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I hate to repeat myself, but analog quantum computers are the future. Digital quantum computers are dead on arrival.

by adamnemecek 8y ago

atomical 8y ago
Why?
- adamnemecek 8y ago
  They are much faster, also can solve optimization problems very naturally. Analog computing used to be a thing before ww2. It was dope for numerical computation but came out of fashion due to rift. Photonic analog quantum computing is the future.
  - olliej 8y ago
    Analog computing has problems of accumulating error that can’t be resolved. The more sequential operations you have to perform, the more the error accrues because unlike any discrete system you have no ability to filter noise. That’s why analog computers “fell out of fashion”. That and the relatively restricted programmability, higher power usage, etc. There are some problems where analog can be faster, but the moment you have consecutive operations you need to accept imprecise answers.
    - adamnemecek 8y ago
      Yes, that’s rift. Photonics don’t have that problem.
      - chongli 8y ago
        When I search ddg with the following query: rift "analog" "computing" -oculus The only relevant result is your comment from this thread.
        trentmb 8y ago
        Accumulated error creates an gap, rift between the true answer and the computed answer.
    - 0815test 8y ago
      Something I've never been able to figure out is whether our modern, deep sub-um and even nm-scale process nodes, are directly usable for anything analog. I suspect that they aren't - that the noise levels are now at a point where even the simplest "gate"-like structures are only useful if used in combination with that "attraction/iteration towards a fix point" mechanism that essentially defines digital electronics (from an "analog" POV), with its inherent resilience to noise. Unfortunately, I even doubt that the question is directly answerable without the sorts of proprietary data that only a multi-billion chip fab would have in the first place.
      - orbifold 8y ago
        They are, certain components even in the smallest process have to be analog. One good process for analog functionality is 22nm SOI, 65nm TSMC also works very well.
    - scottlegrand2 8y ago
      What happens to this rift if it's operating on an equation with a derivative such as the gradient of a neural network? I'm a huge fan of deterministic computation, but we seem to be doing okay without it in deep learning with respect to floating point round off error. Or despite the fact that the computation could be deterministic, the algorithms are written in a way that they are not due to asynchronous accumulation and computation. Would we just get a different minimum each time we run or would something more pernicious occur?
ThePhysicist 8y ago
“Digital” quantum gates on superconducting quantum processors are implemented by changing the system Hamiltonian (by e.g. changing the magnetic flux through the qubit Josephson junction loop or driving the qubits with microwave radiation), so in that sense those quantum processors are analog. Most current quantum algorithms require a series of discrete operations to be performed (e.g. the Grover search is basically a for loop that executes a phase-encoding search function and a diffusion operator in each step), so they require a specific gate set to run them. That said researchers also used superconducting quantum processors to simulate other quantum systems using an analog approach, which is often more efficient than using a digital approach (so-called Trotter based quantum simulation), so both techniques are relevant I’d say.
- adamnemecek 8y ago
  > Most current quantum algorithms require a series of discrete operations to be performed Ok so what? https://en.wikipedia.org/wiki/Continuous-variable_quantum_information https://en.wikipedia.org/wiki/Continuous-variable_quantum_in...
  - ThePhysicist 8y ago
    That means that an analog quantum computer will not give you much advantage when running e.g. Grover search if there’s not a more efficient implementation using a continuous variable approach (which to my knowledge isn’t), so it is not even clear how analog quantum computers could replace the gate-based approach there.
    - adamnemecek 8y ago
      Like, I'm not particularly married to Grover's algorithm or any other gate based algorithm. Throw them all out of the window for all I care.
gaze 8y ago
You keep posting this and it’s just completely unsubstantiated.
- adamnemecek 8y ago
  It’s not. Look into the work of Alessio Serafini https://www.amazon.com/dp/1482246341/ref=cm_sw_r_cp_api_i_UHBXCbN5FZEK https://www.amazon.com/dp/1482246341/ref=cm_sw_r_cp_api_i_UH... Also there have been articles on this very topic posted on hn.
  - deleted 8y ago
    [deleted]

