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Comment by lisper | Hacker News Reader

This is not a "quantum sense", it's a mechanism for sensing (non-quantum) magnetic fields that happens to rely on a quantum mechanical effect. But ultimately everything that happens in our universe relies on quantum mechanical effects, to that's not quite as esoteric as the headline is trying to make it appear.

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The distinction here is that this effect requires a quantum-mechanical understanding of the world to be understood at the core. It's not like the simple movement of a ball in a parabola, which can be explained in classical terms.

The same could be said about sense of smell. And frankly any of the other senses. Even touch, if you realize that the atoms in your hand never really "touch" other objects.

Depends how you define “touch” doesn’t it? It’s not like the atoms have sharp boundaries which fall short of coinciding with the boundaries of other atoms,

what should it even mean to say that they do or don’t touch?

I don’t know much of anything about how smell works. Does it involve quantum mechanics in ways which don’t fall under “chemistry” (with chemistry being an implication of quantum mechanics) ?

I think “has to be understood in terms of quantum mechanics beyond just chemistry” is a reasonable distinction to make, and applies to the way these birds work.

> I don’t know much of anything about how smell works. Does it involve quantum mechanics in ways which don’t fall under “chemistry” (with chemistry being an implication of quantum mechanics) ?

Arguably, yes. You could call smell a chemical sensor, but it's not sensing chemicals through a chemical reaction. Instead, it's sensing the modes of excitation of a molecule, i.e. the distribution of available state transitions, which is inherently quantum mechanical.

Cool! I didn’t know that. Thanks!

That's interesting. Do you have a reference?

No, sorry. I don't remember where I first read about this, but it was a story about a perfume manufacturer successfully using IR gas chromatography to synthetically recreate an expensive perfume component (or something like that), where other techniques had failed. I don't know if there has been any subsequent research publications that definitively demonstrate what's going on.

It's possible that shape matters, too, as it does for other receptors. Either way, quantum mechanics is still critical for understanding the mechanism.

Found this:

https://www.bbc.com/news/science-environment-21150046

Apparently, it's controversial.

It might be more accurate to say that every atom in the universe are touching just a little, but the closer together they are, the more they touch. It’s a matter of threshold of probability, really. The inputs to the biological sensorium remain linear off the scale of discernment, but there are mechanisms involved in the sensing that have a nonlinear signal response, giving the very useful illusion of binary edges to sensory phenomena.

The most interesting part is very similar to phosphorescence https://en.wikipedia.org/wiki/Phosphorescence#Introduction Look at the figure 1A in the research paper https://www.pnas.org/content/118/3/e2018043118

Note that the diagram in Fig 1A is more complicated than the one in Wikipedia, because in this case the process involve some additional chemical steps.

If phosphorescence a chemical or a quantum phenomena? https://xkcd.com/435/

With some random search in Google I found this: https://www.sciencedirect.com/topics/chemistry/triplet-state It's somewhat relevant because the cause of phosphorescence and what is happening in this articles is caused by triplets. I want to highlight that if I'd want to ask more about these articles, in half of them I'd ask a Chemist and in the other half a Physicist. (In both cases, one that is specialized in these things that are between the fields.)

my first thought was the same, but I still had an intuition that it makes sense to call this sort of thing quantum as opposed to other, say, chemical-based senses which, although still at some level obviously relying on quantum physics, are more readily explained by using higher level concepts.

I suppose it comes down to emergent phenomena: what's the lowest-level concept you HAVE to invoke to understand what's going on here? when you want to explain how taste buds work, you can talk about neural paths and chemical chains, and even though each of those things relies on quantum physics to exist, you don't have to invoke the concepts or objects of the quantum world to understand the phenomenon in question. but with this particular phenomenon, you do. you can't just explain how this works with higher level concepts, you have to get low down.

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