RE: Reversible computing

From: David Barrett-Lennard <>
Date: Thu, 13 Nov 2003 10:14:08 +0800

Assuming neurons aren't able to tap into QM stuff because of
decoherence, it seems odd that consciousness is performed with an
irreversible computation whilst the universe uses a reversible

- David

-----Original Message-----
From: Russell Standish []
Sent: Thursday, 13 November 2003 9:59 AM
To: David Barrett-Lennard
Subject: Re: Reversible computing

I think the answer to your question is yes (assuming I understand you
correctly). Information and probability are closely linked (through
algorithmic information theory - AIT for those acronym
lists). Schroedinger's equation is known to conserve probability
(basically |\psi(t)| is a constant - usually set to 1 - under
evolution by Schroedinger's equation (|.| here means Hilbert spoace
norm, not
absolute value)). This conservation of probability turns out to be
equivalent to unitarity of the Hamiltonian operator, which guess what,
means energy is conserved.

Unitary evolution is a reversible computation, which is why quantum
computations are reversible.


David Barrett-Lennard wrote:
> I have been wondering whether there is something significant in the
> that our laws of physics are mostly time symmetric, and we have a law
> conservation of mass/energy. Does this suggest that our universe is
> associated with a reversible (and information preserving) computation?

> - David

A/Prof Russell Standish            	 Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119
UNSW SYDNEY 2052                     	 Fax   9385 6965, 0425 253119
Room 2075, Red Centre
            International prefix  +612, Interstate prefix 02
Received on Wed Nov 12 2003 - 21:16:17 PST

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