> Quantum computing Still gradually in development, presumably coming someday. It's very difficult to get quantum systems of any real complexity to not decoher

> Quantum computing Still gradually in development, presumably coming someday. It's very difficult to get quantum systems of any real complexity to not decohere before they can do useful computation. > DNA computing DNA-based storage apparently exists in the lab and might exist someday: http://arstechnica.com/information-technology/2016/04/microsoft-experiments-with-dna-storage-1000000000-tb-in-a-gram/ http://arstechnica.com/information-technology/2016/04/micros.... Current costs are something like $40 million/GB, so that'll have to come down "a bit". I don't know of anyone doing computation with DNA, biology seems too slow for that. > Optical computing It's very difficult to make light interact with other light (which is sine qua non for computation) except inside a material with electrons, where you get significant losses and there's no real advantage over just plain old transistors. Not likely to become a useful technology IMO.