Re: copy method important?

From: Saibal Mitra <>
Date: Sat, 18 Jun 2005 22:35:22 +0200

You ca still create two identical systems starting from another system. E.g.
in stimulated emission two photons are created in the same state. Another
example is a Bose Einstein condensate, in which all the atoms are in the
same state.

Note that you can still teleport an unknown quantum state despite
Heisenberg's uncertainty principle (you do this without measuring the
state). It can be shown that you can't copy an unknown quantum state,
because that would violate the Schrodinger equation.

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----- Original Message -----
From: "Norman Samish" <>
To: <>
Sent: Saturday, June 18, 2005 08:36 PM
Subject: Re: copy method important?

> I'm no physicist, but doesn't Heisenberg's Uncertainty Principle forbid
> making exact quantum-level measurements, hence exact copies? If so, then
> all this talk of making exact copies is fantasy.
> Norman Samish
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ----- Original Message -----
> From: "rmiller" <>
> To: "Stathis Papaioannou" <>;
> <>; <>
> Sent: Saturday, June 18, 2005 10:05 AM
> Subject: copy method important?
> All,
> Though we're not discussing entanglement per se, some of these examples
> surely meet the criteria. So, my thought question for the day: is the
> method of copying important?
> Example #1: we start with a single marble, A. Then, we magically
> create a copy, marble B--perfectly like marble B in every way. . .that is,
> the atoms are configured similarly, the interaction environment is the
> same--and they are indistinguishable from one another.
> Example #2: we start with a single marble A. Then, instead of
> magically creating a copy, we search the universe, Tegmarkian-style, and
> locate a second marble, B that is perfectly equivalent to our original
> marble A. All tests both magically avoid QM decoherence problems and show
> that our newfound marble is, in fact, indistinguishable in every way from
> our original.
> Here's the question: Are the properties of the *relationship*
> between Marbles A and B in Example #1 perfectly equivalent to those in
> Example #2?
> If the criteria involves simply analysis of configurations at a
> precise point in time, it would seem the answer must be "yes." On the
> other hand, if the method by which the marbles were created is crucial to
> the present configuration, then the answer would be "no."
> R. Miller
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Received on Sat Jun 18 2005 - 16:36:36 PDT

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