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Quantum computers ready to leap out of the lab in 2017

171 points by seycombi 10y ago

basicplus2 10y ago
What would have to happen to change the current thinking to believe that quantum computing is not possible?
- hannob 10y ago
  I don't think that's what most people familiar with the topic believe. It's just considered to be very hard (and some think it's so hard that it may be practically impossible for a very long time).
- adrianN 10y ago
  Somebody finding that quantum computers can solve NP-hard problems would be very suspicious. Other than that it would need someone to find a flaw with quantum mechanics.
  - Meegul 10y ago
    It was to my understanding that some NP-complete problems - like factorization - are (theoretically) solvable in P time using quantum computing, all within (and indeed as a result of) the constraints of quantum mechanics, perhaps utilizing Shor's algorithm. And that this fact does not imply P=NP, but rather that we'd have a computer that could perform some exponential functions as if some logarithm were applied to them. I'm no expert, but at the very least I believe it's recognized that some subset of NP problems, perhaps not NP-hard, should be solvable as if they were polynomial, using quantum computers. That said, my knowledge of this subject starts and ends with things I've read on the internet, so I could be mistaken. Either way, this[1] was a very interesting introduction to some of the implications/concepts that are involved with this. 1: http://www.scottaaronson.com/papers/philos.pdf http://www.scottaaronson.com/papers/philos.pdf
    - Ar-Curunir 10y ago
      Factorisation is very, very, very unlikely to be NP-complete. P is a separate class from the class of problems considered efficiently solvable; BQP is the class of problems that are efficiently solved by quantum computers, and it is believed that BQP is strictly larger than P.
      - Meegul 10y ago
        Ah alright. Looks like I have some more reading to do this morning.
  - kleiba 10y ago
    Somebody finding that quantum computers can solve NP-hard problems [efficiently] would be very suspicious. The missing word here is "efficiently": all problems in NP are solvable.
- marcosdumay 10y ago
  Are you aware that there are many quantum computers working in labs around the world, right?
  - basicplus2 10y ago
    My question does not mean I don't believe in quantum computers
pmiller2 10y ago
Interesting that there's not even a mention of D-Wave here.
- doppioandante 10y ago
  I have been told that D-Wave is not actually a quantum computer but a quantum annealer, but I don't know the difference.
  - sigmaprimus 10y ago
    I have also heard that it is not a true Quantum computer although it solves the ising problem faster than simulated annealING systems and it also uses qBits (>1024 atm) and I believe both Google and UCLA own or at least use Dwave systems. So if it looks like a duck and quacks like a duck.... Anyways nice article even if it did not mention Dwave. The Hacker News community comments section can take care of that!!
    - kurthr 10y ago
      They really aren't all that similar, and it only solves a tiny subset of Ising problems (which match D-Wave topology), and they really aren't faster than a single modern Intel core running a reasonable algorithm. http://www.scottaaronson.com/blog/?p=2555 http://www.scottaaronson.com/blog/?p=2555
    - marcosdumay 10y ago
      It can not factorize numbers in polynomial time, it can not speed-up chemical simulations, it can do basically nothing that a quantum computer does, besides simulating itself. It's also not obvious in any way what use there is in simulating quantum annealing.
      - kobeya 10y ago
        Search. You can use quantum annealing for unstructured search.
guardian5x 10y ago
Does anyone know if Apple actively works at Quantum Computing?
- mike-cardwell 10y ago
  I'd be surprised. They don't do anything similar. What Apple essentially does is: Plug computer parts together, wrap in a shiny case, add software.
  - WhitneyLand 10y ago
    This way off base. They have dedicated scientific research labs. This is just one example them giving a peek: http://www.businessinsider.com/apple-published-first-artificial-intelligence-research-paper-2016-12 http://www.businessinsider.com/apple-published-first-artific...
    - Ar-Curunir 10y ago
      This is the first research paper they've published; they do not have a strong research presence precisely because they did not allow publication of research carried out at Apple, making it difficult to hire researchers whose career depends on said publications. Furthermore, AI is very different from the fundamental research underlying quantum computing.
      - pdabbadabba 10y ago
        Yes. But GP was simply refuting the assertion that all Apple does is "Plug computer parts together, wrap in a shiny case, add software," not claiming that Apple has a strong research presence or is working on a quantum computer.
        Ar-Curunir 10y ago
        To me saying that they have "dedicated research labs" is at least partially claiming that they have strong research presence.
mathgenius 10y ago
