7 ms·

Not trolling, but curious - do quantum computers do anything useful yet?

obi1kenobi 7y ago
There are some interesting ideas around using quantum computers for verifiably-random numbers, including a proposal from Scott Aaronson himself: https://www.quantamagazine.org/how-to-turn-a-quantum-computer-into-the-ultimate-randomness-generator-20190619/ https://www.quantamagazine.org/how-to-turn-a-quantum-compute...
- fsh 7y ago
  I just don't get why you would want to use a quantum computer to generate random numbers. Hardware-RNGs are cheap and have existed for decades. Your CPU probably has one built-in. Some even rely on quantum effects such as shot noise, but where is the advantage over using say thermal noise of a resistor? Both are completely unpredictable.
  - obi1kenobi 7y ago
    If you want random numbers just for yourself, all of the approaches you mention are fine to use. The difference is that by using a quantum computer, one could generate random numbers and convince others that the numbers are actually random and not rigged.
baddox 7y ago
My impression is that we've recent just maybe gotten to the point where someone has proven that they have a computer that actually is doing quantum computing for something that would be exponentially slower to do on a classical computer. My understanding is that this is what Google has recently claimed to have done, and before that no one had published any serious claims that they had done real quantum computing. As always, Scott Aaronson has a solid article, some of which I can understand: https://www.scottaaronson.com/blog/?p=4317 https://www.scottaaronson.com/blog/?p=4317
dekhn 7y ago
No. There have been some interesting quantum simulation papers but nobody has shown anything yet that is revolutionary. This is promising work that may be interesting in the future: https://arxiv.org/pdf/1902.10171.pdf https://arxiv.org/pdf/1902.10171.pdf This also looks like it could be interesting: http://meetings.aps.org/Meeting/MAR20/Session/W17.7 http://meetings.aps.org/Meeting/MAR20/Session/W17.7 (Gurobi is a CPU solver for integer and linear programming problems, which are some of the most useful to solve quickly. There is also: https://ai.googleblog.com/2016/07/towards-exact-quantum-description-of.html https://ai.googleblog.com/2016/07/towards-exact-quantum-desc...
- kaiabwpdjqn 7y ago
  can you give an example of a linear programming task that is not currently practical to solve on classical computers but could become so with a huge speed up?
  - MrK93 7y ago
    Routing, TSP, scheduling, they all benefit from huge speed ups.
    - kaiabwpdjqn 7y ago
      I guess. But we already optimize these things. Without any specific domain in mind, I wonder how much better we could get. Like maybe amazon could find the global minimum cost to route, but right now it’s getting pretty darn close. Or maybe that’s entirely naive and the potential for finding faster solutions to real time problems is huge
      - dekhn 7y ago
        it is huge. that's the only reason people are motivated to implement QC- because in principle then we can break crypto, do QM much faster, solve intractable problems, etc. Day-to-day, we're not really blocked on QC to get important work done.
6nf 7y ago
Almost but not yet
- lisper 7y ago
  Almost? What have they done that you would consider "almost" useful?
  - 6nf 7y ago
    They have proved that it's physically possible for quantum computers to do things that classical computers can not. In other words, they have proved that quantum supremacy is real.
    - lisper 7y ago
      No, they haven't. There is nothing that a QC can do that a CC cannot. CC's are universal. They can compute any computable function. What QC's can do in theory is perform some computations much faster than a CC can. One QC has actually done that, but the computation was of a function that cannot reasonably be called "useful". The potentially useful things that QCs can do is speed up factoring, protein folding analysis, simulation of chemical reactions... no QC has come anywhere near doing any of those things.
      - 6nf 7y ago
        You don’t agree with Google’s November paper then I guess? You KNOW what quantum supremacy means. Please don’t nit pick my layman’s description we are all adults here. You know what I meant.
        lisper 7y ago
        I'm not taking issue with your definition of quantum supremacy, I'm taking issue with your (implied) definition of "almost useful". Personally, I don't consider the demonstration of quantum supremacy in and of itself to be useful. It is very interesting, but IMHO it is not (yet) fair to say that QCs have done anything useful, even if you hedge with "almost".
deleted 7y ago
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klingonopera 7y ago
I have absolutely no clue about quantum computing, but I remember this from two years ago. Haven't heard anything since. Is this relevant? Does anyone have thoughts on this? https://spectrum.ieee.org/tech-talk/telecom/security/china-successfully-demonstrates-quantum-encryption-by-hosting-a-video-call https://spectrum.ieee.org/tech-talk/telecom/security/china-s...
- chrispeel 7y ago
  Quantum encryption as in the IEEE Spectrum article is not the same thing as quantum computing, which is what the original post is about. So no, not relevant Even so, HN is all about the non-relevant stuff, so I'll give my two bits on quantum encryption, which is that it is dramatically easier than quantum computing for short distances, yet even so its not practical to replace our entire internet such as to enable its use. And until the quantum computers are built, there's no need for it
  - dreamcompiler 7y ago
    > And until the quantum computers are built, there's no need for it. Disagree. One of the coolest things about quantum encryption is that any attempt to eavesdrop a communication is instantly detectable. This is extremely useful for communication between conventional computers.
brian-armstrong 7y ago
Sure, they've led to lots of grants and work for grad students.
- kragen 7y ago
  Hi! What do you think the postquantum security story for Bitcoin looks like? That is, if someone starts being able to build big quantum computers, what vulnerabilities does that create in Bitcoin, and is there a way we can solve them in time to keep the whole system from collapsing?
core-questions 7y ago
https://www.dwavesys.com/applications https://www.dwavesys.com/applications is worth looking at, they quote 200 different applications for their system. Truly useful as in profitable, maybe not yet, but it's still early days - it would be like asking Von Neumann how he plans to handle microtransactions
- iainmerrick 7y ago
  From what I’ve read about Von Neumann, he’d probably take a decent stab at answering that!
  - core-questions 7y ago
    Oh, no doubt, and I bet you could get someone from any of the current QC companies to go hog wild with ideas over a beer or two, but in practical reality what matters is execution and manufacturing - something that Honeywell, Google, et. al. have been scant on but seems to be core to what D-Wave is doing.

