Extra explanation

From: Saibal Mitra <smitra.domain.name.hidden>
Date: Tue, 21 Apr 2009 15:29:52 +0200

I just send a posting to the FOR list about my article. I did not have the
time to reply to everyone on this list previously. Reading the old
discussion again, I think that it was suggested that the exact quantum
states matter, but they don't. It was only used to illustrate the thought
experiment by Deutsch which would allow one to prove that the MWI is

This is what I sent to the FOR list:

Some time ago I wrote a small article:


This was recently featured in New Scientist:


The idea is that an observer can undo things that have already happened by
resetting its memory, because when you reset your memory to a previous
state, that previous state you are evolving into will be the same in a
sector of the multiverse which evolved from that previous state and then was
reset for any reason. So, if the reseting is triggered for reason A or
reason B, it would lead to the observer ending up in the same state. The
outcome of a new measuremnt to find out why the mempory was reset is then
not pre-determined.

Some details:

The word "state" here refers to the classically describable state of an
observer. In the article, I focus on machine observers. The subjective state
of the observer is then exactly specified by specifying the ones and zeroes
of the bits of the memory. So, I assume that whatever the observer can be
aware of is encoded by the classical state of the bits of the computer and
not the exact quantum state of the computer. The exact state of the computer
has to be specified using a wavefunction of the computer (in fact, the state
of the computer will be entangled with the rest of the universe).

Then, one can write down any generic quantum state of the universe
containing the observer by supplementing the (classical) information stored
in the bits by the extra information you need to fully specify the
wavefunction of the computer and everything else in the universe. One can
then consider the unitary transformations that would represent a memory
backup, memory resetting etc.

After the memory resetting, you are notified why the memory was reset. Since
the relevant things happen in the realm where classical physics applies, the
probabilities are the same as what you would find using purely classical
reasoning. The interpretation of these probablilites is, however, different
from classical physics. When the memory is reset, you evolve to some state
while the rest of the inverse will be in some superposition of states in
which the memory was reset for various reasons. Then, before finding out why
the memory was reset, the outcome of that observation is not pre-determined

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Received on Tue Apr 21 2009 - 15:29:52 PDT

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