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Quantum computing's reality check
- coffeebeqn 3y agoI was recently learning about Shors Algorithm which was kind of mind blowing until I found out it can’t actually be executed on anything right now. We’re still in the super early days. Like where microcomputers were 40-50 years ago
- ghaff 3y agoLast I looked expert consensus on factoring RSA-2048 was about 15-20 years out but with a wide divergence of opinion. You might find a less optimistic take today,
- bawolff 3y agoI was under the impression the 20 year prediction was for classical methods not quantum
- ghaff 3y agoI can't speak to classical methods but, yes, that was the quantum prediction in report a couple years back.
- oldgradstudent 3y agoAn expert consensus is an interesting social phenomena that should be definitely investigated by anthropologists of science. It tells us nothing about reality.
- tippytippytango 3y agoI'd say we need to go back further, quantum is in the era of the Babbage difference engine.
- Strilanc 3y agoRelated: "Quantum computing worst case scenario: we are Lovelace and Babbage" [1] For scale: Babbage's planned analytical engine had a word size of 50 digits, a clock rate of 7Hz, and a physical size of roughly a locomotive [2]. Contrast [3] where it's estimated that 600-digit superposed additions would run at 27Hz (by dedicating millions of qubits to magic state distillation of the underlying AND gates). Given current plans, a quantum computer capable of doing arithmetic operations as wide and as fast as the analytical engine would probably be larger than the analytical engine. We can see how to do reliable quantum computation in principle. The overhead of error correction makes it daunting in scale. It sure would be nice if someone came along and invented the quantum computing equivalent of a vacuum tube or a transistor. [1]: https://csferrie.medium.com/quantum-computing-worst-case-scenario-we-are-lovelace-and-babbage-1e3005d677e6 https://csferrie.medium.com/quantum-computing-worst-case-sce... [2]: https://medium.com/tech-is-a-tool/building-the-modern-computer-babbages-analytical-engine-8179dedb08c8 https://medium.com/tech-is-a-tool/building-the-modern-comput... [3] "How to factor 2048 bit RSA integers in 8 hours using 20 million noisy qubits" https://quantum-journal.org/papers/q-2021-04-15-433/ https://quantum-journal.org/papers/q-2021-04-15-433/
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- oneshtein 3y agoFirst micro-processor MP944 (1970) had 5360 transistors. (73k transistors with memory). Quantum computer with just 1123 qubits released this month. However, it doesn't work properly yet, because large systems doesn't work as quantum systems, so error rate is high. Large quantum computer is like Eniac at earthquake.
- delusional 3y ago> We’re still in the super early days. Like where microcomputers were 40-50 years ago There's a trap in that sort of thinking. It assumes that it's inevitable that we will at some point arrive at current day for quantum computers. That technology is a straight path in whatever direction we set out. I don't think that is a given. There a plenty of things out there that physics just can't do. Things that, no matter how much effort and thought and research we put into it, we just can't make the world do in a scalable affordable fashion. I don't have the knowledge to make a believable claim that quantum computers are one of those, but you have to consider that it might be. It's possible that quantum computers aren't at the stage of the 8086, but rather at the stage of the flying cars in jetsons. Doomed to forever be an unrealistic dream.
- bena 3y agoYou're right, it is not a given. Progress only looks like a straight shot in hindsight. Yes, we can take any invention today and trace every step back to the previous to make a single unbroken chain to the invention of the wheel. But for every airplane, there's a Bored Ape Yacht Club NFT.
- qmaybe 3y agoThe roadmap of IONQ has them producing 64 logical qubits with error correction within 2025. Whether or not they succeed, I think time will tell as theyve stopped publishing and a cofounder stepped down to return to teaching and research. Quantinuum, the Honeywell merger, expects billions of revenue in 2026. Honeywell gave up on transmons and joined up with their $260m investment into Cambridge. Speaking of transmons, Rigetti is facing delisting IBM is still going hard on transmons and selling mainly to universities. Google had sycamore but were still waiting to see if they’ve solved the cascading errors inherent to scaling Microsoft invested heavily in majorna fermions for compute — which might not even exist. They are not an authority on the physics
- klyrs 3y agoWhat does "expects billions of revenue" mean, precisely?
- qmaybe 3y agoIt means that they are willing to claim to the public that there is a business case for their technology providing billions in value in that year. They do not have the bookings.