I hate to repeat myself, but analog quantum computers are the future. Digital quantum computers are dead on arrival.

atomical 8y ago

Why?

adamnemecek 8y ago
They are much faster, also can solve optimization problems very naturally. Analog computing used to be a thing before ww2. It was dope for numerical computation but came out of fashion due to rift. Photonic analog quantum computing is the future.
- olliej 8y ago
  Analog computing has problems of accumulating error that can’t be resolved. The more sequential operations you have to perform, the more the error accrues because unlike any discrete system you have no ability to filter noise. That’s why analog computers “fell out of fashion”. That and the relatively restricted programmability, higher power usage, etc. There are some problems where analog can be faster, but the moment you have consecutive operations you need to accept imprecise answers.
  - adamnemecek 8y ago
    Yes, that’s rift. Photonics don’t have that problem.
    - chongli 8y ago
      When I search ddg with the following query: rift "analog" "computing" -oculus The only relevant result is your comment from this thread.
      - trentmb 8y ago
        Accumulated error creates an gap, rift between the true answer and the computed answer.
  - 0815test 8y ago
    Something I've never been able to figure out is whether our modern, deep sub-um and even nm-scale process nodes, are directly usable for anything analog. I suspect that they aren't - that the noise levels are now at a point where even the simplest "gate"-like structures are only useful if used in combination with that "attraction/iteration towards a fix point" mechanism that essentially defines digital electronics (from an "analog" POV), with its inherent resilience to noise. Unfortunately, I even doubt that the question is directly answerable without the sorts of proprietary data that only a multi-billion chip fab would have in the first place.
    - orbifold 8y ago
      They are, certain components even in the smallest process have to be analog. One good process for analog functionality is 22nm SOI, 65nm TSMC also works very well.
  - scottlegrand2 8y ago
    What happens to this rift if it's operating on an equation with a derivative such as the gradient of a neural network? I'm a huge fan of deterministic computation, but we seem to be doing okay without it in deep learning with respect to floating point round off error. Or despite the fact that the computation could be deterministic, the algorithms are written in a way that they are not due to asynchronous accumulation and computation. Would we just get a different minimum each time we run or would something more pernicious occur?

ThePhysicist 8y ago

“Digital” quantum gates on superconducting quantum processors are implemented by changing the system Hamiltonian (by e.g. changing the magnetic flux through the qubit Josephson junction loop or driving the qubits with microwave radiation), so in that sense those quantum processors are analog. Most current quantum algorithms require a series of discrete operations to be performed (e.g. the Grover search is basically a for loop that executes a phase-encoding search function and a diffusion operator in each step), so they require a specific gate set to run them. That said researchers also used superconducting quantum processors to simulate other quantum systems using an analog approach, which is often more efficient than using a digital approach (so-called Trotter based quantum simulation), so both techniques are relevant I’d say.

adamnemecek 8y ago
> Most current quantum algorithms require a series of discrete operations to be performed Ok so what? https://en.wikipedia.org/wiki/Continuous-variable_quantum_information https://en.wikipedia.org/wiki/Continuous-variable_quantum_in...
- ThePhysicist 8y ago
  That means that an analog quantum computer will not give you much advantage when running e.g. Grover search if there’s not a more efficient implementation using a continuous variable approach (which to my knowledge isn’t), so it is not even clear how analog quantum computers could replace the gate-based approach there.
  - adamnemecek 8y ago
    Like, I'm not particularly married to Grover's algorithm or any other gate based algorithm. Throw them all out of the window for all I care.

gaze 8y ago

You keep posting this and it’s just completely unsubstantiated.

adamnemecek 8y ago
It’s not. Look into the work of Alessio Serafini https://www.amazon.com/dp/1482246341/ref=cm_sw_r_cp_api_i_UHBXCbN5FZEK https://www.amazon.com/dp/1482246341/ref=cm_sw_r_cp_api_i_UH... Also there have been articles on this very topic posted on hn.
- deleted 8y ago
  [deleted]