There are some interesting ideas around using quantum computers for verifiably-random numbers, including a proposal from Scott Aaronson himself: https://www.quantamagazine.org/how-to-turn-a-quantum-computer-into-the-ultimate-randomness-generator-20190619/ https://www.quantamagazine.org/how-to-turn-a-quantum-compute...

fsh 7y ago
I just don't get why you would want to use a quantum computer to generate random numbers. Hardware-RNGs are cheap and have existed for decades. Your CPU probably has one built-in. Some even rely on quantum effects such as shot noise, but where is the advantage over using say thermal noise of a resistor? Both are completely unpredictable.
- obi1kenobi 7y ago
  If you want random numbers just for yourself, all of the approaches you mention are fine to use. The difference is that by using a quantum computer, one could generate random numbers and convince others that the numbers are actually random and not rigged.

baddox 7y ago

My impression is that we've recent just maybe gotten to the point where someone has proven that they have a computer that actually is doing quantum computing for something that would be exponentially slower to do on a classical computer. My understanding is that this is what Google has recently claimed to have done, and before that no one had published any serious claims that they had done real quantum computing. As always, Scott Aaronson has a solid article, some of which I can understand: https://www.scottaaronson.com/blog/?p=4317 https://www.scottaaronson.com/blog/?p=4317

dekhn 7y ago

No. There have been some interesting quantum simulation papers but nobody has shown anything yet that is revolutionary. This is promising work that may be interesting in the future: https://arxiv.org/pdf/1902.10171.pdf https://arxiv.org/pdf/1902.10171.pdf This also looks like it could be interesting: http://meetings.aps.org/Meeting/MAR20/Session/W17.7 http://meetings.aps.org/Meeting/MAR20/Session/W17.7 (Gurobi is a CPU solver for integer and linear programming problems, which are some of the most useful to solve quickly. There is also: https://ai.googleblog.com/2016/07/towards-exact-quantum-description-of.html https://ai.googleblog.com/2016/07/towards-exact-quantum-desc...