- klyrs 3y agoThat's just execs tossing out big numbers about a market they don't understand. They do that all the time. Like babies, they cannot help but fill diapers. That doesn't mean we need to discuss it at the water cooler. Do they have hardware? Is it available? How many nines? Do they have a useful software stack? Does it give developers meaningful leverage to solve problems? The most incredible thing about quantum hype is that ordinarily detail-focused engineer types are getting snowed and buying it because the punchline is too good to be true. But sometimes, these companies make testable claims: if we'd only talk about the externally verifiable ones, and leave the vapor out of it, I think it would make for a much more interesting conversation.
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- dr_dshiv 3y agoOne of the big challenges is being able to frame real world concrete problems in terms that are solvable by quantum algorithms. There are a shocking lack of examples out there. Even when the hardware is there, it isn’t clear how quantum computing can do useful things. But I suspect this is a solvable problem of good communications. But right now, experts in quantum don’t seem to be able to provide these examples. Or they don’t exist.
- reikonomusha 3y agoThis is a good reference: https://quantumalgorithmzoo.org/ https://quantumalgorithmzoo.org/
- dr_dshiv 3y agoDo you see any examples of real world problems in there? Mostly, it is very abstract. This creates a problem, if it is unclear how to use quantum computing to address real world information processing problems
- reikonomusha 3y agoI think this is partly an exercise in defining what "real world" means. To many, solving number theory problems, especially factorization, is real world enough. It's just not Silicon Valley monetizable.
- fxj 3y agoThe big unsolved problem in QC is the lifetime of the QC itself until decoherence. Imagine a computer where you can execute a maximum of 1800 commands (IBM Heron) and then it is broken. That is the status of QC at the moment. A QC might store TB of data and do searches with O(1), but there is no way (at the moment) to upload a TB database to the QC. What we need is a quantum processor that lives for hours or days in a coherent state, but what we have is milli seconds. Just my 2 ct. edit: IBMs Roadmap shows a QC with 1 Billion commands (gates) after 2033. With that machine they could (in principle) upload a 100MB database and do searches. source: https://www.tomshardware.com/tech-industry/quantum-computing/ibm-demonstrates-useful-quantum-computing-within-133-qubit-heron-announces-entry-into-quantum-centric-supercomputing-era https://www.tomshardware.com/tech-industry/quantum-computing...
- red75prime 3y ago> do searches with O(1) Nope. Grover's algorithm allows only O(sqrt(n)) search.
- reikonomusha 3y agoIt's not a big mystery how this will get accomplished however, which is why participants in the field seem hopeful (if modest and tempered). The theory of quantum error correction is rich and pretty well developed. It's just that engineering a system which has enough runway to be error corrected requires a lot of development and innovations in a lot of directions: qubit design and fabrication, quantum compilers, rapid experimental procedures, etc. Edit to edit: Thinking of gate depths as permitting such-and-such megabyte databases as being "uploaded" isn't really a good or accurate metric in my opinion.
- fxj 3y agoWhat puzzles me with IBMs roadmap is their scaling: 2025 156 qubits, 5000 gates 2028 156 qubits, 15K gates 2029 200 qubits, 100M gates 2033 2000 qubits, 1B gates The jump from 15K to 100M gates looks fishy to me. Maybe I am wrong but I doubt that will work that way.
- bawolff 3y agoI don't think its just skeptics. Afaik most researchers (other than those who are trying to attract investments) have been very clear that we are still a ways off from practical quantum computing, and even then the applications of QC is limited to specific domains.
- reikonomusha 3y agoI agree with this. Unimaginable hype was mostly from those with an obvious incentive to raise money, to put themselves on a shortlist for a Nobel, and all that. Most of the ground-floor researchers and experimentalists have been extraordinarily realistic, though sometimes passive or quiet since there's an incentive to not bite the hand that feeds them. It also doesn't help that the giant PR machines of IBM, Google, IonQ, et al. have been commanding the narrative. At this point you'd think transmons, ions, and atoms are the only commercially/at-scale interesting options. :)
- refulgentis 3y ago> Unimaginable hype was mostly from those with an obvious incentive to raise money, to put themselves on a shortlist for a Nobel, and all that Like who? I think we're making up a person.
- reikonomusha 3y agoFor instance, Peter Chapman, among many others. Some of the hype is generated in a quasi-faceless fashion, such as the disaster of a Nature [1] paper by Google, and the surrounding PR claiming they constructed a wormhole with a quantum computer. Or how about Leo Kouwenhoven [2], supported by Microsoft's quantum group, and the retracted Nature papers after their hand was forced? Witness any number of talks at past Q2B conferences to see the audacious claims in applications (healthcare, logistics, ...), chip improvements, etc. [1] "Nature" is a prestigious journal that is a prime target for quantum groups to publish in and consequently milk for PR. [2] https://www.wired.com/story/microsoft-retracts-disputed-quantum-computing-paper/ https://www.wired.com/story/microsoft-retracts-disputed-quan...
