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).