This always bugs me. Quantum Mechanics isn’t actually that difficult. It has some nasty maths, yes, but that’s mostly slog work, rather than an impossibility. 90% of it is the Schroedinger’s equation + boundary conditions.
The main issue is that you have to abandon the particle model of reality. This is deeply engrained into our brains. If you try and understand it as “Particles + extras”, you will fail. You have to think of it as “Waves + extras”. It then, suddenly makes logical sense.
It does have some interesting implications, however, about deeper reality however. E.g. what exactly IS decoherence, from a physical point of view. Also, what is physically happening, dimensionally, when a wave is complex, or even pure imaginary. These are beyond the scope of QM however.
To elaborate on this, the Schrödinger equation, which describes the dynamics of a single particle, is a wave equation and hence a lot of classical intuition from e.g. electrodynamics can be applied. It is many-body systems, i.e. systems composed of many interacting particles, which is not only mathematically complex but can also defy classical expectations due to emerging phenomena, etc.
The problem of quantum mechanic is that the physics it shows us is not intuitive, and it sometimes breaks other laws of physics.
Quantum intrication means that information travels faster than light for example. Counterfactuality also breaks causality.
It’s not the maths that are the problem, it’s that it doesn’t make physical sense in the world we currently understand. And the equations explain nothing. They merely describe a a world that doesn’t make sense.
Quantum mechanic is like having a machine from the future that does cool things, but you don’t understand how it works. It’s like people did chemistry before they understand what chemistry was. We do uber cool things with it, but it is a spotlight on our ignorance at the same time.
Actually, I think it’s time to reveal, that to some people QM is actually pretty intuitive.
It’s just that the masses and the news media don’t understand it, so they assume that nobody does. The particle worldview is deeply ingrained into many people’s brains, because it’s deeply useful to them on a day-to-day basis. If you loosen that requirement, then there’s literally nothing standing in your way to accept a wave-worldview.
What about the Copenhagen interpretation debate? What about the non-locality?
These are academic debates, not people ones. Saying that quantum mechanic is intuitive is arrogant at best. You may have a perfect understanding of the current theory and how to use it, and you maybe comfortable using it everyday, but then you should be aware of the limits shouldn’t you?
Otherwise it’s like alchemy.