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An important quantum algorithm may be a property of nature

technologyreview.com

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Re: An important quantum algorithm may be a property of nature

#71

Post by knzhou »

Iv wrote: post #35
knzhou wrote: post #21

Earlier quoted context omitted.

This argument proves too much. By that same argument, nuclear fission, ordinary CPUs, steam engines, rockets, helicopters, jets, X-rays, radio waves, superconductivity, superfluidity, air conditioning, liquid helium, liquid nitrogen, the Haber process, the fractional quantum Hall effect, Doppler cooling, graphene, long-distance satellite communication, gravitational waves, and GPS corrections for relativity all don't…

The argument I propose is not a strong one. It is still an argument: if something is possible, why did evolution not use it? There are several possible answers: 1. Life may not have a use for it 2. It may be impossible to achieve with proteins and cells 3. It may not actually be possible For quantum computer I (weakly) believe that 1 and 2 are wrong: evolution and cognition would hugely benefit from quantum accelerat…

The answer is a combination of 1 and 2. Not every computing device is actually useful. For example, you can find plenty of brain parts that look vaguely like GPUs or FPGAs. None that look anything like a standard CPU. This would be basically impossible to build out of cells, and not useful anyway.

The same thing applies to quantum computers. They’re much much harder to build because they’re more delicate. We’re talking about effects that usually are completely destroyed by a single unwanted atom coming in and hitting something. And there are a lot of atoms flying around in cells. Propagating any quantum signal from even one cell to an adjacent one is impossible. Finally they’re less useful. I can’t think of problems a biological brain needs to solve that require even a moderately fast CPU, let alone a quantum computer, which provides speedups over the CPU for only certain specific problems.

But none of this really matters, because your comment is one long isolated demand for rigor. You wave away my long list of examples because you think something very distantly related exists (in which case, with those low standards, quantum computers already exist), or because the examples are clearly impossible or not useful (without equally seriously considering the same for quantum computers). This is what I mean by skepticism of QC being driven mostly by intellectual fashion.

Re: An important quantum algorithm may be a property of nature

#72

Post by knzhou »

kuschku wrote: post #56
knzhou wrote: post #21

Earlier quoted context omitted.

This argument proves too much. By that same argument, nuclear fission, ordinary CPUs, steam engines, rockets, helicopters, jets, X-rays, radio waves, superconductivity, superfluidity, air conditioning, liquid helium, liquid nitrogen, the Haber process, the fractional quantum Hall effect, Doppler cooling, graphene, long-distance satellite communication, gravitational waves, and GPS corrections for relativity all don't…

> nuclear fission https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto... For pretty much every thing you list, nature has something pretty close to it in it. Even nuclear fission.

If you really think you can explain all examples, why did you pick one (by far the easiest one) instead of letting me pick? Let’s see some natural examples that use general relativity, superconductivity, the fractional quantum Hall effect, and superfluidity.

Re: An important quantum algorithm may be a property of nature

#73

Post by knzhou »

raverbashing wrote: post #70
knzhou wrote: post #65

Earlier quoted context omitted.

If your standards are low enough that you would say superconductivity appears in nature, then quantum computing certainly does.

> But of course on planet earth at least it is hard for nature to use things requiring too high or low temperatures So, no, superconductivity probably does not exist in nature

Most candidates for quantum computing also require extremely low temperatures — in fact, lower than the ones for superconductivity.

Re: An important quantum algorithm may be a property of nature

#75

Post by omar_a1 »

lonelappde wrote: post #63
omar_a1 wrote: post #57

Earlier quoted context omitted.

I was also confused about the assertion that biologists dismissed quantum mechanic's affects on biological systems. Biochemists have known about this phenomenon for decades , including photosynthesis.

It seems not so clear cut? This article mentions a controversy on the topic: https://physicsworld.com/a/is-photosynthesis-quantum-ish/

Maybe I'm just using a less narrow definition of quantum mechanics? I'm not referring to the specific quantum phenomena referenced in the article, but to quantum mechanics in general. In other words, since these redox steps are happening on a molecular scale, that of course quantum mechanics falls under its purview - as would anything else happening on this small of a scale.

For instance, not factoring in steric factors (e.g. uncertainty principle) or electron tunneling in the transfer of electrons during photosynthesis or cellular respiration would probably throw off your models. Biochemists are well aware of this; you couldn't effectively understand chemistry without understanding quantum mechanics.

Re: An important quantum algorithm may be a property of nature

#76

Post by SolarNet »

goodmachine wrote: post #23
SolarNet wrote: post #19

Earlier quoted context omitted.

There are sea bacteria that "communicate" in the giga-hertz frequency. But the general point being that large portions of the range are used, like the visible spectrum and the thermal spectrum. x-rays aren't a unique physical phenomena, just a wave length of electromagnetic waves, which is a physical phenomena that life makes excessive use of (photosynthesis, vision).

