Good ref links. QC are very good at a small set of problems, that include the prime factorisation needed in PKC systems, such as Steem keys. Essentially QC are good at solving complex combinatorial problems. However, the hardware is currently very expensive and also prone to errors - the errors stem from the quantum states interacting with the environment, hence the core is cooled to below the temperature of outer space.

I think the most immediate threat comes from quantum computer simulators ;-)

$trendotoken