Nature of "Real" Applications Quantum Mechanics I've heard of several applications of quantum mechanics such as atomic clocks, transistors, lasers, etc. I understand how we need quantum mechanics to understand what's going on, but how exactly is quantum mechanics used in any sort of "real world" application? It seems like it would be crazy to use QM to calculate a lot of things. I'm an engineering student so I've only done basic calculations in QM such as quantum harmonic oscillators, simple potential wells, etc. and even in relatively simple stuff it seems like the problems are purely academic. Doing problems definitely can be interesting and gives insight into how QM works, but seems unrealistic to work with. So is QM mostly used qualitatively when actually designing something or even less directly as to just get the idea of what could be done like with Einstein coming up with the idea behind the laser?