X-Message-Number: 15041
Date: Tue, 28 Nov 2000 07:50:57 -0700
From: Mike Perry <>
Subject: Emulations on Turing Machines

Robert Ettinger, #15037, says

>For the computer to 
>reflect quantum reality (as presently understood by most physicists) or to 
>reflect Many Worlds, it would have to calculate ALL the possible successive 
>"states" and would therefore effectively grind to a halt immediately.

More correctly, the time requirements for the computer would grow
exponentially with those of the system it is calculating. In principle the
calculation could still be done, but in practice it would have to halt
rather quickly. (Presumably, though, a quantum computer could circumvent
this combinatorial bottleneck.)

>Note carefully that the Turing Machine ITSELF is CLASSICAL, even though it 
>can calculate quantum mechanics.
>So--once more--what do we have? The Turing Machine does not and CANNOT 
>emulate a person, because a real person does not always evolve into the next 
>most probable configuration.

There is no problem making the Turing machine (or a computer based on it)
probabilistic, so that in fact the less likely state changes will sometimes
occur, with expected frequencies. This could overcome any limitation on its
potential to emulate. (An interesting question is whether pseudorandomness,
rather than the real thing, would also be sufficient.)

Mike Perry

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