units. For this scale factor of space-time, in the current state of knowledge there is no special value that can be distinguished from other arbitrary choices, so it is chosen solely based on the practical ease of building standards of frequency and wave-number that have adequate reproducibility and stability. The only historical value of the "Planck units" is that they provide a good example of how one should NOT choose a system of units of measurement. The fact that they are still frequently mentioned by some people in any other context than criticizing such a system just demonstrates the very sad state of physics education, where no physics textbook includes an adequate presentation of the foundation of physics, which is the theory of the measurement of physical quantities. One century and a half ago, Maxwell began his treatise on electricity and magnetism with a very good exposition of the state of metrology at that time, but later physics textbooks have become less and less rigorous, instead of improving.
Aardwolf 10mo ago
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?
- comicjk 10mo ago
  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. https://en.wikipedia.org/wiki/Quantum_computational_chemistry https://en.wikipedia.org/wiki/Quantum_computational_chemistr...
  - GrilledChips 10mo ago
    More recently it's turned out that quantum computers are less useful for molecular simulation than previously thought. See: https://www.youtube.com/watch?v=pDj1QhPOVBo https://www.youtube.com/watch?v=pDj1QhPOVBo The video is essentially an argument from the software side (ironically she thinks the hardware side is going pretty well). Even if the hardware wasn't so hard to build or scale, there are surprisingly few problems where quantum algorithms have turned out to be useful.
    - comicjk 10mo ago
      It is tough to beat classical computers. They work really well, and a huge amount of time (including some of mine) has gone into developing fast algorithms for them to do things they're not naturally fast at, such as quantum chemistry.
    - oasisaimlessly 10mo ago
      At 15:00, she says "quantum computers are surprisingly good at [...] quantum simulations [of electron behavior]", which would seem to contradict you.
      - deleted 10mo ago
        [deleted]
tgi42 10mo ago
I worked in this field for years and helped build one of the recognizable companies. It has been disappointing to see, once again, promising science done in earnest be taken over by grifters. We knew many years ago that it was going to take FAR fewer qubits to crack encryption than pundits (and even experts) believed.
jasonmarks_ 10mo ago
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!
willmadden 10mo ago
We'll know when all of the old Bitcoin P2PK addresses and transacted from addresses are swept.
- GrilledChips 10mo ago
  the funny thing is that nobody will ever do that. The moment someone uses quantum computing or any other technology to crack bitcoin in a visible way, the coins they just gave to themselves become worthless because confidence collapses.
  - pona-a 10mo ago
    There are some Bitcoin puzzles or old wallets that give some plausible deniability.
  - Traubenfuchs 10mo ago
    Well, they wouldn't go for the trillion dollar wale addresses. They would hack random, long unused, dead addresses holding 5 figure amounts and slowly convert those to money. They would eventually start to significantly lower the value and eventually crash bitcoin if too greedy, but could get filthy rich.
Traubenfuchs 10mo ago
Cloud providers will love it when we will need to buy more compute and memory for post quantum TSL.
nacozarina 10mo ago
another late signal will be a funding spike 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
cubefox 10mo ago
This sounds slightly alarming: > I’m going to close this post with a warning. When Frisch and Peierls wrote their now-famous memo in March 1940, estimating the mass of Uranium-235 that would be needed for a fission bomb, they didn’t publish it in a journal, but communicated the result through military channels only. As recently as February 1939, Frisch and Meitner had published in Nature their theoretical explanation of recent experiments, showing that the uranium nucleus could fission when bombarded by neutrons. But by 1940, Frisch and Peierls realized that the time for open publication of these matters had passed. > Similarly, at some point, the people doing detailed estimates of how many physical qubits and gates it’ll take to break actually deployed cryptosystems using Shor’s algorithm are going to stop publishing those estimates, if for no other reason than the risk of giving too much information to adversaries. Indeed, for all we know, that point may have been passed already. This is the clearest warning that I can offer in public right now about the urgency of migrating to post-quantum cryptosystems, a process that I’m grateful is already underway. Does anyone know how much underway it is? Do we need to worry that the switch away from RSA won't be broadly deployed before quantum decryption becomes available?
- JanisErdmanis 10mo ago