"Quantum computing has long seemed like one of those technologies that are 20 years away, and always will be." I've just completed a PhD in this area, and I've never heard this sentiment before. It seems quite unlike fusion research, which is famously always 50 years (?) away. Quantum computing research is proceeding at a rapid pace, and actually it is perhaps only 20 years old in total. Although Feynman considered something akin to a quantum computer in the 80's, it really wasn't until the 90's that quantum error correction became a thing. So it really is a very young field of research. The "old-timers", they are all about 40 years old now, unlike other areas of physics where the oldies really are very old!
- Ar-Curunir 10y ago
  I agree with your comment, but just a small nitpick: Peter Shor and Umesh Vazirani are probably much older than 40 :P
  - mathgenius 10y ago
    Yeah let me add to your list: John Preskill, Alex Kitaev, Reinhard Werner... But these guys transferred sideways to (aka. invented parts of) quantum computing.
- ridgeguy 10y ago
  Congrats on your PhD. Can you suggest any review articles for those of us who would like an overview of the current state of the art? Thanks!
- Xcelerate 10y ago
  I've just completed my PhD as well. My research was all computational and consisted mainly of molecular dynamics simulations and machine learning. However, I did a lot of quantum chemistry work (QMC, DFT) as well and have taken QM classes — quantum mechanics, quantum field theory, density functional theory. Any other knowledge that would be relevant for quantum computing I've learned on my own (Nielsen and Chuang, etc.) I'd really like to work for one of the quantum computing companies (Rigetti, etc.) or research groups (QuAIL), but I'm not really sure how to proceed in applying to these places given that my background isn't exactly quantum computing research. Since you have experience in this area, would you have any tips on how to apply to one of these groups? My current line of thought is to just apply directly via their websites, and if I don't hear anything back, begin contributing to the relevant Github quantum computing projects as proof of capability. Would you have any suggestions for a better approach?
ThePhysicist 10y ago
I was not aware of Rob Schoelkopf's initiative so far (http://quantumcircuits.com/ http://quantumcircuits.com/), I think this could be serious competition for John Martinis & Google. From their website it seems that they use a 3D cavity approach to quantum computing, which is (or at least was) pursued by IBM as well. Here, instead of using superconducting resonators on a chip, you use superconducting 3-dimensional cavity resonators (typically made from Aluminium) in which you place "naked" qubits that are fabricated on a Sapphire substrate. The advantage of this is that the attainable quality factor of the cavity is much higher than for a coplanar waveguide resonator (although those resonators have caught up quite a bit thanks to work that was done e.g. by the Martinis lab), and that there are fewer noise sources around the qubits. Personally my current bet would be on Martinis or Schoelkopf to win the race, as they have the best access to both funding (though I don't know the funding details of QuantumCircuits) and Academic resources. Most of the original work on Transmon-based qubits was done at the Schoelkopf lab, and it seems that he has excellent technicians on his team. In general though it still seems more probable that a ion-based quantum computer will be the first "real" quantum computer, as the technology is more mature and (for small numbers of qubits at least) easier to scale. Exciting times!
- mtgx 10y ago
  I wonder if anyone is pursuing Andrea Morello [1] and his team's silicon-based quantum chip idea, which they've also said has much better stability than superconducting qubits: https://newsroom.unsw.edu.au/news/science-tech/quantum-computer-coding-silicon-now-possible https://newsroom.unsw.edu.au/news/science-tech/quantum-compu... https://newsroom.unsw.edu.au/news/science-tech/quantum-computers-10-fold-boost-stability-achieved https://newsroom.unsw.edu.au/news/science-tech/quantum-compu... I'd much rather ultimately see silicon-based quantum computers, which may eventually become advanced (streamlined) enough to be used by mainstream users, too. Quantum computers using superconductors and liquid nitrogen will never become mainstream. They would just be used by corporations and governments. So I hope there will be more investing in silicon-based quantum computing research sooner rather than later. Or if not silicon, at least another material that could one day become as cheap and practical. EDIT: As for who will be the "first" with a practical quantum computer, it does seem like Google will be the one to release a 50-qubit computer this year or the next [2]. There are like 10 other companies that have built 5-qubit quantum computers, but that was still mainly a science experiment to prove that a quantum computer can be made at all. A 50-qubit quantum computer would establish a new threshold and according to Martinis [3], at least, it should be easier to scale from that point forward. In other words, the "quantum era" may actually begin then. I imagine those "stuck" at 5-qubits still have a long way to go before they can scale quickly beyond that. [1] http://www.theaustralian.com.au/higher-education/new-spin-on-silicon-implants-wins-global-recognition/news-story/75b2fc7e399e58921d7d5c8e09d93f03 http://www.theaustralian.com.au/higher-education/new-spin-on... [2] https://www.technologyreview.com/s/602283/googles-quantum-dream-may-be-just-around-the-corner/ https://www.technologyreview.com/s/602283/googles-quantum-dr... [3] https://www.wired.com/2014/09/martinis/ https://www.wired.com/2014/09/martinis/
saycheese 10y ago
