X-Message-Number: 18490
Date: Tue, 05 Feb 2002 14:53:22 +0100
From: Henri Kluytmans <>
Subject: Re: Simulation, qubits

Yvan Bozzonetti wrote :

>Please note: We have a 2^813  states, each is a 813 bits word.

Indeed, if we had only 2^813 possible states...

>To simulate the Universe (ten billion light years in radius for ten billion 
>years) you need 10^244 Planck's cubes ( One Planck's unit for each dimension 
>in space and time). This could be run by a quantum computer with a 813 bits 
>word in a single computation cycle.

I could see this to be the case if, for example, only ONE Planck cube out 
of all 10^244 could be in the "on" state simultaneously for each overall
state (and all the other Planck cubes would then be in the "off" state). 

But this doesn't seem to be the case.

>This define a four dimensional classical universe. There is no storage 
>implied. After one computing round, everything is destroyed if there is no 
>coupling to a more long lived quantum state.  

And what would be that state you will be looking for ?

I.e. what would be the state(s) you want to let the quantum computer 
collapse into?

>What you write about, 2^(10^244), would define a simulation where each 
>instant of each elementary domain would interact with each other. This is a 
>world with time travel and multi stories: 

I agree, there are less than 10^244 qubits required. But certainly 
more than a mere 813.

For example, to factor a product of two primes with a combined size 
of 1000 bits. You will need at least a 1000 qubits. You will use 
the right quantum logic to let the qubits collapse into that single 
state that contains the two primes. There are 2^1000 possible 
combinations, but there is only 1 possible collapsed state.
The quantum logic will determine the collapsed state.

There are 2^(2^813) possible combinations when you have 
2^813 Planck cubes. Of course, because of time travel and 
other restrictions (e.g. the amount of matter, etc..) many 
possible combinations will not be allowed. At any certain 
point in time you have 10^183 Planck cubes. And again, not 
all possible combinations will or can occur. But that's usually 
what you use the quantum logic for : to filter out only certain 
allowed combinations by letting the system collapse. 


Please explain to me why precisely 2^813 out of all 2^(2^813) 
combinations remain ???

What kind of projection are you using ?

What kind of transformation is linking a 813 bits word to 
the state of the universe (i.e. the states of all 2^813 
Planck cubes).

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=18490