  From analytical arguments considering a rather generic error type, we already know that for the Shor algorithm to produce a useful result, the error rate with the number of logical qubits needs to decrease as ~n^(-1/3), where `n` is the number of bits in the number [1]. This estimate, however, assumes that interaction can be turned on between arbitrary two qubits. In practice, we can only do nearest-neighbour interactions on a square lattice, and we need to simulate the interaction between two arbitrary qubits by repeated application of SWAP gates, mangling the interaction through as in the 15th puzzle. This two-qubit simulation would add about `n` SWAP gates, which would then multiply the noise factor by the same factor, hence now we need an error rate for logical qubits on a square lattice to be around ~n^(-4/3) Now comes the error correction. The estimates are somewhat hard to make here, as they depend on the sensitivity of the readout mechanism, but for example let’s say a 10-bit number can be factored with a logical qubit error rate of 10^{-5}. Then we apply a surface code that scales exponentially, reducing the error rate by 10 times with 10 physical qubits, which we could express as ~1/10^{m/10}, where m is the number of physical qubits (which is rather optimistic). Putting in the numbers, it would follow that we need 40 physical qubits for a logical qubit, hence in total 400k physical qubits. That may sound reasonable, but then we made the assumption that while manipulating the individual physical qubits, decoherence for each individual qubit does not happen while they are waiting for their turn. This, in fact, scales poorly with the number of qubits on the chip because physical constraints limit the number of coaxial cables that can be attached, hence multiplexing of control signals and hence the waiting of the qubits is imminent. This waiting is even more pronounced in the quantum computer cluster proposals that tend to surface sometimes. [1]: https://link.springer.com/article/10.1007/s11432-023-3961-3 https://link.springer.com/article/10.1007/s11432-023-3961-3
hellobluelings 10mo ago
[dead]
osn9363739 10mo ago
This is the worst quantum computing will ever be.
- AlexandrB 10mo ago
  You assume no civilizational collapse is in our future.
  - qgin 10mo ago
    Tbh this reply works for pretty much anything anyone ever says
    - osn9363739 10mo ago
      I was attempting a sarcastic jab at the whole "this is the worst AI will ever be". Yet tech (or anything really) will often hit a wall, and be about as good as it's ever going to get.
- ktallett 10mo ago
  That vastly depends on if we choose to go in the right direction.
noname120 10mo ago
I can’t believe how the very first line of the article is a grotesque strawman. Tbh I expected better from Scott Aaronson.
- lukeasrodgers 10mo ago
  Could you elaborate as you why you think it is a grotesque strawman? It doesn’t strike me as such, even on rereading.
- hiddencost 10mo ago
  The guy who spends most of his time posting either in favor of genocide or about how he got cancelled for being a misogynist? He's an excellent scientist but not a calm person.
sallveburrpi 10mo ago
So summary is that useful quantum computing is definitely not imminent (as in probably happening in the next 10-20 years) - or am I misreading ?
ursAxZA 10mo ago
Which one ends up being more accurate — quantum-computing forecasts or fashion-magazine trend predictions?
Antibabelic 10mo ago
Is it possible that practical quantum computing is actually impossible and we only think it is because of our incomplete understanding of physics?
yoan9224 10mo ago
Aaronson's take is characteristically grounded. The Willow chip announcement was impressive technically but the media coverage predictably overshot into "RSA is dead" territory when the actual achievement was improving error correction rates. The relevant timeline question is: when do quantum computers solve problems faster than classical computers for commercially useful tasks (not just contrived benchmarks)? The error correction milestone matters because it's the gate to scaling. Previous quantum systems had error rates that increased faster than you could add qubits, making large-scale quantum computing impossible. If Willow actually demonstrates below-threshold error rates at scale (I'd want independent verification), that unblocks the path to 1000+ logical qubit systems. But we're still probably 5-7 years from "useful quantum advantage" on problems like drug discovery or materials simulation. The economic argument is underrated. Even if quantum computers achieve theoretical advantage, they need to beat rapidly improving classical algorithms running on cheaper hardware. Every year we delay, classical GPUs get faster and quantum algorithms get optimized for near-term noisy hardware. The crossover point might be narrower than people expect. What I find fascinating is the potential for hybrid classical-quantum algorithms where quantum computers handle specific subroutines (like sampling from complex distributions or solving linear algebra problems) while classical computers do pre/post-processing. That's probably the first commercial application - not replacing classical computers entirely but augmenting them for specific bottlenecks. Imagine a drug discovery pipeline where the 3D protein folding simulation runs on quantum hardware but everything else is classical.
- OkayPhysicist 10mo ago
  First? Try only. I'd be willing to wager a sizeable amount of money that no one save for a few niche research institutions trying to improve quantum computing will ever be using fully quantum setups. QC is not a panacea. There are a handful of algorithms that are in BQP-P, and most of those aren't really used in tasks I would imagine the average person frequently engaging in. Simultaneously, quantum computers necessarily have complications that classical computers lack. Combined, I doubt people will be using purely quantum computers ever.
ProllyInfamous 10mo ago
Vanderbilt University [0] is about to open a "quantum research graduate studies" campus, somewhere near Chattanooga, Tennessee. I have a degree in chemistry from that institution, and don't have a clue what this means beyond the $1,000,000,000 economic impact this facility is supposed to make upon our fair city, over the next decade. [•] <https://quantumzeitgeist.com/vanderbilt-university-quantum-quantum-research/ https://quantumzeitgeist.com/vanderbilt-university-quantum-q...> [0] In partnership with our government-subsidized "commercial quantum-ready" fiber network, EPB

