Comment by dtj1123
1 day ago
We understand quantum mechanics well enough to build machines that depend almost entirely on quantum principles.
It sounds all superior and mysterious to quote Feynman here, but the fact is many people absolutely do understand quantum mechanics.
>It sounds all superior and mysterious to quote Feynman here,
It isn't about being superior, mysterious, or clever. The following "nobody understands" type of quips and thought experiments are different ways of saying our intuitions don't help us understand it :
- "God does not play dice with the universe.", Albert Einstein
- "Shut up and calculate", N. David Mermin
- "Schrödinger's cat" being both alive and dead
- various interpretations/analogies explaining quantum physics leading to absurdities or contradictions
Yes, humanity has harnessed quantum mechanics with mathematic frameworks and repeatable experiments to make useful things... but that's a different layer of "understanding" than the deeper levels in the above quotes.
"Nobody understands what gravity is." ... Wait, if nobody "understands" gravity, how did we send people to the moon?!?
Because those are different usages of the word "understand".
"Understand" means "Have a reasonable metaphor for."
Our monkey minds evolved to throw rocks at birds, and our metaphors are based on concepts like position, velocity, and temperature. We added first-level abstractions like energy and cause-and-effect, then built higher level abstractions on those basic concepts.
QM clearly doesn't work like that. It's probabilistic, possibly non-local, possibly subjective, possibly a holographic projection of some underlying reality that is nothing like this one, and its relationship with causality is slippery.
We have a mathematical UI for it, but that's not at all the same thing as understanding the machinery on the other side of the UI.
A very sharp and succinct statement of the problem!
I think the disconnect here is the use of the word "understand". What Feynman presumably meant was really "interpret" not "understand", and theories are not made to be interpreted - they are made to make experimental predictions.
Many people of course, Feynman obviously included, understand the theory in the sense of knowing how to correctly apply it to make predictions.
If one does understand quantum mechanics well enough to use it, then one also understands that there are aspects of it we do not fully understand.
You can make an identical argument with respect to classical physics, e.g. outstanding issues in fluid dynamics or statistical mechanics.
Nobody takes this to mean that classical physics is generally incomprehensible.
The difference is that the part we do not understand about QM is rather fundamental to its interpretation, while in classical physics it is more a problem of understanding its consequences in complex scenarios.
Can’t we say the same about LLMs? Yet interpretability of them is rough.
We can build black boxes and exploit the behavior of what we see.
But we can’t always go to deeper and deeper layers of understanding.
QM is not a black boxes we built but one could perhaps say it’s a black box that we see.
No, I do not claim I am expert at understanding at how LLMs operate, but there is a huge difference - we can measure changes in models and even identify what part of model is used - it is clearly a niche thing to do and not particularly interesting to many people(and not to me as well, unless those LLMs will be able to replicate brains - in future, then I would be biting my nails that I have ignored the basics), but there is no such issue on dissecting and identifying how bits are shuffled around, unlike with QM.
For QM the main issue is that we are barely able to see results of that black box and have to make guesses even about observable results, because what we see is result of particle long gone and the result has been a mess of paths that it took. And basically we are operating at identifying single particle, while clearly the path that particle took was defined by other particles and "gravity"? from interacting with other particles bumping it around. I'm even less knowledgeable when it comes to QM terminology, but I get impression that most of the commenters here simply are parroting things they have read or being taught without actually trying to understand and taking into account all the unresolved problems in QM, which is why so many of them sounds so confident is my guess. Because knowing limitations of my brain I would be not so confident of anything, only because of massive load of unresolved issues that QM has.
Listen, people were able to make calendars by observing skies and assuming that Sun was orbiting Earth. It is not exactly the same, but very much how people understand QM - they do not need to known mechanics, but observing end results is enough to "understand" how it functions.
Also billions of people understand how to operate mobile phones, but "understanding how they operate" would be rather stretch and even the biggest specialists of QM have understanding only on how to interpret end results in QM - at best and that is basically it.
Quite frankly, I'm confused about these bold statements. I assume there seems to be some knowledge background of what you are saying - it very much reminds me what stupid strawman arguments I had in high school with my schoolmates then as a part of learning process, but rather far from actual wisdom.
Forgive my ignorance but which machines depend almost entirely on quantum principles?
The processor of the computer you are writing your question on is using tunnelling transistors.
Modern processors are designed to minimise quantum effects, because phenomena like tunnelling create inefficient leakage currents.
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Or we understand just enough to make things and instruments that only work on (and up to) the layer that we understand.
Ancient humans could build boats 5000 years ago and expand throughout the planet, but they didn't know about water being made up of hydrogen+oxygen, or the tides being caused by the moon, etc.
Their calculations served them on the layer they operated on.
> the tides being caused by the moon
Mostly because people around the mediterranean sea didn't have to care, tides being so small there. Yet the Greek had fairly advanced models of tide schedules.
Pretty sure peoples that were experiencing bigger tides and depended on it e.g for fishing figured out the relationship with the moon pretty quickly, whatever esoteric reason they may have plastered upon it.
We understand part of it but not how it works.
does building those machines require us to fully understand quantum mechanics?