3 ms·

> But they don't have stable qubits and so they can't run Shor's algorithm. So D-Wave's machines are similar to AMD's and NVIDIA's I don't see what's "unstable

> But they don't have stable qubits and so they can't run Shor's algorithm. So D-Wave's machines are similar to AMD's and NVIDIA's I don't see what's "unstable" about a D-Wave qubit; it has an input bias and it has biases about the qubits it is connected to, which you can tune, and quantum coherence is held for long enough for there to provably be tunnelling effects involved in the process of settling down to a ground state. I think there's a massive lack of understanding about quantum computing that includes a huge bias against these quantum annealers, and it's baffling to me - why wouldn't someone want to see this process work? Certainly their early customers and developers see something there that you might not. Everyone's obsessed about Shor's algorithm, but it's not the most interesting thing in the world, is it? I mean, do you really want all current encryption to be rendered worthless by whoever owns it? I'm happier to see things go in the direction of solving optimization problems for traffic flow and scheduling instead of military uses, for once.

kragen 7y ago
I don't mean D-Wave's devices are bad. They're just not quantum computers. They might be a better computational architecture than the mainstream ones for something (although, as I understand it, the jury is still out on that). But they can't run the quantum computation algorithms we've developed over the last 35 years, so they aren't "quantum computers" as we've been using the term for 35 years, and they won't have the effects on, for example, cryptography and our understanding of physics, that we've been predicting that "quantum computers" will have. They can't evaluate quantum circuits, they can't solve problems in BQP in polynomial time with the BQP error bound, and the whole simulation question applicable to quantum computers is inapplicable to them. These statements are not errors of reasoning attributable to some bias I might have against quantum annealers; they're just true. Calling them "quantum computers" is therefore unhelpful; it is guaranteed to cause people to draw incorrect inferences. It's like describing a slide rule, an op-amp integrator, or a harmonic analyzer as a "computer", except that that was common usage at one time. "Quantum annealers" is fine. Now, while my comment isn't motivated by any animus against the devices, which indeed might turn out to be useful, I do bear a grudge against the company D-Wave. Specifically, I think they're billing their devices as "quantum computers" precisely because they want people to draw incorrect inferences about them. That is, by using that term, they're intentionally misleading people into thinking their product can do things it can't, in order to get press and investment money. That's a very bad thing to do, and they are bad people. You ask, "I mean, do you really want all current encryption to be rendered worthless by whoever owns it?" There is a substantial field of "postquantum cryptography", with conferences going back 14 years, that will not be demolished by quantum computers. In particular, SHA-256, AES-256, and things based on them will be fine, and even a lot of cryptographic work from the 1970s will be fine if it uses those modern primitives. There are a number of public-key cryptosystems that should also work, but in most cases, we don't yet have the level of confidence in those that we have in the more conservative designs I mentioned above. The exception is Merkle signatures, which have their own disadvantages. I have a second, more disturbing objection to your query about what "I want": you seem to be presupposing that my beliefs about D-Wave, and perhaps everyone's beliefs about everything all the time, are determined exclusively by wishful thinking. Consider, perhaps, that this may not be the case — some of the time people may have beliefs that they would prefer to be incorrect, based on, for example, evidence or careful reasoning. In fact, I would assure you that this is true, but certainly you could dismiss that as more wishful thinking on my part. While it's convenient to attribute people disagreeing with you to "a massive lack of understanding" or to wishful thinking, often it turns out that they instead disagree with you because they know things you don't. Under those circumstances, it can sometimes be more useful to avoid insulting them.
- core-questions 7y ago
  I still don't see how it's at all reasonable to claim that a device which is proven to execute computation using quantum effects is "not a quantum computer". It's "not a quantum gate model computer", sure, but such things are presently vaporware, so why should they get to claim the term? To me you sound like an abacus fan who is waiting for Big Abacus to release an even bigger model, while Turing is labouring away with silly gears and cogs that you see no value in.
  - kragen 7y ago
    As I explained above, we already have a term for "a device which is proven to execute computation using quantum effects"; we call it a "computer". All practical computers (since the transition from vacuum tubes to transistors, and arguably before that) depend on quantum effects for their computation. Transistor action is a quantum-mechanical effect, which is why the Boltzmann constant pops up in the middle of the Ebers–Moll equation. Please do not resort to personal attacks on this site. Your repeated insulting remarks do not rise to the standards of behavior we attempt to maintain here.