152 points by A_D_E_P_T 10mo ago

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? [0] https://algassert.com/post/2500 https://algassert.com/post/2500

bawolff 10mo ago
I always find this argument a little silly. 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.
- jvanderbot 10mo ago
  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.
  - dmurray 10mo ago
    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?
    - bawolff 10mo ago
      > 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? I don't think we have any "real" experience scaling from 15 to 21. Or at least not in the way shor's algorithm would be implemented in practise on fault tolerant qubits. We haven't even done 15 yet in a "real" way yet. I susect the amount of time to factor 15 on fault tolerant qubits will be a lot longer than the time to go from 15 to 21.
    - pclmulqdq 10mo ago
      The algorithm in question is a hypothetical algorithm for a hypothetical computer with certain properties. The properties in question are assumed to be cheap. In the case of quantum algorithms in BQP, though, one of those properties is SNR of analog calculations (which is assumed to be infinite). SNR, as a general principle, is known to scale really poorly.
      - bawolff 10mo ago
        > In the case of quantum algorithms in BQP, though, one of those properties is SNR of analog calculations (which is assumed to be infinite). SNR, as a general principle, is known to scale really poorly. As far as i understand, that isn't an assumption. The assumption is that the SNR of logical (error-corrected) qubits is near infinite, and that such logical qubits can be constructed from noisey physical qubits.
        pclmulqdq 10mo ago
        There are several properties that separate real quantum computers from the "BQP machine," including decoherence and SNR. Error-correction of qubits is mainly aimed at decoherence, but I'm not sure it really improves SNR of gates on logical qubits. SNR dictates how precisely you can manipulate the signal (these are a sort of weird kind of analog computer), and the QFTs involved in Shor's algorithm need some very precise rotations of qubits. Noise in the operation creates an error in that rotation angle. If your rotation is bad to begin with, I'm not sure the error correction actually helps.
        10mo ago
- sfpotter 10mo ago
  The fact that it does appear to be so difficult to scale things up would suggest that the argument isn't silly.
- thrance 10mo ago
  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.
  - bawolff 10mo ago
    > 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. If what you are saying is that error rates increase exponentially such that quantum error correction can never correct more errors than it introduces, i don't think that is a widely accepted position in the field.
    - fragmede 10mo ago
      People who believed that would opt out of being in the field, though. No?
  - amenhotep 10mo ago
    That would be the bombe, which didn't really crunch numbers at all, but was an electromechanical contraption to automate physically setting Enigma rotors to enumerate what combinations were possible matches.
- dboreham 10mo ago
  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.
  - bawolff 10mo ago
    Charles babbage started on the difference engine in 1819. It took a very long time after that before computers were useful.
    - bawolff 10mo ago
      Additionally, part of the problem was that metal working at the time wasn't really advanced enough to make the required parts to the necessary precision at a reasonable price. Which sounds really quite similar to how modern quantum computers are right at the edge of current engineering technology.
upofadown 10mo ago
Perhaps? The sort of quantum computers that people are talking about now are not general purpose. So you might be able to make a useful quantum computer that is not Shor's algorithm.
