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This regards an article found in the journal of Nature, 26 Aug. '04. I thought it might be interesting, not so much for the physics it presents (although they are certainly fascinating) but because of the implications. I think a discussion around the questions provided at the end of this essay might be interesting.
From the journal of Nature, 26 Aug. '04 (By Seth Lloyd, Dept of Mechanical Engineering, MIT):
The article then goes on to discuss "logically reversible operations" such as NOT and "logically irreversible operations" such as ERASE which requires physical irreversibility implying increasing entropy.
Also:
They discuss quantum computers but I gather that still, erasing or generation of errors in the data results in an increase in entropy.
The last paragraph seems to beg one's imagination, so perhaps some discussion about what the implications are would be of interest.
So... is it possible that computations can be performed forever? Does this imply anything about physical reality?
(I can email the article to anyone interested in reading it if you PM me, but it is too large to upload.)
From the journal of Nature, 26 Aug. '04 (By Seth Lloyd, Dept of Mechanical Engineering, MIT):
There are some processes that are effectively reversible: no energy is dissipated, and entropy remains constant, or almost so. Chemical reactions are reversible if run sufficiently slowly; they can dissipate arbitrarily small amounts of energy per step. Coherent quantum-mechanical processes such as tunnelling and superconductivity are reversible and can operate without dissipation. And so can computation, in principal.
The article then goes on to discuss "logically reversible operations" such as NOT and "logically irreversible operations" such as ERASE which requires physical irreversibility implying increasing entropy.
But then Charles Bennett and independently, Ed Fredkin realized that most logically irreversible operations can be embedded in slightly more complicated reversible operations. As a consequence, computation can in principal be implemented using reversible physical processes ... The one logically irreversible process that connot be embedded in a more complicated reversible process is erasure: when you erase the last copy of a bit from your computer, entropy must increase elsewhere.
Also:
Quantum computers are the closest thing we have to devices that carry out computation in a logically and physically reversible fashion.
They discuss quantum computers but I gather that still, erasing or generation of errors in the data results in an increase in entropy.
The last paragraph seems to beg one's imagination, so perhaps some discussion about what the implications are would be of interest.
What about death? Must computation, like all physical processes, grind to a close? In fact, as long as the expansion of the universe keeps supplying free energy and environment into which to reject errors, the known laws of physics apparently allow a computer to compute for ever. Just what might an eternal computer compute? The answer will have to wait.
So... is it possible that computations can be performed forever? Does this imply anything about physical reality?
(I can email the article to anyone interested in reading it if you PM me, but it is too large to upload.)