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Both of those papers, and others like it, are by single authors in philosophy journals, not physics journals. I don't think they are 'serious' in the same way.

by Mizza 5y ago

Both of those papers, and others like it, are by single authors in philosophy journals, not physics journals. I don't think they are 'serious' in the same way. That Arxiv one is particularly bad.

naasking 5y ago
"Particularly bad" in what sense? The notion that quantum computation happens in parallel universes is a philosophical position, not a scientific one, so of course philosophers of science are evaluating it.
- Mizza 5y ago
  It introduces the fundamental question but never answers it. He quotes Deutsch partially, "explain how Shor’s algorithm works" - but doesn't answer this question. He also leaves out the important part of the quote: "To those who still cling to a single-universe world-view, I issue this challenge: explain how Shor’s algorithm works. I do not merely mean predict that it will work, which is merely a matter of solving a few uncontroversial equations. I mean provide an explanation. When Shor’s algorithm has factorized a number, using 10^500 or so times the computational resources than can be seen to be present, where was the number factorized? There are only about 10^80 atoms in the entire visible universe, an utterly minuscule number compared with 10^500. So if the visible universe were the extent of physical reality, physical reality would not even remotely contain the resources required to factorize such a large number. Who did factorize it, then? How, and where, was the computation performed?" Computation is real - it requires matter and energy. If Shor's algorithm can factor a number so large that it would require more matter than there is available in the universe: _where is the computation occurring_? I have never seen this plainly addressed. I'm a layman, of course, which I why I would hope she'd break this argument down in her MWI video.
  - jessaustin 5y ago
    There are only about 1080 atoms in the entire visible universe... Should this be read as 10^80? The way it's written is confusing.
    - trenchgun 5y ago
      Indeed. Those sentences should be like this: "When Shor’s algorithm has factorized a number, using 10^500 or so times the computational resources than can be seen to be present, where was the number factorized? There are only about 10^80 atoms in the entire visible universe, an utterly minuscule number compared with 10^500."
  - trenchgun 5y ago
    You dropped these: ^^^
  - naasking 5y ago
    > but doesn't answer this question The author doesn't have to answer that question to dispute Deutsch's alleged answer. Secondly, Deutsch's challenge of explaining Shor's algorithm presupposes that quantum computation requires an explanation in terms of classical computation. While I'm sympathetic to that view, this assumption is easily rejected by people who don't view reality as fundamentally classical or local. So for these people, there is no challenge to meet. Thirdly, while you can speculate that Shor's algorithm will scale to factoring numbers so large they require more atoms than are in the universe, no one has demonstrated that this is the case. Just because our current models describe this happening, that doesn't mean the model corresponds to what will actually happen in reality. It could easily be the case that the model is not accounting for noise or other factors that will prevent entanglement from scaling to the levels you describe. This is the position of some determinists, in which case Deutsch's challenge is also neutered. Finally, other interpretations of QM can also provide explanations for speedups. For instance, any interpretation of QM that accepts its non-locality has an escape hatch via relativity: non-locality is effectively time travel in GR, but in a form that cannot be exploited for superluminal signalling. There are many other possible answers given by other interpretations of QM. I personally think it's an interesting question, but it's not a compelling argument for many worlds, not least because the "many worlds as parallel computations" doesn't actually work beyond trivial examples. > Computation is real - it requires matter and energy. Yes, classical bits require a certain amount of matter and energy, but qubits do not have the same matter and energy requirements, which seems to be what you're expecting. If you expect there to be an answer of this sort, then I think you must give up believing that quantum computation will scale. Basically, you are expecting reality to actually be classical, and so have some deterministic classical computation happening behind the scenes (hidden variables), and these hidden variables will more than likely disrupt scaling quantum computations.

by Mizza 5y ago

Both of those papers, and others like it, are by single authors in philosophy journals, not physics journals. I don't think they are 'serious' in the same way. That Arxiv one is particularly bad.

naasking 5y ago

"Particularly bad" in what sense? The notion that quantum computation happens in parallel universes is a philosophical position, not a scientific one, so of course philosophers of science are evaluating it.

Mizza 5y ago
It introduces the fundamental question but never answers it. He quotes Deutsch partially, "explain how Shor’s algorithm works" - but doesn't answer this question. He also leaves out the important part of the quote: "To those who still cling to a single-universe world-view, I issue this challenge: explain how Shor’s algorithm works. I do not merely mean predict that it will work, which is merely a matter of solving a few uncontroversial equations. I mean provide an explanation. When Shor’s algorithm has factorized a number, using 10^500 or so times the computational resources than can be seen to be present, where was the number factorized? There are only about 10^80 atoms in the entire visible universe, an utterly minuscule number compared with 10^500. So if the visible universe were the extent of physical reality, physical reality would not even remotely contain the resources required to factorize such a large number. Who did factorize it, then? How, and where, was the computation performed?" Computation is real - it requires matter and energy. If Shor's algorithm can factor a number so large that it would require more matter than there is available in the universe: _where is the computation occurring_? I have never seen this plainly addressed. I'm a layman, of course, which I why I would hope she'd break this argument down in her MWI video.
- jessaustin 5y ago
  There are only about 1080 atoms in the entire visible universe... Should this be read as 10^80? The way it's written is confusing.
  - trenchgun 5y ago
    Indeed. Those sentences should be like this: "When Shor’s algorithm has factorized a number, using 10^500 or so times the computational resources than can be seen to be present, where was the number factorized? There are only about 10^80 atoms in the entire visible universe, an utterly minuscule number compared with 10^500."
- trenchgun 5y ago
  You dropped these: ^^^
- naasking 5y ago
  > but doesn't answer this question The author doesn't have to answer that question to dispute Deutsch's alleged answer. Secondly, Deutsch's challenge of explaining Shor's algorithm presupposes that quantum computation requires an explanation in terms of classical computation. While I'm sympathetic to that view, this assumption is easily rejected by people who don't view reality as fundamentally classical or local. So for these people, there is no challenge to meet. Thirdly, while you can speculate that Shor's algorithm will scale to factoring numbers so large they require more atoms than are in the universe, no one has demonstrated that this is the case. Just because our current models describe this happening, that doesn't mean the model corresponds to what will actually happen in reality. It could easily be the case that the model is not accounting for noise or other factors that will prevent entanglement from scaling to the levels you describe. This is the position of some determinists, in which case Deutsch's challenge is also neutered. Finally, other interpretations of QM can also provide explanations for speedups. For instance, any interpretation of QM that accepts its non-locality has an escape hatch via relativity: non-locality is effectively time travel in GR, but in a form that cannot be exploited for superluminal signalling. There are many other possible answers given by other interpretations of QM. I personally think it's an interesting question, but it's not a compelling argument for many worlds, not least because the "many worlds as parallel computations" doesn't actually work beyond trivial examples. > Computation is real - it requires matter and energy. Yes, classical bits require a certain amount of matter and energy, but qubits do not have the same matter and energy requirements, which seems to be what you're expecting. If you expect there to be an answer of this sort, then I think you must give up believing that quantum computation will scale. Basically, you are expecting reality to actually be classical, and so have some deterministic classical computation happening behind the scenes (hidden variables), and these hidden variables will more than likely disrupt scaling quantum computations.