- gsf_emergency_6 10mo ago
  Simulating the Hubbard model for superconductors at large scales is significantly more likely to happen sooner than factoring RSA-2048 with Shor’s algorithm. Google have been working on this for years Don't ask me if they've the top supercomputers beat, ask Gemini :)
  - tomalbrc 10mo ago
    Gemini hallucinated me a wild answer.
- bawolff 10mo ago
  I don't think that's correct, the research projects the article is talking about all seem to aim at making general purpose quantum computers eventually. Obviously they haven't succeded yet, but general purpose does seem to be what they are talking about.
Strilanc 10mo ago
Factoring will be okay for tracking progress later; it's just a bad benchmark now. Factoring benchmarks have little visibility into fault tolerance spinning up, which is the important progress right now. Factoring becoming a reasonable benchmark is strongly related to quantum computing becoming useful.
- prof-dr-ir 10mo ago
  > Factoring becoming a reasonable benchmark is strongly related to quantum computing becoming useful. Either this relation is not that strong, or factoring should "imminently" become a reasonable benchmark, or useful quantum computing cannot be "imminent". So which one is it? I think you are the author of the blogpost I linked to? Did I maybe interpret it too negatively, and was it not meant to suggest that the second option is still quite some time away?
  - adgjlsfhk1 10mo ago
    Under a Moore's law-like scenario, factoring 21 happens only about ~5 years before factoring a 1024 bit number. With all the optimizations, factoring an n bit number only requires ~n logical qbits, but most of those optimizations only work for large n, so 21 is only ~5 doubles away from 2^1024. the other problem is that factoring 21 is so easy that it actually makes it harder to prove you've factored it with a functional quantum computer. for big numbers, your program can fail 99% of the time because if you get the result once, you prove that the algorithm worked. 21 is small enough that it's hard not to factor, so demonstrating that you've factored it with a qc is fairly hard. I wouldn't be surprised as a result if the first number publicly factored by a quantum computer (using error correction) was in the thousands instead of 21. By using a number that is not absolutely tiny, it becomes a lot easier to show that the system works.
unparagoned 10mo ago
Basically qc are so far from ever doing a useful computation we need other benchmarks to measure progress. We need to be thinking in timelines of our lifetime not 5 years

bahmboo 10mo ago

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.

bawolff 10mo ago
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.
- the8472 10mo ago
  NSA is pushing for PQ algos.
- mvkel 10mo ago
  They absolutely are. NSA is obsessed with post-quantum projects atm
  - tyre 10mo ago
    But is this because they are already needed or because they want to preserve encryption for past and present data post-quantum?
    - mvkel 10mo ago
      The latter
  - GrilledChips 10mo ago
    tbh they could just be pushing for people to adopt newer, less-tested, weaker algorithms. switch from something battle-hardened to the QuantResist2000 algorithm which they've figured out how to break with lattice reduction and a couple of GPUs like those minecraft guys did.

ktallett 10mo ago

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.

andsoitis 10mo ago
> it will happen. If you were to guess what reasons there might be that it WON’T happen, what would some of those reasons be?
- ktallett 10mo ago
  So in my view, the issues I think about now are: - 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.

eightysixfour 10mo ago

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?