> There are sea bacteria that "communicate" in the giga-hertz frequency. Wow. Link?

https://ucsdnews.ucsd.edu/pressrelease/can-organisms-sense-v...

Re: An important quantum algorithm may be a property of nature

#77

Post by Ultimatt »

lonelappde wrote: post #63
omar_a1 wrote: post #57

Earlier quoted context omitted.

I was also confused about the assertion that biologists dismissed quantum mechanic's affects on biological systems. Biochemists have known about this phenomenon for decades , including photosynthesis.

It seems not so clear cut? This article mentions a controversy on the topic: https://physicsworld.com/a/is-photosynthesis-quantum-ish/

That article has nothing to do with the OP. There are plenty of effects which are quantum systems in molecular biology, photo chemistry especially and the quantum tunnelling of electrons and ions. That is not what is being discussed here at all. The original blog especially is completely wrong given both the source assertions which are also flawed in their reasoning.

Re: An important quantum algorithm may be a property of nature

#78

Post by Ultimatt »

omar_a1 wrote: post #75
lonelappde wrote: post #63

Earlier quoted context omitted.

It seems not so clear cut? This article mentions a controversy on the topic: https://physicsworld.com/a/is-photosynthesis-quantum-ish/

Maybe I'm just using a less narrow definition of quantum mechanics? I'm not referring to the specific quantum phenomena referenced in the article, but to quantum mechanics in general. In other words, since these redox steps are happening on a molecular scale, that of course quantum mechanics falls under its purview - as would anything else happening on this small of a scale. For instance, not factoring in steric fact…

The difference is mainly of scale, would you describe calcium signalling and calcium ionic standing waves using quantum mechanics? You could. But its not relevant or helpful to do so as that bulk effect doesn't act as a quantum system with quantum behaviours. But a single calcium ion going across a potential gradient in a cation channel does quite often require that description. This is the difference here. Physicists quite often wander into Biology and make quite wild claims without even understanding what is already well known and understood via Chemistry, and sure some of that is inherently just fronting quantum mechanics behind the scenes. But its specifically if a system depends on a quantum effect in a quantum system to understand the observed phenomena. Using numerology rather than reaction rates to describe something being a quantum system isn't good science, it's not even good/exciting/interseting speculation.

Re: An important quantum algorithm may be a property of nature

#79

Post by omar_a1 »

Ultimatt wrote: post #78
omar_a1 wrote: post #75

Earlier quoted context omitted.

Maybe I'm just using a less narrow definition of quantum mechanics? I'm not referring to the specific quantum phenomena referenced in the article, but to quantum mechanics in general. In other words, since these redox steps are happening on a molecular scale, that of course quantum mechanics falls under its purview - as would anything else happening on this small of a scale. For instance, not factoring in steric fact…

The difference is mainly of scale, would you describe calcium signalling and calcium ionic standing waves using quantum mechanics? You could. But its not relevant or helpful to do so as that bulk effect doesn't act as a quantum system with quantum behaviours. But a single calcium ion going across a potential gradient in a cation channel does quite often require that description. This is the difference here. Physicist…

"what is already well known and understood via Chemistry, and sure some of that is inherently just fronting quantum mechanics behind the scenes."

This is actually my main point. I'm not intending to reduce or dismiss (bio)chem through the lens of applied physics. I'm saying that anyone competent in biochem understands these properties on an intuitive level, and further understands that the root of these systems' behavior lies in quantum mechanics, even if they're not crunching wave equations on a daily basis. (That said, discussing s and p orbitals are a pretty routine part of figuring out organic reaction mechanisms.)

The field considers the quantum effects on these systems as a matter of course - as with your example about ion channel flow and caveats on bulk properties versus a single ion. There's still no question that quantum mechanics affects these systems, it's just a question of when it needs to be factored in to not throw off the calculations, and when the scale is large enough that its effects can be considered negligible.

Re: An important quantum algorithm may be a property of nature

#80

Post by emilfihlman »

knzhou wrote: post #21
Iv wrote: post #4

A reason why I allow myself some skepticism on the feasibility of quantum computing is that if it were possible, I would have expected evolution to have used it somehow. If it turns out that protein folding really use a quantum computation, I'll move quantum computers from the "too good to be true" category to the "probably revolutionary stuff that I will see in my lifetime" alongside with nuclear fusion and strong A…

This argument proves too much. By that same argument, nuclear fission, ordinary CPUs, steam engines, rockets, helicopters, jets, X-rays, radio waves, superconductivity, superfluidity, air conditioning, liquid helium, liquid nitrogen, the Haber process, the fractional quantum Hall effect, Doppler cooling, graphene, long-distance satellite communication, gravitational waves, and GPS corrections for relativity all don't…

Wtf? Non even remotely the same argument.
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