Putting aside speed, what is possible in quantum computing that's not possible in classical computing?
- xapata 10y ago
  Some problems can be solved immediately, in a single clock cycle, that are intractable for a traditional CPU. For example, cracking RSA encryption.
  - ctz 10y ago
    This is not even remotely close to being true. Shor's algorithm runs in polynomial time.
  - jMyles 10y ago
    > single clock cycle What does this even mean in this context? My understanding (which is limited!) is that there are some apparently NP-complete problems that are P for a quantum process. Now, it may be that these problems were never actually NP-complete, but are a superset of P for quantum computers. Or it may be that quantum computers can really solve some NP-complete problems in P time. Either way though, it isn't a consequence of CPU-cycles per se, but the underlying mathematical distinction (ie, what a silicon vs quantum computer does, not what it can do in a "cycle").
    - Ar-Curunir 10y ago
      If quantum computers could solve NP-complete problems efficiently, the entire community would astounded. As it stands, quantum computers can solve some problems faster than classical computers currently can; factorisation, discrete log and other problems with a particular kind of repeated structure are some such problems. However, we do not know for certain that these problems are not efficiently solvable using classical computers (I'd bet that factorisation will be put in P within my lifetime). A big goal of the QC community is to demonstrate quantum supremacy: to unconditionally show that quantum computers can solve a problem with fewer resources than classical computers. We've made progress on this (check out Scott Aaronson's blog for more info), but still haven't achieved it. Lastly, a small nitpick. "P time" is not a meaningful phrase; P is a complexity class consisting of problems solvable efficiently (i.e., in polynomial time) on classical computers. The class of efficiently solvable problems on quantum computers is BQP: Bounded-error Quantum Polynomial-time, which means that BQP is the class of problems that are efficiently solved by a quantum computer, but only with some probability bounded away from 1/2. This means the QC can return incorrect answers, but there are techniques to reduce the error probability to extremely small values. The classical analogue of this class is BPP, which is Bounded-error probabilistic poly-time. There's a conjecture that BPP=P, and if we have any sort of crypto then the conjecture is true.
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ivan_ah 10y ago
Anyone interested in learning quantum mechanics should first learn/review their linear algebra. Understanding quantum states and quantum measurements is really not that complicated once you're comfortable with vectors and matrices. Shameless plug: I wrote a linear algebra book that discusses applications to quantum mechanics, including quantum computing. Check out an extended preview here: https://minireference.com/static/excerpts/noBSguide2LA_preview.pdf#page=143 https://minireference.com/static/excerpts/noBSguide2LA_previ... Available electronically here https://gum.co/noBSLA https://gum.co/noBSLA and the print version is coming soon.
- GFK_of_xmaspast 10y ago
  See also Lipton&Regan: https://mitpress.mit.edu/books/quantum-algorithms-linear-algebra https://mitpress.mit.edu/books/quantum-algorithms-linear-alg...
- mathgenius 10y ago
  That's so boring! I recommend people learn whatever they want, and then if needed go and read a maths book. Much more fun that way. (Btw, I don't mean to dis your book, it looks good to me.) Edit: just to elaborate on this. I hear often from people "what math do i need to learn so i can do X?" And I just think that alot of the time people should just do X and this will force them to figure out the math as needed. Learning math from a book is brutally difficult! Just like learning a programming language, what is the best way to do that? You start with a project that you want to do. People who want to read the "pre-requisite book" often-times just seem to be deferring the real crunch that happens when you actually get down to the business of actually learning X.
  - Ar-Curunir 10y ago
    I can understand your approach. It helps to learn a topic (like linear algebra) when you can immediately see it's applications. However, I'm not sure it would work here; for one, quantum mechanics is not an "easily" understood application, like, say PCA, or DFT, or other such things.
  - groovy2shoes 10y ago
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orblivion 10y ago
How soon before PGP archive backups are no longer secure? (And everyone's old backups are retroactively made insecure)?
- mtgx 10y ago
  > It is estimated that 2048-bit RSA keys could be broken on a quantum computer comprising 4,000 qubits and 100 million gates. Experts speculate that quantum computers of this size may be available within the next 20-30 years. https://security.stackexchange.com/questions/87345/how-many-qubits-are-needed-to-factor-2048-bit-rsa-keys-on-a-quantum-computer https://security.stackexchange.com/questions/87345/how-many-... I think it's possible we'll have a 4,000 qubit quantum computer by 2030 if a 50-qubit one is released this year, and if quantum computers can also follow a "Moore's Law" of sorts. At least D-Wave seems to be doing it - from 28-qubits in 2007 to 2,000 in 2017. https://en.wikipedia.org/wiki/D-Wave_Systems https://en.wikipedia.org/wiki/D-Wave_Systems I imagine the NSA/Russia/China would be interested in decrypting communications of at least some people even 15 years after they happened, and they could find some use for them. We already know they intend to store encrypted data indefinitely and they just add new storage for the newly obtained data rather than overwriting the old one.