William_BB 10mo ago
Just you
ktallett 10mo ago
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.
bahmboo 10mo ago
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!
- griffzhowl 10mo ago
  Aaronson says: > 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
  - machinationu 10mo ago

tromp 10mo ago

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.

semi-extrinsic 10mo ago
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.
- ttoinou 10mo ago
  If you look at Planck units or any dimensionless set of physical units, you will see that mass stands apart from others units. There’s like a factor 10^15 or something like this, i.e. we can’t scale all physical units to be around the same values, something is going with mass and gravity that makes it different than others
  - adrian_b 10mo ago
    After computing in 1899 for the first time the value of what is now named "Planck's constant" (despite the fact that Planck has computed both constants that are now named "Boltzmann's constant" and "Planck's constant"), Planck has immediately realized that this provides an extra value, besides those previously known, which can be used for the definition of a natural unit of measurement. Nevertheless, Planck did not understand well enough the requirements for a good system of fundamental units of measurement (because he was a theoretician, not an experimentalist; he had computed his constants by a better mathematical treatment of the experimental data provided by Paschen), so he did not find any good way to integrate Planck's constant in a system of fundamental units and he has made the same mistake made by Stoney 25 years before him (after computing the value of the elementary electric charge) and he has chosen the wrong method for defining the unit of mass among two variants previously proposed by Maxwell (the 2 variants were deriving the unit of mass from the mass of some atom or molecule and deriving the unit of mass from the Newtonian constant of gravitation). All dimensionless systems of fundamental units are worthless in practice (because they cause huge uncertainties in all values of absolute measurements) and they do not have any special theoretical significance (for now; such a significance would appear only if it became possible to compute exactly from theory the values of the 2 constants of the electromagnetic interaction and gravitational interaction, instead of measuring them through experiments; until now nobody had any useful idea for a theory that could do such things). For the number of independently chosen fundamental units of measurement there exists an optimum value and the systems with either more or fewer fundamental units lead to greater uncertainties in the values of the physical quantities and to superfluous computations in the mathematical models. The dimensionless systems of units are not simpler, but more complicated, so attempting to eliminate the independently chosen fundamental units is the wrong goal when searching for the best system of units of measurement. My point is that the values of the so-called "Planck units" have absolutely no physical significance, therefore it is extremely wrong to use them in any reasoning about what is possible or impossible or about anything else. The "Planck units" are not unique, there also exists a very similar system of "Stoney units", proposed a quarter of century before the "Planck units", where the values of the units are different, and there are also other variants of dimensionless systems of units proposed later. None of them is better than the others and all are bad, the worst defect being that the huge experimental uncertainties from measuring the value of the Newtonian constant of gravitation are moved from that single value into the values of all unrelated physical quantities, so that no absolute value can be known precisely, but only the ratios between quantities of the same kind. In a useful system of fundamental units, for all units there are "natural" choices, except for one, which is the scale factor of the spatio-temporal units. For this scale factor of space-time, in the current state of knowledge there is no special value that can be distinguished from other arbitrary choices, so it is chosen solely based on the practical ease of building standards of frequency and wave-number that have adequate reproducibility and stability. The only historical value of the "Planck units" is that they provide a good example of how one should NOT choose a system of units of measurement. The fact that they are still frequently mentioned by some people in any other context than criticizing such a system just demonstrates the very sad state of physics education, where no physics textbook includes an adequate presentation of the foundation of physics, which is the theory of the measurement of physical quantities. One century and a half ago, Maxwell began his treatise on electricity and magnetism with a very good exposition of the state of metrology at that time, but later physics textbooks have become less and less rigorous, instead of improving.

Aardwolf 10mo ago

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?

comicjk 10mo ago
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. https://en.wikipedia.org/wiki/Quantum_computational_chemistry https://en.wikipedia.org/wiki/Quantum_computational_chemistr...
- GrilledChips 10mo ago
  More recently it's turned out that quantum computers are less useful for molecular simulation than previously thought. See: https://www.youtube.com/watch?v=pDj1QhPOVBo https://www.youtube.com/watch?v=pDj1QhPOVBo The video is essentially an argument from the software side (ironically she thinks the hardware side is going pretty well). Even if the hardware wasn't so hard to build or scale, there are surprisingly few problems where quantum algorithms have turned out to be useful.
  - comicjk 10mo ago
    It is tough to beat classical computers. They work really well, and a huge amount of time (including some of mine) has gone into developing fast algorithms for them to do things they're not naturally fast at, such as quantum chemistry.
  - oasisaimlessly 10mo ago
    At 15:00, she says "quantum computers are surprisingly good at [...] quantum simulations [of electron behavior]", which would seem to contradict you.
    - deleted 10mo ago
      [deleted]

tgi42 10mo ago

I worked in this field for years and helped build one of the recognizable companies. It has been disappointing to see, once again, promising science done in earnest be taken over by grifters. We knew many years ago that it was going to take FAR fewer qubits to crack encryption than pundits (and even experts) believed.