kragen 7y ago

I don't mean D-Wave's devices are bad. They're just not quantum computers. They might be a better computational architecture than the mainstream ones for something (although, as I understand it, the jury is still out on that). But they can't run the quantum computation algorithms we've developed over the last 35 years, so they aren't "quantum computers" as we've been using the term for 35 years, and they won't have the effects on, for example, cryptography and our understanding of physics, that we've been predicting that "quantum computers" will have. They can't evaluate quantum circuits, they can't solve problems in BQP in polynomial time with the BQP error bound, and the whole simulation question applicable to quantum computers is inapplicable to them. These statements are not errors of reasoning attributable to some bias I might have against quantum annealers; they're just true. Calling them "quantum computers" is therefore unhelpful; it is guaranteed to cause people to draw incorrect inferences. It's like describing a slide rule, an op-amp integrator, or a harmonic analyzer as a "computer", except that that was common usage at one time. "Quantum annealers" is fine. Now, while my comment isn't motivated by any animus against the devices, which indeed might turn out to be useful, I do bear a grudge against the company D-Wave. Specifically, I think they're billing their devices as "quantum computers" precisely because they want people to draw incorrect inferences about them. That is, by using that term, they're intentionally misleading people into thinking their product can do things it can't, in order to get press and investment money. That's a very bad thing to do, and they are bad people. You ask, "I mean, do you really want all current encryption to be rendered worthless by whoever owns it?" There is a substantial field of "postquantum cryptography", with conferences going back 14 years, that will not be demolished by quantum computers. In particular, SHA-256, AES-256, and things based on them will be fine, and even a lot of cryptographic work from the 1970s will be fine if it uses those modern primitives. There are a number of public-key cryptosystems that should also work, but in most cases, we don't yet have the level of confidence in those that we have in the more conservative designs I mentioned above. The exception is Merkle signatures, which have their own disadvantages. I have a second, more disturbing objection to your query about what "I want": you seem to be presupposing that my beliefs about D-Wave, and perhaps everyone's beliefs about everything all the time, are determined exclusively by wishful thinking. Consider, perhaps, that this may not be the case — some of the time people may have beliefs that they would prefer to be incorrect, based on, for example, evidence or careful reasoning. In fact, I would assure you that this is true, but certainly you could dismiss that as more wishful thinking on my part. While it's convenient to attribute people disagreeing with you to "a massive lack of understanding" or to wishful thinking, often it turns out that they instead disagree with you because they know things you don't. Under those circumstances, it can sometimes be more useful to avoid insulting them.

core-questions 7y ago
I still don't see how it's at all reasonable to claim that a device which is proven to execute computation using quantum effects is "not a quantum computer". It's "not a quantum gate model computer", sure, but such things are presently vaporware, so why should they get to claim the term? To me you sound like an abacus fan who is waiting for Big Abacus to release an even bigger model, while Turing is labouring away with silly gears and cogs that you see no value in.
- kragen 7y ago
  As I explained above, we already have a term for "a device which is proven to execute computation using quantum effects"; we call it a "computer". All practical computers (since the transition from vacuum tubes to transistors, and arguably before that) depend on quantum effects for their computation. Transistor action is a quantum-mechanical effect, which is why the Boltzmann constant pops up in the middle of the Ebers–Moll equation. Please do not resort to personal attacks on this site. Your repeated insulting remarks do not rise to the standards of behavior we attempt to maintain here.