  - Ar-Curunir 10y ago
    D-Wave computers are not general quantum computers; they can perform only a limited set of computations.
  - orblivion 10y ago
    Glad I use 4096 bit keys, heh. On that note though, exactly how much encrypted data do they intend to store? You could probably thwart it by sending tons and tons of noise for a small signal. Do they have more storage than Amazon? This stuff isn't free.
jackfoxy 10y ago
Anyone know how big a number you can factor with 32 and with 64 qbits? Those qbit goals were a tangible thing that jumped out at me when I scanned the article.
- sgt101 10y ago
  Depends what you mean by qbit. If you are including a magic state factory in your architecture then lots and lots (millions). If you mean stable qbits then I've been told that 4096 bit numbers could be factored with 8000 qbits that are very stable and can be operated on frequently.
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bajskastarn 10y ago
They are not Turing complete, thus no computers at all. 'Quantum computer' is an oxymoron.
- Ar-Curunir 10y ago
  Quantum computaters can do whatever classical computers can (and no more; they're just hypothesized to be more efficient for certain problems).
  - kobeya 10y ago
    This isn't really true. Quantum computation devices are not general-purpose computing chips, like the way an x86 or ARM core is. They are constructed to solve specific instances of specific categories of problems in a way that is more efficient than a classical computer. And you can't accelerate all forms of computation in this way either -- only some very special categories of problems. A "quantum computer" is more likely to look like a CPU/GPU combo where a general-purpose classical chip does the work of arranging work units for a special-purpose quantum accelerator, and interpreting the results.
    - Ar-Curunir 10y ago
      I am not talking about the physical realisation, but rather the theoretical model of computation. How quantum computers are deployed in the real world is irrelevant to the theoretical study...
      - kobeya 10y ago
        I'm not making that distinction either. Quantum computation by its very nature requires special-purpose constructions. There is no such thing as a "general computation" quantum computer. Conceivably there could be a reprogrammable quantum computer able to be reconfigured to handle many different types of computation, but that would be more analogous to an FPGA than a general-purpose CPU.
TheAceOfHearts 10y ago
As I'm completely unfamiliar with the subject, I'm having a hard time wrapping my head around what kind of impact a big development in quantum computing would have. From what I read in the Wikipedia article, it can destroy a lot of our existing crypto, and I can guess at the consequences of this. Taking a very long-term timeline into consideration, would it be speculated that quantum computers would ultimately replace traditional computers? Are there categories of problems for which it would be worse to use a quantum computer?
- kobeya 10y ago
  http://www.smbc-comics.com/comic/the-talk-3 http://www.smbc-comics.com/comic/the-talk-3
  - alexilliamson 10y ago
    That felt informative. Was it... informative??
    - edanm 10y ago
      It was co-authored by a fairly famous researcher in the field (Scott Aaronson), so yes.
    - kobeya 10y ago
      You might enjoy the blog of the guy who co-wrote the script for the comic, himself a prominent quantum computer researcher: http://www.scottaaronson.com/blog/ http://www.scottaaronson.com/blog/
      - alexilliamson 10y ago
        This is great thank you. I'm a super-novice, but extremely fascinated by this field. I just ordered his book Quantum Computing since Democritus.
- mabbo 10y ago
  A friend of mine worked on adiabatic quantum computers at D-Wave for a few years. My understanding (which may be incorrect) is that the speedups are things like take 2^n algorithms and make them 2^(sqrt(n)) instead. It's still exponential, but it's a huge improvement when n hits 100. Will these replace traditional computers? Probably not. But you can bet there will eventually be cloud services that you submit very hard jobs and it spits back an answer faster than any traditional computer could.
verandaguy 10y ago
I'm cautiously optimistic, but I get the impression that this is another one of those "date('Y') + 1 will be the year Linux goes mainstream on desktops" situations. Quantum computers have come leaps and bounds in the past few years. Especially impressive is research into improving the signal-to-noise ratio of qubits through "dressing" them in microwaves[0]. Despite this, quantum computers still aren't, in the overwhelming majority of cases, better at solving problems than classical machines. Some work still needs to be done in terms of getting better signal-to-noise in qubits, as well as in terms of getting more performant hardware in the processors themselves. And before there can be an industry built around quantum computers, there'll likely need to be some new way of keeping quantum processors running without having to keep them in a fridge at near-absolute zero. Again, though, I'm hopeful that QC starts becoming more mainstream soon. [0] https://arxiv.org/pdf/1603.04800v1.pdf

