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What are we going to do with quantum computers?
- montrose 9y agoI've always assumed that, however here quantum computers are in labs you can read articles about, they're herer at the NSA. Is there any external evidence that the NSA is already using them?
- HaoZeke 9y agoNone actually. If the NSA or anyone had managed to find a use for the sort of Quantum computers that are floating around the world would be very different. However currently these computers are constrained by classical memory and read write operations are still classical. I'm willing to bet it'll be a century more at this rate before quantum computing comes of age. Since the 40s people have been hyping them without any sort of clear understanding.
- symlinkk 9y agoHow would the world be different? Presumably they’d keep it a secret.
- bartread 9y ago> Since the 40s people have been hyping them without any sort of clear understanding. Groan: it's going to be Cloud/Big Data/ML/Blockchain hype all over again except possibly worse. I don't mind the technology, but the tsunami of vapid content (and conversation) that comes with it wears me out.
- andybak 9y ago> If the NSA or anyone had managed to find a use for the sort of Quantum computers that are floating around the world would be very different. Remember how much effort the British put into making it hard for the Axis to realise that Engima had been cracked. To the extent that they allowed ships to be sunk and sailors to die. If a 3 letter agency does have anything then they are probably hoping to keep that edge for as long as possible. (This doesn't mean that I believe they do - merely that I don't think it would be immediately obvious if they did)
- OscarCunningham 9y agoInformation regularly leaks out of the NSA. It doesn't seem like they'd be able to keep this a secret. It could be that they have some super secret projects which are protected by much better security, but I doubt it. If they could be that competent for one project, why not use the same protocols everywhere?
- spacehome 9y agoThat's what they want you to think.
- mannykannot 9y ago> If they could be that competent for one project, why not use the same protocols everywhere? For exactly the reason set out in the post you are replying to, I would think, at least for a while. Though that approach to security does not always last. The USA almost gave away that it had broken the Japanese navy's most important cyphers through its interception of Admiral Yamamoto.
- OscarCunningham 9y ago>40s This is a typo, surely? Quantum computers were first proposed in the 80s.
- HaoZeke 9y agoYup, sorry, typed that on an alphanumeric. But tech-hype has always existed, side by side with those claiming tech has maxed out... It's disappointing to see the media even try TBH.
- ianai 9y agoI think you’re right: “In 1982, the Nobel prize-winning physicist Richard Feynman thought up the idea of a 'quantum computer', a computer that uses the effects of quantum mechanics to its advantage” https://www.doc.ic.ac.uk/~nd/surprise_97/journal/vol4/spb3/ https://www.doc.ic.ac.uk/~nd/surprise_97/journal/vol4/spb3/
- kensai 9y agoWho is the market leader now? Is it D-Wave or IBM? Someone else?!
- acct1771 9y agoThe Chinese, perhaps.
- stochastic_monk 9y agoD-Wave computers are quantum annealers, not machines capable of running, for example, Grover’s or Shor’s algorithm. And even these algorithms can help asymptotic complexity, but not solve an NP complete problem in polynomial time. (Even AES256 is pretty much safe against a quantum attack, since a quantum computer effectively square roots the time complexity, and that just leaves key-exchange protocols, of which several QR-variants exist.) Personally, I think the hype far outweighs the value, even compared to Big Data/IoT.
- taejo 9y ago> And even these algorithms can help asymptotic complexity Is this a theorem or conjecture?
- stochastic_monk 9y agoExisting quantum algorithms have not yet been found which have reduced NP-complete problems to polynomial time. (See [0] for a pretty comprehensive list.) IE, I was talking about quantum algorithms we have, none of which have done so, not stating the impossibility of such an algorithm. I am not aware of a proof that comments on whether or not such an algorithm is impossible, however. [0]: https://math.nist.gov/quantum/zoo/ https://math.nist.gov/quantum/zoo/
- Torai 9y agoSerious quantum computers ARE FINALLY HERE That would involve both the hardware and software is ready for production and use. So it's my thing or is it MIT Technology Review writers who are misleading common people into thinking quantum computing will be usable in a couple of years?
- andybak 9y agoYes. From my layman's view the fact that there are serious scientists in the field who still doubt that practical quantum computation is even realistically possible surely indicates we're not on the verge of being able to order one for delivery.
- OscarCunningham 9y agoOn the other hand I'm sure you could find lots of other achievements where some scientists were denying it was possible right up to the point it was achieved.
- akvadrako 9y agoThat's missing the point. Until it's actually achieved it isn't "finally here".
- andybak 9y ago"If an elderly but distinguished scientist says that something is possible, he is almost certainly right; but if he says that it is impossible, he is very probably wrong." https://www.brainyquote.com/quotes/arthur_c_clarke_100793 https://www.brainyquote.com/quotes/arthur_c_clarke_100793 > On the other hand I'm sure you could find lots of other achievements where some scientists were denying it was possible right up to the point it was achieved. True and I'm very aware that I'm creeping towards the age where I'm likely to be on the wrong side of these debates. (Not that I'm distinguished or even a scientist) However - the distinguished, elderly scientists are sometimes right.
