Wait? I thought patents required a working prototype. If that's not the case I'm going to patent everything, but with quantum computers. And then everything, but with nanotechnology.
The following are the requirements for filing a patent:
1. Usefulness
2. Novelty: The invention must not have existed from before
3. Non-obviousness: The invention must not be obvious to those skilled in the prior art.
When filing a patent application, you are required to describe the invention in full, including the best mode.
So while a working prototype is not required, satisfying 1, 2 and 3 above is still theoretically hard and requires a lot of work for filing a good patent. The issue is that the system is abused as each one of 1, 2 and 3 are subjective more or less.
While not explicitly stated, I believe the concept described in the application must be correct [1]! Since a prototype is not required, it is sometimes the case that things that do not even work the way inventors thought get the patent granted anyways.
Finally, just for completion sake, there are things that cannot be patented like laws of physics, theorems in mathematics, and material that is a subject for copyrights instead.
[1] I am not sure of this. There may or may not be specific legal criteria on this.
"Wait? I thought patents required a working prototype."
Not since 1880.
"If that's not the case I'm going to patent everything, but with quantum computers. And then everything, but with nanotechnology."
This is essentially what patent troll corporations do -- patent obvious mashups of New Technology X with Old Use Case Y. This sort of idea canvassing has been going on for a very long time.
You probably could, but you'd need pretty deep pockets to get decent coverage — it costs in excess of $1000 per patent. Filing dumb patents is a lot like a lottery.