jasonmarks_ 10mo ago

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!

willmadden 10mo ago

We'll know when all of the old Bitcoin P2PK addresses and transacted from addresses are swept.

GrilledChips 10mo ago
the funny thing is that nobody will ever do that. The moment someone uses quantum computing or any other technology to crack bitcoin in a visible way, the coins they just gave to themselves become worthless because confidence collapses.
- pona-a 10mo ago
  There are some Bitcoin puzzles or old wallets that give some plausible deniability.
- Traubenfuchs 10mo ago
  Well, they wouldn't go for the trillion dollar wale addresses. They would hack random, long unused, dead addresses holding 5 figure amounts and slowly convert those to money. They would eventually start to significantly lower the value and eventually crash bitcoin if too greedy, but could get filthy rich.

Traubenfuchs 10mo ago

Cloud providers will love it when we will need to buy more compute and memory for post quantum TSL.

nacozarina 10mo ago

another late signal will be a funding spike 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

cubefox 10mo ago

This sounds slightly alarming: > I’m going to close this post with a warning. When Frisch and Peierls wrote their now-famous memo in March 1940, estimating the mass of Uranium-235 that would be needed for a fission bomb, they didn’t publish it in a journal, but communicated the result through military channels only. As recently as February 1939, Frisch and Meitner had published in Nature their theoretical explanation of recent experiments, showing that the uranium nucleus could fission when bombarded by neutrons. But by 1940, Frisch and Peierls realized that the time for open publication of these matters had passed. > Similarly, at some point, the people doing detailed estimates of how many physical qubits and gates it’ll take to break actually deployed cryptosystems using Shor’s algorithm are going to stop publishing those estimates, if for no other reason than the risk of giving too much information to adversaries. Indeed, for all we know, that point may have been passed already. This is the clearest warning that I can offer in public right now about the urgency of migrating to post-quantum cryptosystems, a process that I’m grateful is already underway. Does anyone know how much underway it is? Do we need to worry that the switch away from RSA won't be broadly deployed before quantum decryption becomes available?

JanisErdmanis 10mo ago
From analytical arguments considering a rather generic error type, we already know that for the Shor algorithm to produce a useful result, the error rate with the number of logical qubits needs to decrease as ~n^(-1/3), where `n` is the number of bits in the number [1]. This estimate, however, assumes that interaction can be turned on between arbitrary two qubits. In practice, we can only do nearest-neighbour interactions on a square lattice, and we need to simulate the interaction between two arbitrary qubits by repeated application of SWAP gates, mangling the interaction through as in the 15th puzzle. This two-qubit simulation would add about `n` SWAP gates, which would then multiply the noise factor by the same factor, hence now we need an error rate for logical qubits on a square lattice to be around ~n^(-4/3) Now comes the error correction. The estimates are somewhat hard to make here, as they depend on the sensitivity of the readout mechanism, but for example let’s say a 10-bit number can be factored with a logical qubit error rate of 10^{-5}. Then we apply a surface code that scales exponentially, reducing the error rate by 10 times with 10 physical qubits, which we could express as ~1/10^{m/10}, where m is the number of physical qubits (which is rather optimistic). Putting in the numbers, it would follow that we need 40 physical qubits for a logical qubit, hence in total 400k physical qubits. That may sound reasonable, but then we made the assumption that while manipulating the individual physical qubits, decoherence for each individual qubit does not happen while they are waiting for their turn. This, in fact, scales poorly with the number of qubits on the chip because physical constraints limit the number of coaxial cables that can be attached, hence multiplexing of control signals and hence the waiting of the qubits is imminent. This waiting is even more pronounced in the quantum computer cluster proposals that tend to surface sometimes. [1]: https://link.springer.com/article/10.1007/s11432-023-3961-3 https://link.springer.com/article/10.1007/s11432-023-3961-3

hellobluelings 10mo ago

[dead]

osn9363739 10mo ago

This is the worst quantum computing will ever be.

