1: What is programming a quantum computer like?
2: What are the useful applications of a quantum computer?
I know everyone always says encryption, which implies that a quantum computer can run calculations in parallel; specifically, significantly more orders of magnitude more parallel than a conventional, multicore / multi-CPU computer.
But beyond that?
You compose a series of gates that manipulate the state qbits to perform calculation. My understanding is that these gates can be abstracted in a somewhat familiar programming language environment.
I've got a very rudimentary understanding, my crude summary would be: it's basically applied linear algebra, leveraging the properties of superposition to perform some types of computations more efficiently. Namely, reducing some search spaces to sqrt n.
This video is a good hands on intro: