>mechanical logic (which works by moving around baryons) can scale down further than electronic logic, which is already running into Heisenberg problems with current semiconductor fabrication technology.
I think I must be missing something here, I thought this was working with atoms. Are you saying that someday mechanical logic could be made to work inside the nucleus? Seems like you might be limited to ~200 nucleons per atom, and then you'd have to transmit whatever data you computed outside the nucleus to the nucleus in the next atom over? Or are we talking about converting neutron stars into computing devices? Do you have a good source for further reading?
No, no, not at all! That kind of thing is very speculative, and I don't think anybody knows very much about it. What I'm saying is that the position of a nucleus is very, very much more precisely measurable than the position of an electron, so it has a much weaker tendency to tunnel to places you don't want it to be, causing computation errors. That allows you to store more bits in a given volume, and possibly do more computation in a given volume, if the entropy production mechanisms can be tamed.
We routinely force electrons to tunnel through about ten nanometers of silicon dioxide to write to Flash memory (Fowler–Nordheim tunneling) using only on the order of 10–20 volts. That's about 60 atoms' worth of glass, and the position of each of those atoms is nailed down to only a tiny fraction of its bond length. So you can see that the positional uncertainty of the electrons is three or four orders of magnitude larger than the positional uncertainty of the atomic nuclei.
I think I must be missing something here, I thought this was working with atoms. Are you saying that someday mechanical logic could be made to work inside the nucleus? Seems like you might be limited to ~200 nucleons per atom, and then you'd have to transmit whatever data you computed outside the nucleus to the nucleus in the next atom over? Or are we talking about converting neutron stars into computing devices? Do you have a good source for further reading?