Canonical everyday-life example of a technology that could not work without humans mastering QM in analogy to the application of GR in GPS?

Question

The GPS is a very handy example in explaining to a broad audience why it is useful for humanity to know the laws of general relativity. It nicely bridges the abstract theory with daily life technologies! I'd like to know an analogous example of a technology which could not have been developed by engineers who didn't understand the rules of quantum mechanics. (I guess that I should say quantum mechanics, because asking for a particle physics application could be too early.)

To bound the question:

• No future applications (e.g. teleportation).
• No uncommon ones (for, who has a quantum computer at home?).
• A less frequently-cited example than the laser, please.
• If possible, for sake of simplicity, we'll allow that the quantum theory appears in form of a small correction to the classical one (just like one doesn't need the full apparatus of general relativity to deduce the gravitational red-shift).

Answer 1

How about diagnostic methods in modern medicine?

Nuclear magnetic resonance (NMR) - it wouldn't even make sense to talk about it without quantum mechanics, because it depends on the quantum mechanical concept of spin

Positron emission tomography - hey, the name says it all, not only do you apply quantum mechanics, but you have a direct application of antimatter

X-ray scanning, scintigraphy and many, many more... nuclear medicine is full of direct applications of nuclear, particle and quantum physics... It's even common to find particle accelerators in oncology departments for cancer therapy! And what's a better application to mention to a common layman than "curing cancer"?

I'm sure you'll find lots of examples from medicine on the Internet :)

Answer 2

The first common application that comes to my mind would definitely be the LED. From there on, everything that has even remotely to do with a semi-conductor. Furthermore, these days all chemical reactivity is understood in terms of quantum mechanics.

Answer 3

Quantum theory is so integrated into every day life that I think most people would find it very difficult to imagine a world in which we'd never developed quantum mechanics.

First, without quantum physics, we would probably not understand the behavior of materials well enough to have invented modern semi-conductors. No modern electronics. No computers. No internet. No video games. No dot-com boom. No Facebook. No mass video communication. (We'd still have transistors, so we'd still have radio and 1960's quality TVs.)

We also wouldn't have developed anything like modern chemistry without quantum mechanics. We wouldn't understand why elements behave the way they do. We'd be lacking the basis for biochemistry. I think it's quite plausible that we wouldn't know about DNA or have a clue how proteins work. No hope of rational drug design. No clue how diseases work.

It's not just quantum mechanics that shapes our world either. Without quantum field theory, we wouldn't have any clue about nuclear physics. No nuclear power plants. (That's about 10% of the world's electricity budget. Doesn't sound like much, but I don't think we'd be happy if it abruptly disappeared.) Also, no nuclear weapons. Maybe this is a good thing, but I think even Harry Turtledove would have trouble imagining what the past 70 years of history would have been like without them.

Answer 4

To list some more applications:

• UltraPrecise clocks. The most precise one, was built at NIST in 2010, based on a single aluminum atom (ion), in an ion trap. As is reported here The clock would neither gain nor lose one second in about 3.7 billion years. These clocks have many applications, from fundamental physics researches to GPS and navigation systems.

• Quantum random number generators,(see here) which are available now, have many applications. In cryptography, you need a random source of numbers (for example for key generation). Quantum random number generators are used to provide these random numbers, using the random nature of quantum world. (much better than traditional pseudorandom numbers) Also, the quality of stochastic simulations depends on the quality (randomness) of used random numbers. ( BTW, there are online quantum random bit generators available, which generate random numbers in a lab by measuring some quantum quantity. For example see here and here. This (2nd) site has some other *fun stuff*s too!)

• Quantum communications. Already has short-range applications.(for example, in Australia)

Answer 5

The quantum mechanical semiconductor-based transistor is the technological backbone behind all modern computers. So the internet runs off quantum mechanics.

It is a correction in the sense that you don't need quantum mechanical principals to build computers, or even transistors, but semiconductor technology makes the computers small enough to be as ubiquitous as they've become.

Answer 6

I think quantum engineering of magnetism could be an appropriate answer to the question.

Indeed the microscopic origin of magnetic field produced by iron for instance can be explained thanks to the old microscopic model by Ampere relying on a classical macroscopic electrodynamical analogy. But this model is not fully consistent with classical physics of course. It requires a quantum explanation. I use to say to my students at high school that natural magnetism is a nice exemple of quantordinary phenomenon (weak diamagnetism) while superconductivity for instance is quantastic (strong diamagnetism)!

To be more definite about quantum engineering I am basically thinking about high-tech making it possible to select, organize, design materials at the nanoscale thus implying quantum effects.

As a good example of quantum engineering of magnetism I would mention : giant magnetoresistance whose discovery was rewarded with a Noble prize to Albert Fert and Peter Grünberg in 2007!. This totally technology became standard in the read-out heads of hard disks and was of crucial importance to the accelerating trend of hard disk miniaturization.