171 points by seycombi 10y ago

basicplus2 10y ago

What would have to happen to change the current thinking to believe that quantum computing is not possible?

hannob 10y ago
I don't think that's what most people familiar with the topic believe. It's just considered to be very hard (and some think it's so hard that it may be practically impossible for a very long time).
adrianN 10y ago
Somebody finding that quantum computers can solve NP-hard problems would be very suspicious. Other than that it would need someone to find a flaw with quantum mechanics.
- Meegul 10y ago
  It was to my understanding that some NP-complete problems - like factorization - are (theoretically) solvable in P time using quantum computing, all within (and indeed as a result of) the constraints of quantum mechanics, perhaps utilizing Shor's algorithm. And that this fact does not imply P=NP, but rather that we'd have a computer that could perform some exponential functions as if some logarithm were applied to them. I'm no expert, but at the very least I believe it's recognized that some subset of NP problems, perhaps not NP-hard, should be solvable as if they were polynomial, using quantum computers. That said, my knowledge of this subject starts and ends with things I've read on the internet, so I could be mistaken. Either way, this[1] was a very interesting introduction to some of the implications/concepts that are involved with this. 1: http://www.scottaaronson.com/papers/philos.pdf http://www.scottaaronson.com/papers/philos.pdf
  - Ar-Curunir 10y ago
    Factorisation is very, very, very unlikely to be NP-complete. P is a separate class from the class of problems considered efficiently solvable; BQP is the class of problems that are efficiently solved by quantum computers, and it is believed that BQP is strictly larger than P.
    - Meegul 10y ago
      Ah alright. Looks like I have some more reading to do this morning.
- kleiba 10y ago
  Somebody finding that quantum computers can solve NP-hard problems [efficiently] would be very suspicious. The missing word here is "efficiently": all problems in NP are solvable.
marcosdumay 10y ago
Are you aware that there are many quantum computers working in labs around the world, right?
- basicplus2 10y ago
  My question does not mean I don't believe in quantum computers

pmiller2 10y ago

Interesting that there's not even a mention of D-Wave here.

doppioandante 10y ago
I have been told that D-Wave is not actually a quantum computer but a quantum annealer, but I don't know the difference.
- sigmaprimus 10y ago
  I have also heard that it is not a true Quantum computer although it solves the ising problem faster than simulated annealING systems and it also uses qBits (>1024 atm) and I believe both Google and UCLA own or at least use Dwave systems. So if it looks like a duck and quacks like a duck.... Anyways nice article even if it did not mention Dwave. The Hacker News community comments section can take care of that!!
  - kurthr 10y ago
    They really aren't all that similar, and it only solves a tiny subset of Ising problems (which match D-Wave topology), and they really aren't faster than a single modern Intel core running a reasonable algorithm. http://www.scottaaronson.com/blog/?p=2555 http://www.scottaaronson.com/blog/?p=2555
  - marcosdumay 10y ago
    It can not factorize numbers in polynomial time, it can not speed-up chemical simulations, it can do basically nothing that a quantum computer does, besides simulating itself. It's also not obvious in any way what use there is in simulating quantum annealing.
    - kobeya 10y ago
      Search. You can use quantum annealing for unstructured search.

guardian5x 10y ago

Does anyone know if Apple actively works at Quantum Computing?

mike-cardwell 10y ago
I'd be surprised. They don't do anything similar. What Apple essentially does is: Plug computer parts together, wrap in a shiny case, add software.
- WhitneyLand 10y ago
  This way off base. They have dedicated scientific research labs. This is just one example them giving a peek: http://www.businessinsider.com/apple-published-first-artificial-intelligence-research-paper-2016-12 http://www.businessinsider.com/apple-published-first-artific...
  - Ar-Curunir 10y ago
    This is the first research paper they've published; they do not have a strong research presence precisely because they did not allow publication of research carried out at Apple, making it difficult to hire researchers whose career depends on said publications. Furthermore, AI is very different from the fundamental research underlying quantum computing.
    - pdabbadabba 10y ago
      Yes. But GP was simply refuting the assertion that all Apple does is "Plug computer parts together, wrap in a shiny case, add software," not claiming that Apple has a strong research presence or is working on a quantum computer.
      - Ar-Curunir 10y ago
        To me saying that they have "dedicated research labs" is at least partially claiming that they have strong research presence.

mathgenius 10y ago

"Quantum computing has long seemed like one of those technologies that are 20 years away, and always will be." I've just completed a PhD in this area, and I've never heard this sentiment before. It seems quite unlike fusion research, which is famously always 50 years (?) away. Quantum computing research is proceeding at a rapid pace, and actually it is perhaps only 20 years old in total. Although Feynman considered something akin to a quantum computer in the 80's, it really wasn't until the 90's that quantum error correction became a thing. So it really is a very young field of research. The "old-timers", they are all about 40 years old now, unlike other areas of physics where the oldies really are very old!