kaiabwpdjqn 7y ago
can you give an example of a linear programming task that is not currently practical to solve on classical computers but could become so with a huge speed up?
- MrK93 7y ago
  Routing, TSP, scheduling, they all benefit from huge speed ups.
  - kaiabwpdjqn 7y ago
    I guess. But we already optimize these things. Without any specific domain in mind, I wonder how much better we could get. Like maybe amazon could find the global minimum cost to route, but right now it’s getting pretty darn close. Or maybe that’s entirely naive and the potential for finding faster solutions to real time problems is huge
    - dekhn 7y ago
      it is huge. that's the only reason people are motivated to implement QC- because in principle then we can break crypto, do QM much faster, solve intractable problems, etc. Day-to-day, we're not really blocked on QC to get important work done.

6nf 7y ago

Almost but not yet

lisper 7y ago
Almost? What have they done that you would consider "almost" useful?
- 6nf 7y ago
  They have proved that it's physically possible for quantum computers to do things that classical computers can not. In other words, they have proved that quantum supremacy is real.
  - lisper 7y ago
    No, they haven't. There is nothing that a QC can do that a CC cannot. CC's are universal. They can compute any computable function. What QC's can do in theory is perform some computations much faster than a CC can. One QC has actually done that, but the computation was of a function that cannot reasonably be called "useful". The potentially useful things that QCs can do is speed up factoring, protein folding analysis, simulation of chemical reactions... no QC has come anywhere near doing any of those things.
    - 6nf 7y ago
      You don’t agree with Google’s November paper then I guess? You KNOW what quantum supremacy means. Please don’t nit pick my layman’s description we are all adults here. You know what I meant.
      - lisper 7y ago
        I'm not taking issue with your definition of quantum supremacy, I'm taking issue with your (implied) definition of "almost useful". Personally, I don't consider the demonstration of quantum supremacy in and of itself to be useful. It is very interesting, but IMHO it is not (yet) fair to say that QCs have done anything useful, even if you hedge with "almost".

deleted 7y ago

[deleted]

klingonopera 7y ago

I have absolutely no clue about quantum computing, but I remember this from two years ago. Haven't heard anything since. Is this relevant? Does anyone have thoughts on this? https://spectrum.ieee.org/tech-talk/telecom/security/china-successfully-demonstrates-quantum-encryption-by-hosting-a-video-call https://spectrum.ieee.org/tech-talk/telecom/security/china-s...

chrispeel 7y ago
Quantum encryption as in the IEEE Spectrum article is not the same thing as quantum computing, which is what the original post is about. So no, not relevant Even so, HN is all about the non-relevant stuff, so I'll give my two bits on quantum encryption, which is that it is dramatically easier than quantum computing for short distances, yet even so its not practical to replace our entire internet such as to enable its use. And until the quantum computers are built, there's no need for it
- dreamcompiler 7y ago
  > And until the quantum computers are built, there's no need for it. Disagree. One of the coolest things about quantum encryption is that any attempt to eavesdrop a communication is instantly detectable. This is extremely useful for communication between conventional computers.

brian-armstrong 7y ago

Sure, they've led to lots of grants and work for grad students.

kragen 7y ago
Hi! What do you think the postquantum security story for Bitcoin looks like? That is, if someone starts being able to build big quantum computers, what vulnerabilities does that create in Bitcoin, and is there a way we can solve them in time to keep the whole system from collapsing?

core-questions 7y ago

https://www.dwavesys.com/applications https://www.dwavesys.com/applications is worth looking at, they quote 200 different applications for their system. Truly useful as in profitable, maybe not yet, but it's still early days - it would be like asking Von Neumann how he plans to handle microtransactions

iainmerrick 7y ago
From what I’ve read about Von Neumann, he’d probably take a decent stab at answering that!
- core-questions 7y ago
  Oh, no doubt, and I bet you could get someone from any of the current QC companies to go hog wild with ideas over a beer or two, but in practical reality what matters is execution and manufacturing - something that Honeywell, Google, et. al. have been scant on but seems to be core to what D-Wave is doing.