Personal quantum computers would be truely useless. They break specific kinds of encryption, and simulate other quantum systems. Other than that, nobody's been able to devise a way to make them do much practical work.
Really, it's unfortunate they were named that, because they're only like computers if you have a solid background in computing to understand the analogy. "Quantum emulator" or "programmable quantum system" might be a better word that wouldn't make people think it's the next semiconductor node. Alas, I have no time machine to fix it.
Maybe useless to you. I’ll definitely find use for it. And cracking encryption is a huge plus. Quantum computers have been around for a long time and in use there are all sorts of software and even special OS for it just not for public use for obvious reasons.
Bro, do you even know a Kronecker product from a discrete log? You'll find a use my ass. And now you're in with a super secret group of quantum computer users. Are you sending ninjas after me next?