Yeah, quantum computers are indeed powerful computers that have the ability to potentially break the cryptography that Bitcoin uses, and this is something that can actually put people's Bitcoin at risk.
But some projects are actually working on using different kinds of cryptography that will be resistant to the power of the quantum computers. For example, some are actually looking in hash quantum cryptography or even other post quantum digital signature techs. If this is achieved, then the safety of crypto will be guaranteed, even with quantum computers around.