Is quantum computer a threat?

I sincerely wonder how dangerous the development of the quantum computer really is. Is it really a threat to the blockchain and the Bitcoin network?
I'm trying to understand but I'm finding contradictory information on the subject.
Can Bitcoin ward off this threat? If the threat exists, of course.
What will all investors do if it's really a threat?
As far as I understood, there are some Blockchain who can resist to quantum but it's not the case with Bitcoin, right ?
I'd really appreciate it if someone with more technical knowledge than me could explain the quantum computer problem to me.