I skimmed the paper. It looks like gate size grows as the square of the number of bits. I was unable to tell how the size of the "multimode memory" scales with

I skimmed the paper. It looks like gate size grows as the square of the number of bits. I was unable to tell how the size of the "multimode memory" scales with the problem size, but that could just be a problem with how quickly I skimmed. Anyway, practical multimode memory doesn't seem to have been built at any scale, based on some cursory googling.