>> But for anyone who wonders why I’ve been obsessing for years about the need to design efficiently verifiable near-term quantum supremacy experiments: well, this is why! We’re now deeply into the unverifiable regime that I warned about.

Can anybody explain me why it is hard to find a problem that can be solved only by a basic quantum computer within a short timespan and can be easily verified by a normal computer? I thought there are so many algo's out there for which one direction is fast and the reverse takes ages.