- meltyness 3y agoSkepticism of digital computing was a pretty open-air phenomena too. Specialization and generalization of hardware is also cyclical same as centralized and decentralized services.
- YouWhy 3y agoI'm yet to see a single business case of money entering the QC value chain outside of (a) other QC businesses and (b) moonshot investments. After ~15 years of literally the world's smartest people trying to come up with exactly that (some of which are dear friends), the only way conscionable way I can regard QC is as a vapor bubble.
- pclmulqdq 3y agoQuantum computing may be the "cold fusion" of the 2000's. In 2000, it was a fantastic looking technology that looked like it was going to leapfrog classical computing in a whole lot of ways. Now, classical computing has gotten so fast that (for example) O(sqrt(n)) searching of an in-memory structure is just not that exciting - O(n) is totally fine with a 100 GB dataset for many cases, and loading your database into your quantum computer would be O(n) anyway. Ideas for quantum machine learning have been supplanted by LLMs, and Ising optimization machines have already failed in the free market compared to a lot of classical computers. The remaining problems of interest are quantum simulation and encryption cracking, both of which are relatively niche markets.
- daxfohl 3y agoIf the encryption cracking market gets off the ground, would a quantum encryption hardening market come into existence, or can classical encryption algorithms suffice?
- adrian_b 3y agoThere would be only minimal impact of quantum computers over the bulk encryption algorithms (i.e. the 128-bit keys used today when speed is prioritized over security would become deprecated). Where changes would be needed is in digital signatures and certificates and in the key exchange algorithms for the establishment of communication connections in the public Internet, where pre-shared secret keys are not used. Many algorithms have been studied, but they are significantly less efficient than those used today.
- bjornsing 3y agoEver since I understood how quantum computers actually work, I’ve been a skeptic.
- quickthrower2 3y agoFeels like me with Bitcoin. I discovered it “early” but got out off as it sounded too complex for what it did. That wisdom probably cost me millions lol! Actually probably I would have lost the drive as so many did!
- NanoYohaneTSU 3y agoIt won't work. It's just another tech scam that will fail, but at least we got great research out of it.
- reikonomusha 3y agoIf you mean quantum computers can't fundamentally work: you can publish a peer-reviewed paper about why it wouldn't work and the field would be immensely interested.
- pclmulqdq 3y agoGenerally, fields of academic study are not interested in accepting publications on why their field is unnecessary, even when you come at them with evidence.
- l33tman 3y agoWhat the OP suggested was that "it is a scam". It clearly isn't, there is nothing in QC that isn't traditional QM which is a 100 year old incredibly well-tested theory. As far as we currently know, it's an engineering problem, not a question of "will it work". If there is evidence to the contrary, I'm sure any journal would be happy to publish it (that would make it to Science or Nature, not a quantum-computing specific journal).
- klyrs 3y agoGil Kalai has some well-researched opinions along these lines, and he seems to have a mutually respectful relationship with Aaronson.
- resource0x 3y agoThere are plenty of articles explaining why quantum computers won't scale. https://spectrum.ieee.org/the-case-against-quantum-computing https://spectrum.ieee.org/the-case-against-quantum-computing https://www.quantamagazine.org/the-argument-against-quantum-computers-20180207/ https://www.quantamagazine.org/the-argument-against-quantum-... (You can find more by googling)
- seiferteric 3y agoMoore's law was enabled by lithography which enabled a pretty clear path forward on how to shrink transistors over time. AFAIK there is no similar enabling technology for qubit. Maybe that will change, but until then, I don't really see much hope for quantum computers future.
- cma 3y agoYou only need a linear increase in number of error-corrected qubits to get exponential gains on the limited subset of problems they can improve, whereas Moore's law has provided an exponential increase in the number of elements for classical computers. So, Moore's law isn't needed for something similar to Moore's law gains in quantum computing, a linear Moore's law will do if quantum error correction doesn't face scaling laws for the whole ensemble. That might mean they only keep pace with classical computing if Moore's law continues to hold there, but eventually that hits the Landauer limit without new physics (or possibly reversible computing).
- adgjlsfhk1 3y agoIMO this is very wrong. Most real applications of quantum computers will need thousands of error correct qbits (aka millions of real qbits). At the current growth rate in qbits of <100 qbits per year, if the growth was linear, it would be about 10000 years before we had quantum computers solving real problems.
