Also, did anyone mention the connection between reversable computers and
cooling? In some of these circuits, you have to feed known values--
strings of zeroes--into some inputs (corresponding to coolant), and
you get essentially noise bits on some outputs (corresponding to waste
heat). But the "bits" in some physical models of gates are just different
movement states of molecules, so I always thought the analogy ought to
work backwards.
In other words, you would shift molecules in a known state into contact
with the thing you wanted to cool, it would interact with them, and you
would shift the perturbed molecules away. Better yet would be a way
to transfer the changed state along a string of unmoving molecules,
say by something like lasing, where one molecule would drop back to its
lowest energy state, releasing a photon or phonon, and putting the next
molecule in the high energy state, all in a clocked, directed way...
Seth Lloyd has cool designs for molecular computers made out of regular
crystals, where light pulses from outside prompt interactions between
neighboring (groups of) atoms in the lattice. If you have molecules of
three types in a row, like ABCABCABC..., the different reactions are sort
of catalized by different frequencies of light, so you can trigger AB
reactions, then BC, then CA, etc., and you have a shift register.
I think any refrigerator is limited by how finely it can
distinguish and carry away information about different states of the thing
it's cooling.
--Steve
-- sw@tiac.net http://www.tiac.net/users/sw "It just keeps going and going and therefore you yourself have to keep going and going." --Energizer Bunny researcher