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- quotemstr 9y agoI wonder whether we'll first use quantum computers to perform cryptanalysis against archived unencrypted traffic. We've conducted ourselves for decades underthe assumption that the cryptographic invariants securing internet communications would hold. Looking to the future, we can switch to quantum-resistant ciphers and go on with our lives. But the past? Mass decryption of archived communication would lead to learning things we never wanted to know. It would cause economic ruin, social turmoil, and worse on a huge scale. And it may now be inevitable. Everyone has secrets. We should start moving toward quantum-resistant cryptography now so that by the time these machines become practical, sensitive information will have fallen out of most archives.
- lawl 9y ago> We should start moving toward quantum-resistant cryptography now so that by the time these machines become practical, sensitive information will have fallen out of most archives. I think we actually are. NIST already gathered submissions for post quantum crypto[0] last year. And people like djb are also clearly interested in it[1][2]. [0] https://csrc.nist.gov/projects/post-quantum-cryptography/round-1-submissions https://csrc.nist.gov/projects/post-quantum-cryptography/rou... [1] https://blog.cr.yp.to/20170719-pqbench.html https://blog.cr.yp.to/20170719-pqbench.html [2] https://sphincs.org/ https://sphincs.org/
- mort96 9y agoI know very little about the topic. Will post-quantum crypto require new hardware? The few techniques I have heard about rely on special networks capable of transmitting quantum particles, not just bits. If new network infrastructure is required, I can't imagine how we would ever get quantum computer resistant cryptography before it's way too late.
- nokcha 9y ago>Will post-quantum crypto require new hardware? No. We just need to switch from existing public-key cryptographic algorithms to quantum-resistant public-key cryptographic algorithms. There are already a variety of such algorithms developed (see https://en.wikipedia.org/wiki/Post-quantum_cryptography https://en.wikipedia.org/wiki/Post-quantum_cryptography). All that remains is to study them further and agree on a standard. Symmetric ciphers such as AES are already quantum-resistant for 256-bit keys. (Grover's algorithm is the best known quantum attack for such algorithms. Cracking an N-bit key classically is approximately as hard as cracking an (N/2)-bit key on a quantum computer with Grover's algorithm.)
- nightcracker 9y agoIs it possible to massively speed up ray tracing by representing geometry in a quantum program and then using superposition to evaluate many ray paths simultaneously? That would be exciting in <N> years for real time accurate ray tracing. This is just a wild guess without much knowledge of quantum computing at all though.
- grondilu 9y agoRay tracing is typically the kind of things you want to do as fast as possible, ideally in real time. Quantum computers will never work fast. Also if I'm not mistaken ray tracing scales well with conventional computers : the quality of your output is proportional to the number of rays you simulate. So it's not an appropriate use case for quantum computers.
- posterboy 9y agobut it's not linear with the number of reflections and transissions, I guess, if you want physically correct materials. Or if you want aberations and, well, "quantum effects" like in the slit experiment.
- nhaehnle 9y agoIn short, no. Quantum computers don't really compute many things in parallel. Or rather, they do, but the problem is getting the results out. To stick with your ray tracing question, you could probably indeed trace an exponentially (in the size of the computer) number of rays, but at the end you have to do go back to the classical world to actually read out data, and you'd essentially be able to only read out the result of one ray picked at random. Quantum computers are only know to provide exponential speedups in cases where there is some algebraic structure to exploit when condensing the exponentially many computations down to a single result. That's why you can get an exponential speedup for factoring or discrete logarithm, but not for symmetric cryptography or really any other useful problem (except for the kind of circular problem of simulating quantum systems). That's what makes me personally hope that quantum computers will never scale. The likely outcome of quantum computing is the worst of all worlds: all known practically useful cryptography will be broken, and practically nothing will really benefit.
- grondilu 9y agoI personally envision quantum computers and machine learning working together to "solve" biology. QC would solve difficult molecular dynamics problems (like protein foldings, enzymatic reactions...) and ML would learn those results to simulate large aggregates of such molecules (like a whole cell or even a whole organism).
- ianai 9y agoFrom how QC is done, that seems unlikely. It seems to me a QC would best model quantum processes but anything larger would require astronomical numbers if qubits.
- recentdarkness 9y agoFinally a viable platform to mine bitcoin and other crypto currencies
- zakk 9y agoYou cannot mine Bitcoin with a quantum computer, as there is no quantum algorithm to calculate SHA hashes.
- tromp 9y agoAll hashcash based PoW, including bitcoin's, is subject to quantum speedup by Grover's search algorithm. It allows you to find a hash output with 80 leading zero bits in roughly 2^40 steps rather than the 2^80 steps classically needed.
- deleted 9y ago[deleted]
- selimthegrim 9y agohttps://twitter.com/preskill/status/966088602659667968 https://twitter.com/preskill/status/966088602659667968
- mesozoic 9y agoBitcoin mining mostly
- fiatjaf 9y agoThere must be a way to explain the principle behind quantum computers for a layman that understands both computers and quantum mechanics. Where is that explanation?
