4 ms·

It's true that there is a distinction between a quantum computer build using a universal set of gates(what you probably mean), and one that uses the adiabatic m

It's true that there is a distinction between a quantum computer build using a universal set of gates(what you probably mean), and one that uses the adiabatic model to carry out computations. The former, is difficult to construct due to decoherence, while the latter carries out computations in the ground state, neatly sidestepping the issue. Saying the D-wave computer is not a quantum computer simply because it does not use a universal set of gates is patently false, it uses a different, more restricted model true, but one that still exploits the resources of the quantum realm to carry out computations. It's also true that theoretically, the adiabatic model is less developed, and thus supremacy arguments are more difficult to make, but as long as quantum effects(i.e. superposition, entanglement, etc) are used to carry out computations, it is a quantum computer. > The last time I checked (which was a few years ago) A lot has changed.

whyever 9y ago
> A lot has changed. Could you please give some examples?
kamilner 9y ago
The D-Wave machine is not a full adiabatic quantum computer, though (which would be polynomially equivalent to a universal quantum computer). It does quantum annealing over a pretty restricted set of Hamiltonians. I think it is perfectly reasonable to say it is not a quantum computer, in the same way that not everything performing computation is called a computer. Otherwise---taken to the absurd---why not call a chemist's beaker a quantum computer?
- mabbo 9y ago
  It's a computing machine taking advantage of certain quantum effects to do computing. Theoretically, it may be able to do certain tasks faster than a traditional computer I'm not saying you're wrong- it's often mislabeled as a quantum computer- but it isn't fair to say it's no better than a chemist's beaker.
  - deepnotderp 9y ago
    I guess the problem is that the general public doesn't really know the distinction between quantum annealing and universal quantum computation.
    - hexane360 9y ago
      So maybe articles should include something like: "The D-Wave system uses quantum annealing, which utilizes quantum effects to solve a select few problems much faster than traditional computers. However, it's not as flexible as a universal quantum computer, which could solve a much wider range of problems, including the prime-factorization problem at the heart of modern cryptography."
      - codekilla 9y ago
        I think this is a pretty good summary for an article.
      - deepnotderp 9y ago
        That's a pretty good summary, but honestly the vast majority of journalists will probably just run with the more sensational headline, and D-Wave is very happy to encourage that.
  - derefr 9y ago
    A potentially-enlightening analogy: Is instruction pipelining a form of multiprocessing? (No.) Is hyperthreading? (Sort of, but it's limited and has a separate name for a reason.) Are hyperthreads marketed as SMP cores? (Of course.) Is a chemist's beaker a quantum computer? (No.) Is D-Wave's device? (Sort of, but it's limited and should have a separate name.) Is D-Wave's device marketed as a quantum computer? (Of course.)
  - Dylan16807 9y ago
    Normal transistors are using quantum effects too. The whole point of a "quantum computer" is getting those nonlinear speedups. If the entanglement doesn't speed anything up then it's pretty close to the beaker in terms of relevance.
Tomminn 9y ago
If it's not fighting decoherence then it's not what we mean when we talk about quantum computing. Otherwise I can start saying "technically, you're using a quantum computer right now".
gaze 9y ago
There is, to my knowledge, no evidence of long range coherence in the dwave machine. The qubits have extremely short t2s
WhitneyLand 9y ago
What do you mean a lot has changed? He was referring to D-Wave not being competitive with conventional systems. When did it become generally accepted that D-Wave has shown it could do anything useful significantly faster than a regular computer? Last I heard it was only coming close on 1 or 2 things, but still with no convincing advantage let alone a dramatic one,

whyever 9y ago

> A lot has changed. Could you please give some examples?

kamilner 9y ago

The D-Wave machine is not a full adiabatic quantum computer, though (which would be polynomially equivalent to a universal quantum computer). It does quantum annealing over a pretty restricted set of Hamiltonians. I think it is perfectly reasonable to say it is not a quantum computer, in the same way that not everything performing computation is called a computer. Otherwise---taken to the absurd---why not call a chemist's beaker a quantum computer?

mabbo 9y ago
It's a computing machine taking advantage of certain quantum effects to do computing. Theoretically, it may be able to do certain tasks faster than a traditional computer I'm not saying you're wrong- it's often mislabeled as a quantum computer- but it isn't fair to say it's no better than a chemist's beaker.
- deepnotderp 9y ago
  I guess the problem is that the general public doesn't really know the distinction between quantum annealing and universal quantum computation.
  - hexane360 9y ago
    So maybe articles should include something like: "The D-Wave system uses quantum annealing, which utilizes quantum effects to solve a select few problems much faster than traditional computers. However, it's not as flexible as a universal quantum computer, which could solve a much wider range of problems, including the prime-factorization problem at the heart of modern cryptography."
    - codekilla 9y ago
      I think this is a pretty good summary for an article.
    - deepnotderp 9y ago
      That's a pretty good summary, but honestly the vast majority of journalists will probably just run with the more sensational headline, and D-Wave is very happy to encourage that.
- derefr 9y ago
  A potentially-enlightening analogy: Is instruction pipelining a form of multiprocessing? (No.) Is hyperthreading? (Sort of, but it's limited and has a separate name for a reason.) Are hyperthreads marketed as SMP cores? (Of course.) Is a chemist's beaker a quantum computer? (No.) Is D-Wave's device? (Sort of, but it's limited and should have a separate name.) Is D-Wave's device marketed as a quantum computer? (Of course.)
- Dylan16807 9y ago
  Normal transistors are using quantum effects too. The whole point of a "quantum computer" is getting those nonlinear speedups. If the entanglement doesn't speed anything up then it's pretty close to the beaker in terms of relevance.

Tomminn 9y ago

If it's not fighting decoherence then it's not what we mean when we talk about quantum computing. Otherwise I can start saying "technically, you're using a quantum computer right now".

gaze 9y ago

There is, to my knowledge, no evidence of long range coherence in the dwave machine. The qubits have extremely short t2s

WhitneyLand 9y ago

What do you mean a lot has changed? He was referring to D-Wave not being competitive with conventional systems. When did it become generally accepted that D-Wave has shown it could do anything useful significantly faster than a regular computer? Last I heard it was only coming close on 1 or 2 things, but still with no convincing advantage let alone a dramatic one,