There is one possible downside to having a superfast quantum computer such as the one envisioned by Nobel Prizewinners Serge Haroche and David J. Wineland. Right now, your secure websites are protected by passwords that, for the present level of technology, are good enough to avoid cracking by other PCs.
But what if a strong password such as recommended by Microsoft isn’t good enough for a supercomputer that is thousands of times faster than the fastest PCs? In that case, if the hacker has access to one of these quantum computers, even a strong password may not be enough. Perhaps the next step is what Bank of America is doing right now: namely, asking you a question whose answer has been predetermined by you and requiring a strong password as well. Perhaps some websites may ask you a whole string of questions.
Eventually, keeping tabs on a whole plethora of passwords will become a far more tricky task than it is now. There may be whole strings of passwords which are too complicated to be remembered directly by any human. What to do? You can perhaps put them in an Excel file on your computer which is itself passworded,
In any case, as usual, the more things advance, the more complicated they become.