Ar-Curunir 10y ago
I agree with your comment, but just a small nitpick: Peter Shor and Umesh Vazirani are probably much older than 40 :P
- mathgenius 10y ago
  Yeah let me add to your list: John Preskill, Alex Kitaev, Reinhard Werner... But these guys transferred sideways to (aka. invented parts of) quantum computing.
ridgeguy 10y ago
Congrats on your PhD. Can you suggest any review articles for those of us who would like an overview of the current state of the art? Thanks!
Xcelerate 10y ago
I've just completed my PhD as well. My research was all computational and consisted mainly of molecular dynamics simulations and machine learning. However, I did a lot of quantum chemistry work (QMC, DFT) as well and have taken QM classes — quantum mechanics, quantum field theory, density functional theory. Any other knowledge that would be relevant for quantum computing I've learned on my own (Nielsen and Chuang, etc.) I'd really like to work for one of the quantum computing companies (Rigetti, etc.) or research groups (QuAIL), but I'm not really sure how to proceed in applying to these places given that my background isn't exactly quantum computing research. Since you have experience in this area, would you have any tips on how to apply to one of these groups? My current line of thought is to just apply directly via their websites, and if I don't hear anything back, begin contributing to the relevant Github quantum computing projects as proof of capability. Would you have any suggestions for a better approach?

ThePhysicist 10y ago

I was not aware of Rob Schoelkopf's initiative so far (http://quantumcircuits.com/ http://quantumcircuits.com/), I think this could be serious competition for John Martinis & Google. From their website it seems that they use a 3D cavity approach to quantum computing, which is (or at least was) pursued by IBM as well. Here, instead of using superconducting resonators on a chip, you use superconducting 3-dimensional cavity resonators (typically made from Aluminium) in which you place "naked" qubits that are fabricated on a Sapphire substrate. The advantage of this is that the attainable quality factor of the cavity is much higher than for a coplanar waveguide resonator (although those resonators have caught up quite a bit thanks to work that was done e.g. by the Martinis lab), and that there are fewer noise sources around the qubits. Personally my current bet would be on Martinis or Schoelkopf to win the race, as they have the best access to both funding (though I don't know the funding details of QuantumCircuits) and Academic resources. Most of the original work on Transmon-based qubits was done at the Schoelkopf lab, and it seems that he has excellent technicians on his team. In general though it still seems more probable that a ion-based quantum computer will be the first "real" quantum computer, as the technology is more mature and (for small numbers of qubits at least) easier to scale. Exciting times!

mtgx 10y ago
I wonder if anyone is pursuing Andrea Morello [1] and his team's silicon-based quantum chip idea, which they've also said has much better stability than superconducting qubits: https://newsroom.unsw.edu.au/news/science-tech/quantum-computer-coding-silicon-now-possible https://newsroom.unsw.edu.au/news/science-tech/quantum-compu... https://newsroom.unsw.edu.au/news/science-tech/quantum-computers-10-fold-boost-stability-achieved https://newsroom.unsw.edu.au/news/science-tech/quantum-compu... I'd much rather ultimately see silicon-based quantum computers, which may eventually become advanced (streamlined) enough to be used by mainstream users, too. Quantum computers using superconductors and liquid nitrogen will never become mainstream. They would just be used by corporations and governments. So I hope there will be more investing in silicon-based quantum computing research sooner rather than later. Or if not silicon, at least another material that could one day become as cheap and practical. EDIT: As for who will be the "first" with a practical quantum computer, it does seem like Google will be the one to release a 50-qubit computer this year or the next [2]. There are like 10 other companies that have built 5-qubit quantum computers, but that was still mainly a science experiment to prove that a quantum computer can be made at all. A 50-qubit quantum computer would establish a new threshold and according to Martinis [3], at least, it should be easier to scale from that point forward. In other words, the "quantum era" may actually begin then. I imagine those "stuck" at 5-qubits still have a long way to go before they can scale quickly beyond that. [1] http://www.theaustralian.com.au/higher-education/new-spin-on-silicon-implants-wins-global-recognition/news-story/75b2fc7e399e58921d7d5c8e09d93f03 http://www.theaustralian.com.au/higher-education/new-spin-on... [2] https://www.technologyreview.com/s/602283/googles-quantum-dream-may-be-just-around-the-corner/ https://www.technologyreview.com/s/602283/googles-quantum-dr... [3] https://www.wired.com/2014/09/martinis/ https://www.wired.com/2014/09/martinis/

saycheese 10y ago

Putting aside speed, what is possible in quantum computing that's not possible in classical computing?

