Quantum physics

It can't at least if you mean directly, if your talking about quantum encryption or computing then that's different.

It's accepted that given the lifetime of the universe some pretty bizarre quantum mechanics effect could effect the macro world, ie you could disappear and end up on Mars, but there not likely to happen every day or even guaranteed to happen at all. And let's face it most effects would be so small no one would notice anyway, it'd be like a grain of sand disappearing on a beach and reappearing on another part of the beach.

Of course if quantum mechanics effects the way our minds work? Very controversial idea, by Penrose and others, then every odd thought or inspiration or bit of deja vu or tangental idea might be something to do with QM?

I think the consensus is no, not really and if you want to discuss it, do what I did and put it in the philosophy section where you can wave your arms around as much as you like

 

If you mean: in what way do we really need quantum physics in order to do something practical in the real world, which wouldn't be accessible otherwise (like purely empirically) ? Well, I don't know. Of course, many high-tech applications are directly INSPIRED by ideas from quantum theory. Many phenomena used daily are only entirely understandable in the frame of quantum theory. But technology doesn't always need understanding (something I learned quite late in my career !). One can have a totally wrong picture of what goes on, but nevertheless have quite useful phenomenological models, tuned to empirical data.

I'm thinking, for instance, about transistors. Of course, the electrical behaviour of a set of layers of semiconductors needs ideas from quantum mechanics: the very ideas of conduction band, valence band, doping, impurities etc... need quantum theory. However, one can get quite far in describing the functioning of transistors by using the "semiclassical model" (you know: the density of "holes" and "electrons", their "mobilities", their diffusion equation etc...). So, to do actual modeling of transistors, I'm not sure you really practically use the full machinery of quantum theory. Maybe for some advanced structures one has to, I don't know.

Another application: lasers. Again, although lasers are a typical quantum-optical phenomenon, the semi-classical theory of lasers is quite satisfying, and I'm not sure that genuine laser builders go through the whole quantum optics machinery to optimise their stuff - I guess they rather do it empirically.

So I'm also interested in knowing in what areas of technology one really NEEDS the entire machinery of quantum mechanics in order to ACTUALLY DESIGN stuff. Mind you: I'm not talking about the toy model which enables one to understand essentially how the thing is supposed to be working, but which is not really used in the practical design. I'm talking about using the wavefunction stuff in order to say: |ok, this layer must then be 102.5 nanometers thick", and this 102.5 comes out of a formal quantum-mechanical calculation, and not about some empirically fitted model. I'm also not talking about, say, scientific spectroscopy or the like. I'm talking about where genuine formal quantum theory is used, with its full wavefunction machinery, in order to do some technological design. I have the impression that these occasions are, though I'm sure they exist, pretty rare, and I'd like to know something about it.

 

But there is a difference between using it NOW, versus how these things came into being in the first place. Bardeen had to use quite a significant amount of his theoretical expertise to be able to calculate and help design the first transistor that was made. So it didn't come about out of trial and error without knowing any quantum mechanics. But once the physics is well-established, then subsequent use and production need not be acutely aware of the underlying physics. The same could be said about lasers, etc.

When we start dealing with more exotic semiconductors, or when we try to make even more complex structures, we inevitably have to go back to the theoretical description. We are seeing this more now with these mutilayered structures and with nanotechnology. This clearly shows that yes, these theoretical foundations are very much required whenever we want to try something new.

Zz.

 

Sure, I hope I wasn't saying the opposite.

The point is, and it is not something I want to state, but just due to the limited experience I have, I'm simply not aware (which doesn't mean it doesn't exist!) of genuine *technological* applications (rather than scientific ones) where one needs to do full quantum calculations "on a daily basis" in order to improve upon the production process. I mean, if I would know where this happens, I'd think I'd redirect myself to that domain if possible

I'm comparing this to, say, thermodynamics or continuum mechanics, or in electronics, where people use, for practical day-to-day purposes, software packages which use finite-element techniques which are solutions to the basic equations of continuum mechanics, or for heat transport or of the Maxwell equations or things of that kind. I'm not aware of such uses for the quantum formalism (unless in the chemical industry, one does a lot of quantum chemistry, but I'm not aware of that).

Maybe there ARE such fields of technology. It might be (but I'm not sure) that certain parts of the semiconductor industry do this. I'm simply not aware of it.

Again, I'm talking of the day-to-day "engineering" approach. Not the scientist who demonstrates a potential new application in his national lab.

 

Well, I know (that is, have heard) that microelectronics are now getting so small that they're beginning to confine the individual electron wavefunctions and causing very weird effects, limiting the minimum size of transistors and such. Just a quick example.

 

Yes that would be quantum electron tunnelling, where electrons pass from one part of a circuit to another, because of the very small distances involved quantum effects come into play, this ultimately limits the size of the components on a microchip and the distances between tracks. Of course a quantum computer would not have this problem, but we're nowhere close to resolving the issues there yet from what I have read.

I apologise to the OP, I think I misinterpreted your question

http://physicsweb.org/articles/world/14/6/3

 

But the "day-to-day" usage need not be referring to engineers either. We could refer such usage of an ordinary person. I would say that even when one is ignorant of the underlying physics of semiconductors, one is STILL making use of the physics of it. So in my opinion, simply by pointing out all the modern electronics is a sufficient illustration to the OP that we do "apply" quantum mechanics daily, because they were designed and understood based on it.

Zz.