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.
The challenge here is that Quantum computers aren't even public yet for developers to start creating of some functions that can withstand any force. The Bitcoin hashing functions that are existing today didn't came from heaven, they were created after innovation of the internet and are use as part of Bitcoin cryptography, If tomorrow Quantum computers exist, there is going to be a kind of special cryptographic function that even Quantum computers can't break, it will need another special kind of computer.
However, the existence of Quantum computers is going to pose a big threat to Bitcoin. Not only Bitcoin though, any encryption that you can think of, Quantum computers are going to break it and that put even the government at risk, they will not allow it become a public tool because they are going to be affected the most. The nuclear weapons and all other dangerous weapons that are encrypted can be decrypted with a quantum computer which is not going to have a happy ending.