Even a general purpose quantom computer would be hard/impossible to verify without studying the internals. For example, we have used a general quantom computer

Even a general purpose quantom computer would be hard/impossible to verify without studying the internals. For example, we have used a general quantom computer to preform shors algorithm and factor 21. I am not aware of how long the computer took to do so, but it would not suprise me if my cellphone would be faster using naive trial division.