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Im calling BS. We had ‘random projection’ long before anybody started dreaming up use cases for quantum. Seriously, people. When we realize that ‘quantum’ comp

by jl2718 8y ago

Im calling BS. We had ‘random projection’ long before anybody started dreaming up use cases for quantum. Seriously, people. When we realize that ‘quantum’ computing is really just ‘analog’, we’ll see a resurgence in that too. (Which is great actually, because modern analog computers are stunningly capable. And yes, they are the same thing when you realize that the hardware is exactly the same, and sampling away the noise has the same form as solving for decoherence.)

ethn 8y ago
The laws of E&M generalized for Electrical Engineering can even be derived from quantum, BJT and several other equations historically were. Fortunately analog computing seems to be making a rudimentary comeback in the aspects they are actually good for.
- remcob 8y ago
  But the converse is not true. The laws from Quantum Mechanics can not be derived from E&M. This means that the physics covered by QM is strictly larger than E&M. And as my former prof. R. Jozsa showed, this allows for Quantum algorithms that can not be matched by any classical algorithm (see Deutsch-Jozsa algorithm). Analog computers in their ideal form (known as real computers after the real numbers) are also strictly superior to classical computers. But unlike quantum computers, we know for sure that ideal analog computers can not exist. This also follows from QM. (Intuitively, real numbers don't exist in physics and everything ultimately becomes quantized)
  - ethn 8y ago
    That's not true, there are idealizations of ideal analog computers, such as the field computer model of analog computation†. We already have analog computations using continuous-time digital that can solve 32nd order differential equations in less than a millisecond††. We are also unaware of even the theoretical possibility of computation in QM. The noise and sampling problem hasn't been settled (see Kalai for a convincing argument); given the Quantum Threshold needed it becomes suspect when you have the equivalent of 1,000 CPU's for every individual CPU for just a .1% probability of error. Given your same line of reasoning, we are able to measure real numbers, in fact you can derive discrete numbers from real numbers while the converse is not true. Intuitively, discrete numbers don't exist and everything ultimately becomes real numbers. This is obviously a correct following of the stimulating rhetoric yet completely untrue. The ability of derivation from an axiom has nothing to do with the validity of the derivative representations. † https://www.eetimes.com/document.asp?doc_id=1138111 https://www.eetimes.com/document.asp?doc_id=1138111 †† https://ieeexplore.ieee.org/document/7463004/ https://ieeexplore.ieee.org/document/7463004/
    - remcob 8y ago
      My argument was purely theoretical. I fully agree that analog computers currently have more practically attainable advantages over digital computers. I'm also less confident than most people of quantum computers ever overcoming the practical problems, some of which you mentioned. But I do not doubt that the physics itself offers superior computation, even if we may never access it. > we are able to measure real numbers I disagree with you here. I like to believe in the Church-Turing-Deutsch thesis, which implies that reality is ultimately discrete and real numbers are nonphysical. The example you give, time, is indeed a real number in our best models of physics. But this is mostly because we don't know how to quantize it yet. It's one of the biggest open problems in physics. That said, the outcome could indeed be that it is a real number and CTD is wrong.
deleted 8y ago
[deleted]
jkabrg 8y ago
Scott Aaronson explained how this claim is wrong. Quantum computing is not the same thing as "analog computing". See his response to "a quantum computer would merely be a souped-up analog computer" here: https://www.scottaaronson.com/democritus/lec14.html https://www.scottaaronson.com/democritus/lec14.html > And yes, they are the same thing when you realize that the hardware is exactly the same Quantum computers don't actually exist yet. It's a theoretical model. There's no hardware.
- yvdriess 8y ago
  I think it's fair to say quantum computers don't exist yet, but there is plenty of hardware. Although we're still at the wall-throwing stage and nothing seems to have stuck yet. Even for the theoretical models, we have plenty of alternative models. The circuit model is the de-facto standard and a good thought framework, but there are real concerns about it maybe not to being the model to translate into actual hardware. (analogously, lambda calculus vs RTL) It will be interesting to see what alternative or new theoretical models pop up once the quantum computer's equivalent of the transistor surfaces.
- deleted 8y ago
  [deleted]
- Robotbeat 8y ago
  The latter claim is not true. Quantum computers exist, but with lower capabilities than classical ones due to few numbers of entangled qubits.
  - jkabrg 8y ago
    It's not guaranteed that the current hardware will scale to many more qubits. And they haven't passed the threshold to "quantum supremacy".
    - Robotbeat 8y ago
      Sure (although it's likely), but I don't think it's fair to call quantum computing hardware entirely theoretical at this point.

