Via Next Big Future, Doctor Suzanne Gildert of the excellently-named Physics & Cake blog takes apart the [science fictional / Singularitarian] concept of computronium, and does a pretty good job of explaining why it probably isn’t possible:

… as we see, atoms are already very busy computing things. In fact, you can think of the Universe as computing itself. So in a way, matter is already computronium, because it is very efficiently computing itself. [This reminds me of Rudy Rucker’s theories about gnarl and universe-as-computing-substrate – PGR] But we don’t really want matter to do just that. We want it to compute the things that WE care about (like the probability of a particular stock going up in value in the next few days). But in order to make the Universe compute the things that we care about, we find that there is an overhead – a price to pay for making matter do something different from what it is meant to do. Or, to give a complementary way of thinking about this: The closer your computation is to what the original piece of matter would do naturally, the more efficient it will be.

So in conclusion, we find that we always have to cajole matter into computing the things we care about. We must invest extra resources and energy into the computation. We find that the best way to arranging computing elements depends upon what we want them to do. There is no magic ‘arrangement of matter’ which is all things to all people, no fabled ‘computronium’. We have to configure the matter in different ways to do different tasks, and the most efficient configuration varies vastly from task to task.

If it’s not too meta a get-out clause, perhaps we could develop some sort of nanotech system for reconfiguring computational substrate matter into the most appropriate arrangement for the task at hand? Talk about an abstraction layer… 🙂