High-temperature Gibbs states are unentangled and efficiently preparable | Hacker News Reader

High-temperature Gibbs states are unentangled and efficiently preparable

arxiv.org

80 pointsKolenCh33 comments

https://www.quantamagazine.org/computer-scientists-prove-tha... gives the more layman-friendly version.

I'm very much approaching this from a level of "I know what some of those words mean", but is this result surprising that quantum systems lose entanglement at high temperatures? Isn't that the whole point of running quantum computers at very low temperatures?

Registering my uneducated guess: Is this implying there was previously hope you could trap a hot system in a Gibbs state and demonstrate nice stable quantum supremacy with those, but they found hot Gibbs states are necessarily all boring and decohered after all?

I believe so, from abstract

> A priori the task of preparing a Gibbs state is a natural candidate for achieving super-polynomial quantum speedups, but our results rule out this possibility above a fixed constant temperature.

So, quantum computers are doomed to be perpetually cool.

Sorry. I couldn't resist.

Loss of resistance is a common phenomenon when you're really, really cool.

That's very metal!

So is this another blow for the free will argument based on quantum entanglement that some posited was happening in the brain? It seems this is another nail in the coffin leaving very few arguments other than mostly solipsistic ones.

That was always the case, to argue otherwise required new physics. I.e. hypothetical physics that probably didn't exist.

I don't know about the free will argument, but this research doesn't really have anything to do with, for example, the possibility of stable entanglement between Posner molecules.

Beyond that, applications of quantum information theory and other quantum tools now extend beyond physics: there's no requirement that something be based on a physically quantum system for it to be useful modeled by quantum tools.

All in all, there are lot of ways to use quantum/quantum-like/post-quantum models now, both within physics and outside of it. Quantum stuff just isn't as monolithic as many orthodox physicists would suggest.

You can't use it outside of physics, because the combination of digital computers and human brains this hypothetical stuff runs on is in physics. GR (general relativity) + objective collapse (re. quantum physics) does not give you enough for the high-temperature speedups you want.

I spoke of "physics" first and foremost as a scientific paradigm. It's a time-honored variety of applied mathematics.

The map is not the territory, regardless of how accurately its models describe reality. The standard model is great, don't get me wrong, but it's still a map, one of many.

"Physical" models are no longer the only context where quantum tools are relevant or useful. Look into Jerome Busemeyer if you want to learn more.

> The map is not the territory.

Yes, that's why I spoke of GR + objective collapse. GR + objective collapse is not the territory, most people including Penrose will tell you that. What some of his readers apparently don't get is that he supports GR + objective collapse only to the extent that there's "only one true objective world" (because he likes that for aesthetic reasons), and then immediately turns around and rejects it because there's no space for free will.

Very interesting, thank you for the scientist reference. Looking at Wikipedia I found that "...the identification of quantum structures in cognitive phenomena does not presuppose the existence of microscopic quantum processes in the human brain.". This highlights your comment.

Wonder if it says anything against the idea that the whole universe has to be considered as a gigantic entangled quantum state, and that even gravity might arise from that entanglement?

If it is not physics, shouldn’t we give it a different name that liberates it from all the physical imagery?

Something like “c* algebra based models”. “Quantum” carries to much baggage by now, things like “quantum healing” are just scams.

The free will argument has always been junk though because it's based on a bait-and-switch: "quantum mechanics is random, and therefore the future is not predictable with certainty" gets turned around into "so I have free independent will".

You should be able to see the problem: random events are not free will, they're random. The only thing it concludes is that some part of your perceived decision making is no longer predictable - it doesn't mean "you" are in charge of it somehow.

My credentials are: I really like reading and watching scientific fiction.

I think the idea of free will and quantum randomness is that the randomness can be influenced by :magic: something else :magic:, e.g., a soul/spirit/diety.

Combining any of wave theory, quantum entanglement, quantum randomness, and string theory and you've got all sorts of fun ways to attempt to justify the idea of free will.

(not taking sides on free will here, I'm just stating there are nearly infinite reasons for it's existence that will be made)

Yes, that's what I mean by "new physics".

Not being snarky, but when would "new physics" just became a "theory"? These ideas aren't all that new.

I didn't say they can't be theories. I don't think Penrose ever got that far though. There theoretically were some measurements that would distinguish the idea, but since it was attached to quantum gravity the math was never worked out.

Not arguing against the philosophy here, but wouldn't sufficiently unpredictable make it indistinguishable from free will, for practical purposes?

No. Does a browser have free will? No, it's bound to either the instructions from the OS/Processor or the user input.

> Does a browser have free will?

I feel like a browser is lacking some other prerequisites that disqualifies it from being a good example in this case. At least my browser doesn't claim to be conscious.

Who cares if it's conscious or not. Chemistry and Physics are the same everywhere. You are atoms are not magical.

I would say when it comes to free will you have no choice but to believe in it.

It doesn't matter how does it work inside. There's no free will, you are bound to the action of the physics from the Universe. Period.

What makes you say that? Have you read serious arguments against this view (ideally from academic philosophers, not somebody like me on HN!)?

What if free will is part of the formula in the the laws of the universe?

Free will doesn't exist as you are part of the universe. Thus, you have the same free will as chemical reactions in your brain. None.

What if it's the other way around: the universe is part of you. Also consider that determinism can't exist without free will, as darkness cannot exist without light, or warmth can't exist without cold. They're mutually dependent on each other.

Free will doesn’t make sense in any case. Either your will is causally determined, or there is a truly random component, which however doesn’t bring you any closer to influencing your own will.

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