Let me avoid the technical aspects to make things easy for all readers.
So someone said that America's NSA has this great computer(quantum computer) that could easily hack Bitcoin private keys. I really doubt his claim but I know for sure that certain computers like the most powerful Super Computers are within the reach of some of this Intelligence organizations.
Do you think such computers can crack any security codes put in place to make Bitcoin very secure?
No! It's as simple as that. Firstly the Super Computer was not built yesterday, it's been there since a long time now, and if it could not attack it in its inception days, then it cannot do so now, that it's grown even stronger and better. The technology may be hacked, but Bitcoins never. Have you ever heard of them being hacked, I don't think I have heard so far or else no one would ever use them.