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> Quantum computers are analog devices! I've read this before used disparagingly; quantum is "just analog." Is that really the case? Is quantum computing is

> Quantum computers are analog devices! I've read this before used disparagingly; quantum is "just analog." Is that really the case? Is quantum computing is simply the ultimate miniaturization of analog computing? Reading the recently disclosed "quantum superiority" paper from Google[1] that was somehow leaked by NASA one could be convinced that quantum is "just analog." The paper deals in "resonance", "coupling", "filter" and "attenuator"; it reads like the description of a superheterodyne transceiver; analog RF. This reverse-engineering story points out that the speed of analog computation is due to the effectively parallel processing of the op amps. This aligns with the description of qubits also working in parallel. One thing is certain; classical analog computers are vastly easier to understand. An op amp is simply an electrical function. So now I'm really intrigued; Is quantum computing really "just" faster and smaller analog? [1] The actual PDF has appeared: https://drive.google.com/file/d/19lv8p1fB47z1pEZVlfDXhop082Lc-kdD/view https://drive.google.com/file/d/19lv8p1fB47z1pEZVlfDXhop082L...

varjag 7y ago
> The paper deals in "resonance", "coupling", "filter" and "attenuator"; it reads like the description of a superheterodyne transceiver; analog RF. This is the scaffolding for measuring and manipulating quantum states. Quantum computing itself is not "analog" in the original, signal processing meaning of the word: the states are not isomorphic analogies for modelled physical processes.
- klyrs 7y ago
  It's true that qubit states are inherently quantized. However, the control circuitry, couplers or gates, and often the qubits themselves, are analog devices. The "un-sexy" truth is that calibration is one of the most difficult parts of producing a useful quantum computer.
  - varjag 7y ago
    Sure, and any PC has tons of analog circuits too, for example speaker output. The calibration and scaffolding in quantum computers isn't a model of anything. Not in the same way as opamp board in this article is an analogy of integral.
comex 7y ago
Digital circuits also process everything in parallel. It's only CPUs (i.e. one particular thing you can build out of a digital circuit) that have trouble with it, really... Quantum computing is (somewhat) analog in nature, but it's not "just analog". In theory, taking advantage of quantum physics in the computer gives you an improvement in asymptotic complexity (not just a constant factor speedup), one that you can't get any other way.

varjag 7y ago

> The paper deals in "resonance", "coupling", "filter" and "attenuator"; it reads like the description of a superheterodyne transceiver; analog RF. This is the scaffolding for measuring and manipulating quantum states. Quantum computing itself is not "analog" in the original, signal processing meaning of the word: the states are not isomorphic analogies for modelled physical processes.

klyrs 7y ago
It's true that qubit states are inherently quantized. However, the control circuitry, couplers or gates, and often the qubits themselves, are analog devices. The "un-sexy" truth is that calibration is one of the most difficult parts of producing a useful quantum computer.
- varjag 7y ago
  Sure, and any PC has tons of analog circuits too, for example speaker output. The calibration and scaffolding in quantum computers isn't a model of anything. Not in the same way as opamp board in this article is an analogy of integral.

comex 7y ago

Digital circuits also process everything in parallel. It's only CPUs (i.e. one particular thing you can build out of a digital circuit) that have trouble with it, really... Quantum computing is (somewhat) analog in nature, but it's not "just analog". In theory, taking advantage of quantum physics in the computer gives you an improvement in asymptotic complexity (not just a constant factor speedup), one that you can't get any other way.