[ExI] Reversible computing (Was: Re: ET Emergence (Was Re: Uploads as a group of AI agents))

[John Clark]

On Wed, Apr 1, 2026 at 4:54 AM Ben Zaiboc via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

*> Isn't reversible computing a bit like the Casimir Effect, a theoretical
> thing that /in theory/ could produce amazing benefits, but in practice, we
> will probably never be able to use?*
>

*Very small circuits that use logically reversible gates have been built
that operate on just a few bits of information, but it was enough to prove
that the theory is correct because they beat any irreversible computer when
it comes to energy usage because they didn't need to erase any information,
Landauer’s Limit says that the minimum amount of energy needed to erase one
bit of information is  kT ln 2. The downside of those experimental
reversible computers is that although they use less energy they also
require more complex circuitry and they are much slower than conventional
computers. *

*A perfect quantum computer would be a reversible computer but such a thing
is probably impossible, a real quantum computer would need error correction
and that is irreversible. Drexler style Nanomachines can also be reversible
but when designing them you need to take the Casimir Effect into account
because it can be a problem; the force of attraction is inversely
proportional to the distance to the fourth power so it grabs on fast as the
distance between parts shrinks. Casimir attraction can also be helpful if
you want a part in your nanomachine to have something that behaves like a
spring.  *

*With careful design the Casimir force can be shaped, for example if you
use a dielectric material instead of a conductive metal the attraction is
greatly reduced,  and if you put a fluid with carefully designed dielectric
properties between the plates you can even get a force of repulsion instead
of attraction. You could use Casimir to keep two parts in your nanomachine
precisely aligned without contact, and then you could make a no contact no
wear bearing that would operate similar to the way magnetic levitation does
but by using quantum vacuum forces instead of magnetism.*


*John K Clark*


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