There are plenty of dual-use technologies. That is, one’s that have both a private sector and military application. The big secret agencies rarely keep these things to themselves. The economic advantages of QC are too great to just sit on.

Isn’t post-quantum cryptography already a thing? Probably not implemented in anything meaningful yet, but still.

Unfortunately for them, most of the progress is coming from the private sector (like most cutting edge tech these days) and those guys like to brag too much to let NSA come in and say “hey can we use that on the dl for about 3 years before you say anything”