- anonytrary 9y agoThis is a tall order considering physicists haven't really come up with a layman explanation for the latter. The best way to understand quantum mechanics is to do the math, taking the Copenhagen interpretation to be true. Sadly, this is the only way to gain an intuition for quantum mechanics.
- Kequc 9y agoThe government is going to use them to finally start decrypting all of the VPN traffic they've been storing all these years.
- YeGoblynQueenne 9y ago>> Not just any computer, but one on the verge of passing what may, perhaps, go down as one of the most important milestones in the history of the field. Well, I don't know enough about quantum computers to be able to tell what's going on here, but "on the verge" and "finally here" sound a bit contradictory. Are we expecting to have useful quantum computers soon, like the article's opening paragraph suggests, or do we already have them, as the title does?
- TekMol 9y agoI never got really far explaining myself what a quantum computer is. From what I understand, this is what we can do with a quantum bit: class Qbit { var $p; function randomize($p) { $this->p=$p; } function observe() { if ( $this->p > random() ) $this->p=1; else $this->p=0; return $this->p; } } The interesting things probably get possible when you have multiple qbits. Not just a normal array of qbits, but qbits that have some kind of interaction (entanglement?). Would it be possible to simulate 'multiqbits' in a piece of code similarly small as the one above?
- ikeboy 9y agohttps://www.scottaaronson.com/democritus/lec10.html https://www.scottaaronson.com/democritus/lec10.html Here's a start.
- TekMol 9y agoThank you. But I don't think in formulas. I think in code.
- ianai 9y agoIgnore the equations and read the words. From a quick look, they have some customized notation but also heuristically valid descriptions.
- Thimothy 9y agohttps://www.smbc-comics.com/comic/the-talk-3 https://www.smbc-comics.com/comic/the-talk-3 I like this one better.
- ikeboy 9y agoYou can poke around https://quantumexperience.ng.bluemix.net/qx/experience https://quantumexperience.ng.bluemix.net/qx/experience and see if there's anything helpful
- deleted 9y ago[deleted]
- Asdfbla 9y agoHow long does a computation step in a quantum computer (which I guess is technically a measurement) actually take? I'm (at a superficial level) aware of Grover's and Shor's algorithms, but only in the sense that they provide asymptotic speedups in the number of steps required for the computation. In classical computers it's easy to envision some model where a step is just some constant number of cycles or whatever, but how long do the measurements take in quantum computers? I guess it depends on the specific experimental setup of your quantum computer somehow, but I'm just curious about the real-world speeds. A hypothetical computer that does few steps but takes a minute for each measurement wouldn't be so useful.
- mirekrusin 9y agoSingle measurement collapses to some fixed state. You need to reset the whole thing and do measurement again. Repeat it many times and you'll start seeing distribution that you're interested in. Your solution/algo will amplify correct answers. Single measurement is like revealing single pixel of a picture. If you do it enough times, you know what's on the picture.
- PeterisP 9y agoYeah, so the question is about the order of magnitude it takes for each such simple measurement; how much time does it take to reset the whole thing and do measurement again - how many times per second/hour/whatever can we hope do do that.
- mcguire 9y agoAnd how many times do you need to do it to get the precision you want?
- greeneggs 9y agoIt depends on the implementation. Ion traps are slower than superconducting qubits, for example, although they are speeding up. This paper, from 2014, gives some parameters: "Logic gates at the surface code threshold: Superconducting qubits poised for fault-tolerant quantum computing" Campbell et al. Nature, 2014 https://arxiv.org/abs/1402.4848 https://arxiv.org/abs/1402.4848 From page 9: Initialization ~50ns Measurement ~200ns One-qubit gates ~20ns Two-qubit gates ~40ns
- Digit-Al 9y agoAnyone know how you'd debug a quantum algorithm? It doesn't look like it would be possible to step through the code in a debugger.
- vpribish 9y agoyou can simulate it in a regular computer and debug there.
- erikj 9y agoI thought "serious" meant at least one million error-corrected qubits or so, and it seems to me that we're at least two decades away from this. The article is talking about the 50 qubits milestone without proper error correction.
- neltnerb 9y agoWhy do you think so many qubits would be needed in order for it to be serious? The article quotes quantum computer researchers as saying 50-100 qubits could perform computations that are intractable on any classical computer. I'm inclined to believe them, the state space grows way faster than linearly as you entangle more particles.
- Strilanc 9y agoTo encode 100 logical error-corrected qubits, you need on the order of 100K to 1M physical qubits. People mix up the two types all the time.
- efangs 9y agoIt's true that at 50-100 physical (not logical) qubits, it's no longer possible to simulate classically. That does not mean that they are useful. As other people pointed out, you may need a factor of 100-1000 more physical qubits to get as many logical qubits.
- samirm 9y agowhat a clickbait title
- intrasight 9y agoAs was mentioned in the article, applications in chemical and physical simulation seem very promising. I would think that error correction would not be an issue. You would use QC to identify possible solutions which could then be verified by traditional computers.