The quantum computer is something that bears watching. It can perform huge parallel searches and could bring a goodly slice of real time conversations within its mechanical ken. What exists now, probably too cumbersome and clumsy to watch anything close to what they would like to watch.
In 1998 when Clinton rescinded US export controls on cryptography my first thought was “Ah, sounds like NSA finally got their first quantum computer online”. We’ll probably not know for sure for another 50 years, but my guess is that’s not too far off the mark.