xapata 10y ago
Some problems can be solved immediately, in a single clock cycle, that are intractable for a traditional CPU. For example, cracking RSA encryption.
- ctz 10y ago
  This is not even remotely close to being true. Shor's algorithm runs in polynomial time.
- jMyles 10y ago
  > single clock cycle What does this even mean in this context? My understanding (which is limited!) is that there are some apparently NP-complete problems that are P for a quantum process. Now, it may be that these problems were never actually NP-complete, but are a superset of P for quantum computers. Or it may be that quantum computers can really solve some NP-complete problems in P time. Either way though, it isn't a consequence of CPU-cycles per se, but the underlying mathematical distinction (ie, what a silicon vs quantum computer does, not what it can do in a "cycle").
  - Ar-Curunir 10y ago
    If quantum computers could solve NP-complete problems efficiently, the entire community would astounded. As it stands, quantum computers can solve some problems faster than classical computers currently can; factorisation, discrete log and other problems with a particular kind of repeated structure are some such problems. However, we do not know for certain that these problems are not efficiently solvable using classical computers (I'd bet that factorisation will be put in P within my lifetime). A big goal of the QC community is to demonstrate quantum supremacy: to unconditionally show that quantum computers can solve a problem with fewer resources than classical computers. We've made progress on this (check out Scott Aaronson's blog for more info), but still haven't achieved it. Lastly, a small nitpick. "P time" is not a meaningful phrase; P is a complexity class consisting of problems solvable efficiently (i.e., in polynomial time) on classical computers. The class of efficiently solvable problems on quantum computers is BQP: Bounded-error Quantum Polynomial-time, which means that BQP is the class of problems that are efficiently solved by a quantum computer, but only with some probability bounded away from 1/2. This means the QC can return incorrect answers, but there are techniques to reduce the error probability to extremely small values. The classical analogue of this class is BPP, which is Bounded-error probabilistic poly-time. There's a conjecture that BPP=P, and if we have any sort of crypto then the conjecture is true.

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ivan_ah 10y ago

Anyone interested in learning quantum mechanics should first learn/review their linear algebra. Understanding quantum states and quantum measurements is really not that complicated once you're comfortable with vectors and matrices. Shameless plug: I wrote a linear algebra book that discusses applications to quantum mechanics, including quantum computing. Check out an extended preview here: https://minireference.com/static/excerpts/noBSguide2LA_preview.pdf#page=143 https://minireference.com/static/excerpts/noBSguide2LA_previ... Available electronically here https://gum.co/noBSLA https://gum.co/noBSLA and the print version is coming soon.

GFK_of_xmaspast 10y ago
See also Lipton&Regan: https://mitpress.mit.edu/books/quantum-algorithms-linear-algebra https://mitpress.mit.edu/books/quantum-algorithms-linear-alg...
mathgenius 10y ago
That's so boring! I recommend people learn whatever they want, and then if needed go and read a maths book. Much more fun that way. (Btw, I don't mean to dis your book, it looks good to me.) Edit: just to elaborate on this. I hear often from people "what math do i need to learn so i can do X?" And I just think that alot of the time people should just do X and this will force them to figure out the math as needed. Learning math from a book is brutally difficult! Just like learning a programming language, what is the best way to do that? You start with a project that you want to do. People who want to read the "pre-requisite book" often-times just seem to be deferring the real crunch that happens when you actually get down to the business of actually learning X.
- Ar-Curunir 10y ago
  I can understand your approach. It helps to learn a topic (like linear algebra) when you can immediately see it's applications. However, I'm not sure it would work here; for one, quantum mechanics is not an "easily" understood application, like, say PCA, or DFT, or other such things.
- groovy2shoes 10y ago

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orblivion 10y ago

How soon before PGP archive backups are no longer secure? (And everyone's old backups are retroactively made insecure)?

mtgx 10y ago
> It is estimated that 2048-bit RSA keys could be broken on a quantum computer comprising 4,000 qubits and 100 million gates. Experts speculate that quantum computers of this size may be available within the next 20-30 years. https://security.stackexchange.com/questions/87345/how-many-qubits-are-needed-to-factor-2048-bit-rsa-keys-on-a-quantum-computer https://security.stackexchange.com/questions/87345/how-many-... I think it's possible we'll have a 4,000 qubit quantum computer by 2030 if a 50-qubit one is released this year, and if quantum computers can also follow a "Moore's Law" of sorts. At least D-Wave seems to be doing it - from 28-qubits in 2007 to 2,000 in 2017. https://en.wikipedia.org/wiki/D-Wave_Systems https://en.wikipedia.org/wiki/D-Wave_Systems I imagine the NSA/Russia/China would be interested in decrypting communications of at least some people even 15 years after they happened, and they could find some use for them. We already know they intend to store encrypted data indefinitely and they just add new storage for the newly obtained data rather than overwriting the old one.
- Ar-Curunir 10y ago
  D-Wave computers are not general quantum computers; they can perform only a limited set of computations.
- orblivion 10y ago
  Glad I use 4096 bit keys, heh. On that note though, exactly how much encrypted data do they intend to store? You could probably thwart it by sending tons and tons of noise for a small signal. Do they have more storage than Amazon? This stuff isn't free.