by jl2718 8y ago

ethn 8y ago

The laws of E&M generalized for Electrical Engineering can even be derived from quantum, BJT and several other equations historically were. Fortunately analog computing seems to be making a rudimentary comeback in the aspects they are actually good for.

remcob 8y ago
But the converse is not true. The laws from Quantum Mechanics can not be derived from E&M. This means that the physics covered by QM is strictly larger than E&M. And as my former prof. R. Jozsa showed, this allows for Quantum algorithms that can not be matched by any classical algorithm (see Deutsch-Jozsa algorithm). Analog computers in their ideal form (known as real computers after the real numbers) are also strictly superior to classical computers. But unlike quantum computers, we know for sure that ideal analog computers can not exist. This also follows from QM. (Intuitively, real numbers don't exist in physics and everything ultimately becomes quantized)
- ethn 8y ago
  That's not true, there are idealizations of ideal analog computers, such as the field computer model of analog computation†. We already have analog computations using continuous-time digital that can solve 32nd order differential equations in less than a millisecond††. We are also unaware of even the theoretical possibility of computation in QM. The noise and sampling problem hasn't been settled (see Kalai for a convincing argument); given the Quantum Threshold needed it becomes suspect when you have the equivalent of 1,000 CPU's for every individual CPU for just a .1% probability of error. Given your same line of reasoning, we are able to measure real numbers, in fact you can derive discrete numbers from real numbers while the converse is not true. Intuitively, discrete numbers don't exist and everything ultimately becomes real numbers. This is obviously a correct following of the stimulating rhetoric yet completely untrue. The ability of derivation from an axiom has nothing to do with the validity of the derivative representations. † https://www.eetimes.com/document.asp?doc_id=1138111 https://www.eetimes.com/document.asp?doc_id=1138111 †† https://ieeexplore.ieee.org/document/7463004/ https://ieeexplore.ieee.org/document/7463004/
  - remcob 8y ago
    My argument was purely theoretical. I fully agree that analog computers currently have more practically attainable advantages over digital computers. I'm also less confident than most people of quantum computers ever overcoming the practical problems, some of which you mentioned. But I do not doubt that the physics itself offers superior computation, even if we may never access it. > we are able to measure real numbers I disagree with you here. I like to believe in the Church-Turing-Deutsch thesis, which implies that reality is ultimately discrete and real numbers are nonphysical. The example you give, time, is indeed a real number in our best models of physics. But this is mostly because we don't know how to quantize it yet. It's one of the biggest open problems in physics. That said, the outcome could indeed be that it is a real number and CTD is wrong.

deleted 8y ago

[deleted]

jkabrg 8y ago

Scott Aaronson explained how this claim is wrong. Quantum computing is not the same thing as "analog computing". See his response to "a quantum computer would merely be a souped-up analog computer" here: https://www.scottaaronson.com/democritus/lec14.html https://www.scottaaronson.com/democritus/lec14.html > And yes, they are the same thing when you realize that the hardware is exactly the same Quantum computers don't actually exist yet. It's a theoretical model. There's no hardware.

yvdriess 8y ago
I think it's fair to say quantum computers don't exist yet, but there is plenty of hardware. Although we're still at the wall-throwing stage and nothing seems to have stuck yet. Even for the theoretical models, we have plenty of alternative models. The circuit model is the de-facto standard and a good thought framework, but there are real concerns about it maybe not to being the model to translate into actual hardware. (analogously, lambda calculus vs RTL) It will be interesting to see what alternative or new theoretical models pop up once the quantum computer's equivalent of the transistor surfaces.
deleted 8y ago
[deleted]
Robotbeat 8y ago
The latter claim is not true. Quantum computers exist, but with lower capabilities than classical ones due to few numbers of entangled qubits.
- jkabrg 8y ago
  It's not guaranteed that the current hardware will scale to many more qubits. And they haven't passed the threshold to "quantum supremacy".
  - Robotbeat 8y ago
    Sure (although it's likely), but I don't think it's fair to call quantum computing hardware entirely theoretical at this point.