4 ms·

Which statement are you saying demonstrates why people shouldn't take quantum complexity theory seriously?

scottlocklin 7y ago
BQP doesn't exist: there are no quantum computers. Saying BQP is like saying "magic fairy dust perfect unitary transformers that effectively encode a perfect complex number in the same sense a protractor theoretically can solve NP-complete problems by encoding real numbers."
- daveFNbuck 7y ago
  So we shouldn't take research into things that don't exist yet seriously?
  - scottlocklin 7y ago
    Designing algorithms for a computer architecture that assumes matter behaves in a fairly trivially unphysical way sure seems like a glass bead game to me. Especially considering the hype and baloney around this particular one. There are zero actual quantum computer designs (aka error corrected and capable of factoring large or even small integers into primes) under construction: but everyone runs around like chicken little declaring the sky is falling. I went to a Gordon conference on this subject in the 1990s; as far as I can tell, there has been zero progress in the topic since then. Sure are a lot of press releases though!
    - doubleunplussed 7y ago
      At what odds would you bet that we won't see a quantum computer outperforming a classical computer on any problems in the next, say, 20 years?
- doubleunplussed 7y ago
  The qbits and unitaries don't have to be perfect - it's about how things scale when you add qbits. Quantum error correction shows that you can add more qbits to make up for imperfection, and still be left with a quantum computer, i. e. the imperfection hasn't demoted the thing to a classical computer. Of course they haven't built one yet, but none of the difficulties encountered so far have involved discovering new physics, which is what you would need to do to rule out quantum computers since the laws of physics as currently understood permit them.
  - scottlocklin 7y ago
    You've just regurgitated Aaronson's statement on the topic. Aaronson never studied physics, and has probably never fiddled with an op-amp or tried to make entangled anything in the world of matter. There's zero evidence quantum error correction will work; it's just an idea with no basis in the world of matter. There's zero evidence you can meaningfully and usefully manipulate quantum coherent states, let alone manipulate an exponentially huge number of them with a polynomially large number of computational elements, which is the essential claim of quantum computing. They make great claims: great claims need evidence; not theoretical wankery. Building a couple of scalable error corrected qubits would be a great start; it might even cause me to shut up about it. Never in the history of the human race has something as complex as a computer architecture existed in the theoretical world before it exists in some form in the physical world, let alone one for which we define complexity classes. The entire field is intensely silly, and the last time I said so in a public place, the waiter turned out to be some dude who just got his Ph.D. in the subject. He didn't agree with me exactly, but the fact the dude had a job bringing people steaks for a living is a decent argument I'm right.
    - doubleunplussed 7y ago
      My arguments are my own. I am an atomic physicist, and I meaningfully and usefully manipulate coherent quantum states every day. Not for making a quantum computer mind you, but quantum states nonetheless. Quantum mechanics works. The atoms do exactly what the Schrödinger equation says they should, however much entanglement is added. We are yet to see it break down. Plenty of my colleagues are working on quantum computers, with atoms, ions, photons, and solid state systems, and from where I stand it doesn't look like nonsense. It looks steady progress, and if there are insurmountable barriers, they have not yet been encountered. I am not certain that quantum computers are possible, but I am certain that you are wildly overconfident that they are not.
- nabla9 7y ago
  The problem here is that you just state something that looks like strong personal opinion. You vaguely refer to serious people.

BQP doesn't exist: there are no quantum computers. Saying BQP is like saying "magic fairy dust perfect unitary transformers that effectively encode a perfect complex number in the same sense a protractor theoretically can solve NP-complete problems by encoding real numbers."

daveFNbuck 7y ago
So we shouldn't take research into things that don't exist yet seriously?
- scottlocklin 7y ago
  Designing algorithms for a computer architecture that assumes matter behaves in a fairly trivially unphysical way sure seems like a glass bead game to me. Especially considering the hype and baloney around this particular one. There are zero actual quantum computer designs (aka error corrected and capable of factoring large or even small integers into primes) under construction: but everyone runs around like chicken little declaring the sky is falling. I went to a Gordon conference on this subject in the 1990s; as far as I can tell, there has been zero progress in the topic since then. Sure are a lot of press releases though!
  - doubleunplussed 7y ago
    At what odds would you bet that we won't see a quantum computer outperforming a classical computer on any problems in the next, say, 20 years?
doubleunplussed 7y ago
The qbits and unitaries don't have to be perfect - it's about how things scale when you add qbits. Quantum error correction shows that you can add more qbits to make up for imperfection, and still be left with a quantum computer, i. e. the imperfection hasn't demoted the thing to a classical computer. Of course they haven't built one yet, but none of the difficulties encountered so far have involved discovering new physics, which is what you would need to do to rule out quantum computers since the laws of physics as currently understood permit them.
- scottlocklin 7y ago
  You've just regurgitated Aaronson's statement on the topic. Aaronson never studied physics, and has probably never fiddled with an op-amp or tried to make entangled anything in the world of matter. There's zero evidence quantum error correction will work; it's just an idea with no basis in the world of matter. There's zero evidence you can meaningfully and usefully manipulate quantum coherent states, let alone manipulate an exponentially huge number of them with a polynomially large number of computational elements, which is the essential claim of quantum computing. They make great claims: great claims need evidence; not theoretical wankery. Building a couple of scalable error corrected qubits would be a great start; it might even cause me to shut up about it. Never in the history of the human race has something as complex as a computer architecture existed in the theoretical world before it exists in some form in the physical world, let alone one for which we define complexity classes. The entire field is intensely silly, and the last time I said so in a public place, the waiter turned out to be some dude who just got his Ph.D. in the subject. He didn't agree with me exactly, but the fact the dude had a job bringing people steaks for a living is a decent argument I'm right.
  - doubleunplussed 7y ago
    My arguments are my own. I am an atomic physicist, and I meaningfully and usefully manipulate coherent quantum states every day. Not for making a quantum computer mind you, but quantum states nonetheless. Quantum mechanics works. The atoms do exactly what the Schrödinger equation says they should, however much entanglement is added. We are yet to see it break down. Plenty of my colleagues are working on quantum computers, with atoms, ions, photons, and solid state systems, and from where I stand it doesn't look like nonsense. It looks steady progress, and if there are insurmountable barriers, they have not yet been encountered. I am not certain that quantum computers are possible, but I am certain that you are wildly overconfident that they are not.
nabla9 7y ago
The problem here is that you just state something that looks like strong personal opinion. You vaguely refer to serious people.