jackfoxy 10y ago

Anyone know how big a number you can factor with 32 and with 64 qbits? Those qbit goals were a tangible thing that jumped out at me when I scanned the article.

sgt101 10y ago
Depends what you mean by qbit. If you are including a magic state factory in your architecture then lots and lots (millions). If you mean stable qbits then I've been told that 4096 bit numbers could be factored with 8000 qbits that are very stable and can be operated on frequently.

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bajskastarn 10y ago

They are not Turing complete, thus no computers at all. 'Quantum computer' is an oxymoron.

Ar-Curunir 10y ago
Quantum computaters can do whatever classical computers can (and no more; they're just hypothesized to be more efficient for certain problems).
- kobeya 10y ago
  This isn't really true. Quantum computation devices are not general-purpose computing chips, like the way an x86 or ARM core is. They are constructed to solve specific instances of specific categories of problems in a way that is more efficient than a classical computer. And you can't accelerate all forms of computation in this way either -- only some very special categories of problems. A "quantum computer" is more likely to look like a CPU/GPU combo where a general-purpose classical chip does the work of arranging work units for a special-purpose quantum accelerator, and interpreting the results.
  - Ar-Curunir 10y ago
    I am not talking about the physical realisation, but rather the theoretical model of computation. How quantum computers are deployed in the real world is irrelevant to the theoretical study...
    - kobeya 10y ago
      I'm not making that distinction either. Quantum computation by its very nature requires special-purpose constructions. There is no such thing as a "general computation" quantum computer. Conceivably there could be a reprogrammable quantum computer able to be reconfigured to handle many different types of computation, but that would be more analogous to an FPGA than a general-purpose CPU.

TheAceOfHearts 10y ago

As I'm completely unfamiliar with the subject, I'm having a hard time wrapping my head around what kind of impact a big development in quantum computing would have. From what I read in the Wikipedia article, it can destroy a lot of our existing crypto, and I can guess at the consequences of this. Taking a very long-term timeline into consideration, would it be speculated that quantum computers would ultimately replace traditional computers? Are there categories of problems for which it would be worse to use a quantum computer?

kobeya 10y ago
http://www.smbc-comics.com/comic/the-talk-3 http://www.smbc-comics.com/comic/the-talk-3
- alexilliamson 10y ago
  That felt informative. Was it... informative??
  - edanm 10y ago
    It was co-authored by a fairly famous researcher in the field (Scott Aaronson), so yes.
  - kobeya 10y ago
    You might enjoy the blog of the guy who co-wrote the script for the comic, himself a prominent quantum computer researcher: http://www.scottaaronson.com/blog/ http://www.scottaaronson.com/blog/
    - alexilliamson 10y ago
      This is great thank you. I'm a super-novice, but extremely fascinated by this field. I just ordered his book Quantum Computing since Democritus.
mabbo 10y ago
A friend of mine worked on adiabatic quantum computers at D-Wave for a few years. My understanding (which may be incorrect) is that the speedups are things like take 2^n algorithms and make them 2^(sqrt(n)) instead. It's still exponential, but it's a huge improvement when n hits 100. Will these replace traditional computers? Probably not. But you can bet there will eventually be cloud services that you submit very hard jobs and it spits back an answer faster than any traditional computer could.

verandaguy 10y ago

I'm cautiously optimistic, but I get the impression that this is another one of those "date('Y') + 1 will be the year Linux goes mainstream on desktops" situations. Quantum computers have come leaps and bounds in the past few years. Especially impressive is research into improving the signal-to-noise ratio of qubits through "dressing" them in microwaves[0]. Despite this, quantum computers still aren't, in the overwhelming majority of cases, better at solving problems than classical machines. Some work still needs to be done in terms of getting better signal-to-noise in qubits, as well as in terms of getting more performant hardware in the processors themselves. And before there can be an industry built around quantum computers, there'll likely need to be some new way of keeping quantum processors running without having to keep them in a fridge at near-absolute zero. Again, though, I'm hopeful that QC starts becoming more mainstream soon. [0] https://arxiv.org/pdf/1603.04800v1.pdf