AlexandrB 10mo ago
You assume no civilizational collapse is in our future.
- qgin 10mo ago
  Tbh this reply works for pretty much anything anyone ever says
  - osn9363739 10mo ago
    I was attempting a sarcastic jab at the whole "this is the worst AI will ever be". Yet tech (or anything really) will often hit a wall, and be about as good as it's ever going to get.
ktallett 10mo ago
That vastly depends on if we choose to go in the right direction.

noname120 10mo ago

I can’t believe how the very first line of the article is a grotesque strawman. Tbh I expected better from Scott Aaronson.

lukeasrodgers 10mo ago
Could you elaborate as you why you think it is a grotesque strawman? It doesn’t strike me as such, even on rereading.
hiddencost 10mo ago
The guy who spends most of his time posting either in favor of genocide or about how he got cancelled for being a misogynist? He's an excellent scientist but not a calm person.

sallveburrpi 10mo ago

So summary is that useful quantum computing is definitely not imminent (as in probably happening in the next 10-20 years) - or am I misreading ?

ursAxZA 10mo ago

Which one ends up being more accurate — quantum-computing forecasts or fashion-magazine trend predictions?

Antibabelic 10mo ago

Is it possible that practical quantum computing is actually impossible and we only think it is because of our incomplete understanding of physics?

yoan9224 10mo ago

Aaronson's take is characteristically grounded. The Willow chip announcement was impressive technically but the media coverage predictably overshot into "RSA is dead" territory when the actual achievement was improving error correction rates. The relevant timeline question is: when do quantum computers solve problems faster than classical computers for commercially useful tasks (not just contrived benchmarks)? The error correction milestone matters because it's the gate to scaling. Previous quantum systems had error rates that increased faster than you could add qubits, making large-scale quantum computing impossible. If Willow actually demonstrates below-threshold error rates at scale (I'd want independent verification), that unblocks the path to 1000+ logical qubit systems. But we're still probably 5-7 years from "useful quantum advantage" on problems like drug discovery or materials simulation. The economic argument is underrated. Even if quantum computers achieve theoretical advantage, they need to beat rapidly improving classical algorithms running on cheaper hardware. Every year we delay, classical GPUs get faster and quantum algorithms get optimized for near-term noisy hardware. The crossover point might be narrower than people expect. What I find fascinating is the potential for hybrid classical-quantum algorithms where quantum computers handle specific subroutines (like sampling from complex distributions or solving linear algebra problems) while classical computers do pre/post-processing. That's probably the first commercial application - not replacing classical computers entirely but augmenting them for specific bottlenecks. Imagine a drug discovery pipeline where the 3D protein folding simulation runs on quantum hardware but everything else is classical.

OkayPhysicist 10mo ago
First? Try only. I'd be willing to wager a sizeable amount of money that no one save for a few niche research institutions trying to improve quantum computing will ever be using fully quantum setups. QC is not a panacea. There are a handful of algorithms that are in BQP-P, and most of those aren't really used in tasks I would imagine the average person frequently engaging in. Simultaneously, quantum computers necessarily have complications that classical computers lack. Combined, I doubt people will be using purely quantum computers ever.

ProllyInfamous 10mo ago

Vanderbilt University [0] is about to open a "quantum research graduate studies" campus, somewhere near Chattanooga, Tennessee. I have a degree in chemistry from that institution, and don't have a clue what this means beyond the $1,000,000,000 economic impact this facility is supposed to make upon our fair city, over the next decade. [•] <https://quantumzeitgeist.com/vanderbilt-university-quantum-quantum-research/ https://quantumzeitgeist.com/vanderbilt-university-quantum-q...> [0] In partnership with our government-subsidized "commercial quantum-ready" fiber network, EPB