Forgive my ignorance but haven't there been experiments that prove quantum theory? Why all the fuss about quantum computers if its just a pie in the sky hypothe

Forgive my ignorance but haven't there been experiments that prove quantum theory? Why all the fuss about quantum computers if its just a pie in the sky hypothesis? (It's not a field I am familiar with other than on a very superficial level, so an "explain it like I'm 5" would be most useful in responses to my points).