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- kevindamm 3y agoI get the impression that cavity-QED is a similar path for QC that lithography was for classical compute. But I'm not at all an expert, just a curious and interested observer.
- citizenpaul 3y agoI got curious about quantum computers so I ordered and read (most of) Quantum Computation and Quantum Information: 10th Anniversary Edition. It pretty much proved to me that quantum computing is at best 100+ years away or at worst a pipe dream fantasy. Until decoherence at scale is solved there is no way quantum computing will be useful beyond current computing abilities. There is not even a hint that this problem will be solved anytime soon.
- reikonomusha 3y agoExcept published research demonstrates continual improvements in coherence time and implementations of error correction protocols. So "not even a hint" is at best hyperbolic or at worst just wrong.
- echelon 3y agoI felt this way about AI in college. And yet here we are.
- echelon 3y agoTo expand on this - I went into my first AI class in college thinking it'd be amazing. I left with a very bland taste, having solved n-queens a bunch of different ways and written genetic algorithms to "evolve" images. I read Kurzweil before this. I had thought we were decades away from digital immortality. Taking the AI course and algorithm analysis was quite disappointing. Reality set in. Things are harder than we hand wave away. I then started taking bio, read papers on neuroscientists decoding visual signals from mammalian LGN, and went deep down the biology rabbit hole. That only further convinced me that Kurzweil was wishfully wrong. Here are systems more complex than anything previously described to me in my entire life. But now we're confronted with a pace of innovation that is frankly quite humbling. Things I had written off no longer seem impossible. I'm intensely excited for the future.
- Vervious 3y agoI don’t see how you can read and understood Nielsen and Chuang in one sitting, unless you are already a quantum computation theorist. I also don’t see how reading what is essentially an algorithms textbook can lead you to develop an informed opinion about the state of quantum computer engineering… it’s like reading saying “I was curious about how computer software works so I ordered and read CLRS and I don’t think faster computers are anywhere on the horizon in 100 years…”
- odyssey7 3y agoLike Bletchley Park during the last world war, the best-case scenario for intelligence is that the government has quantum computers that break public-key encryption and nobody finds out. It’s hard to know what machines exist behind the scenes.
- brcmthrowaway 3y agoPrescient article: https://scottlocklin.wordpress.com/2019/01/15/quantum-computing-as-a-field-is-obvious-bullshit/ https://scottlocklin.wordpress.com/2019/01/15/quantum-comput...
- kromem 3y agoGeneral purpose QC isn't going to happen all that soon, and may always be faced with scaling issues. But we will see QC in a very specific application before the decade is out. It's kind of a perfect marriage between ML and QC. If you want stochastic outputs and aren't going to know what's going on at each step in the network anyways, the issues of error correction around measurement aren't nearly as crippling as they are for general purpose QC. While initially the work will be converting from classical to optoelectronic hardware for matching current operations, such as MIT's work this year, once we've seen greater availability of optoelectronic hardware I suspect we'll see algorithms for ML developed that would only work in photonic networks and fully exploit the quantum properties therein.
- B1FF_PSUVM 3y ago> If you want stochastic outputs and aren't going to know what's going on at each step in the network anyways You have a way with words, I'm already more at ease with the perspective of a schizophrenic AGI ...
- kromem 3y agoIt's not really any different from the current state of models, it's just that moving the same constraints to a different hardware foundation opens up significant performance gains.
- eigenket 3y agoI am a researcher in quantum information and this seems highly unlikely to me. Quantum computers, as far as I can tell, get significant improvements over classical computers only for quite specific highly mathematically structured problems like the discrete log problem or simulating other quantum systems. I don't think it's likely that there will be substantial "quantum adantage" in the machine learning/ai area.
- itsacomment 3y agoDon't greyed out comments mean someone is downvoting you? What's going on in this thread, this is the second comment of yours that's factually far better than the preceding one but greyed out. I agree with you, quantum ai has only ever been people shouting "quantum" at black box neural nets, as if that had ever produced a viable algorithm yet...
- osigurdson 3y agoThe fact that a working quantum computer exists and works at all is mind blowing to me.
- throwawaysugar 3y agoIt exists for some value of "computer"
- geijoenr 3y agoWhat is happening with QC is very sad. Research on this topic should be a long term scientific endeavor, like nuclear fusion has been for many years. Not the circus it has been so far.
- idkdotcom 3y ago[dead]
- fastneutron 3y agoFor all the people saying this is a scam/waste of money/always 10 years away, I’m curious what you envision the funding model for this kind of speculative tech to be. The government ceased to be the bankroll for this kind of stuff since the end of the Cold War, and for better or for worse, VC is where the money is right now. The marketing BS with stuff like quantum, fusion, carbon capture, etc. is simply a cost of doing business in this environment. If it’s such a travesty that VCs are making bets on tech like this, how then do you fund long term R&D projects with a high risk of failure? Isn’t that the point?
- seydor 3y agothere is general public funding for all kinds of science, including physics I never got the intense interest in quantum computing. My pet theory is that (CS-educated) rich VCs were taken by the word 'computing' , but in reality QC is a theoretical sub-branch of quantum physics. I should test my theory by publishing my tomato computing theory.
- fastneutron 3y agoAnything being done in the public sector (e.g. academia or government) is pocket change by comparison, and so bound up with red tape these days that most truly high risk/reward bets are passed over. That, and you’re at the mercy of congressional budget cycles and the usual grant writing hunger games. If innovation emerges from that environment, it’s in spite of it, not because of it. If private capital wants to fund deeptech, more power to them. If they want forego due diligence and fund tomato computers, that’s (literally) their business.
- dboreham 3y agoExcept Physics might be a branch of CS.
- dekhn 3y agoThe US government has been funding this for quite some time after the cold war and continues to do so. National labs in the US are on the forefront of quantum research (in general) and quantum computing research.
- dmcq2 3y agoI'm pretty certain the QC development will continue even if at a slightly slower rate. And maybe AI can help with manufacturing more reliable and cheap versions :-) What I think has not be investigated so much is what can be done with a not so reliable quantum computer? At the start of computers Colossus was not ultra reliable but that didn't matter as it just cycled around trying different possibilitied on codes so failing on the task every so often wouldn't have made much difference.
- orenlindsey 3y agoQuantum computing is definitely overhyped right now. In my eyes, I don't see how this fundementally changes computing. AI, for example, literally lets you do things that weren't possible before. This just lets you store more data and manipulate it faster. It's not a shift in the core framework of the technology.
- stephc_int13 3y agoFool’s gold. QC is the Alchemy of our times. Just like room-temperature superconductivity is the perpetual motion of our time…
- miika 3y agoCan some explain me, since I don’t know, but I have this idea that ideally quantum computer is like artificial neural network hardware which can change its connections in realtime. I just cannot help seeing how cubits are very much like probabilities comes out from ML, something between 0..1. I’m I completely lost here? I’m curious to understand better:) PS. Is it possible that brain is organic quantum computer? Also. Do you see it possible that our senses and awareness are “prompting” the models we have built during life and thoughts are what comes back from the prompts?
- justinpombrio 3y agoPretty lost yeah, but you're asking questions which is better than 90% of the people who are lost. Some very brief answers: They're called qubits; a cubit is a length about 50cm. Pronounced the same though. Quantum computers are not about being able to change connections in real time. We know how powerful such a computer could be (it can be simulated by a classical computer in polynomial time), and quantum computers are more powerful than that. (Some nitpicker is going to swoop by and say that technically we haven't proven that BQP != P, but if BQP==P then quantum computers are useless anyways.) Quantum amplitudes are not just probabilities: they can be imaginary, and they can be negative. You can add up two non-zero amplitudes and get 0, which is very much not how probabilities work. You can't have a non-zero probability that A happens and a non-zero probability that B happens but a zero probability that A OR B happens, yet with quantum mechanics you get exactly that. Whatever intuition you have for how quantum computers works, it's wrong. Plenty of people have considered that the brain is doing quantum computations. It seems unlikely because the brain is large, wet, and hot, and quantum mechanical systems really like to decohere under those circumstances (breaking the computation). But Roger Penrose still thinks they are. The main takeaway I'd like to convey is that quantum computers are vastly better than classical computers for a few very specialized tasks like taking discrete logarithms and factoring, and no better than classical computers for most everything else. (Vastly better meaning exponentially better: it takes a classical computer with roughly 2^1000 bits of memory to simulate a quantum computer with 1000 bits of memory.)
- quickthrower2 3y agoQuantum winter? Maybe OpenQuantum will do some amazing stuff off a Google paper in 20 years time?
- hackandthink 3y agoQuantum Computers: A Brief Assessment of Progress in the Past Decade https://gilkalai.wordpress.com/2022/05/26/waging-war-on-quantum/ https://gilkalai.wordpress.com/2022/05/26/waging-war-on-quan...