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From: George Levy <GLevy.domain.name.hidden>

Date: Thu, 27 Dec 2001 19:45:32 -0800

Thanks guys for the information. Now I have work on my hands.

George

Brent Meeker wrote

*>Do a search for "transactional quantum mechanics" and look at Vic Stenger's
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*>website.
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*>Brent Meeker
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scerir wrote:

*>
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*> > George Levy
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*> > This is interesting. Is it possible to transmit information from the
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*> > future to the past? If yes, how would this information be restricted?
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*>
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*> This is a very difficult issue, as you can see (example below).
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*>
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*> A single particle [the example is discussed in references 4, 2, 1]
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*> at time t_0 is (preselected) in the state
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*> |psi_0> = 3 ^ (-1/2) ( |a> + |b> + |c> )
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*> and at a later time t_f is (postselected)
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*> in the state |psi_f> = 3 ^ (-1/2) ( |a> + |b> - |c> )
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*> where |a>, |b> and |c> correspond to the particle being found
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*> in 3 boxes: A, B and C, respectively. (The N boxes case
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*> is discussed in reference 3.)
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*>
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*> At the intermediate time t_i, where t_0 < t_i < t_f,
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*> a measurement is performed on the system.
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*>
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*> The ABL rule [see reference 5] states that if a measurement
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*> is performed, at time t_i, on this system, with the above
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*> preselection and postselection of states, the probability
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*> for an outcome of either a or b (eigenvalues corresponding
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*> to find the particle in box A or in box B, respectively) is 100%.
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*>
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*> That is to say, the intermediate _measurement_ cannot project
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*> the initial state |psi_0> onto the state 2 ^ (-1/2) ( |b> + |c> ) --
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*> particle not found in A -- or onto the state 2 ^ (-1/2) ( |a> + |c> )
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*> -- particle not found in B --. That's because both states
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*> are othogonal to the final state |psi_f>. Both states are
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*> then impossible.
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*>
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*> As long as we keep the QM formalism and the ABL rule,
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*> in each case any particles (which end up postselected)
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*> are ones which could not have been in any box except
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*> the one which was opened, be it A or B.
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*>
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*> Possible solutions? There are some. In example....
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*>
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*> 1. QM formalism is right. There is no paradox. That's real.
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*>
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*> 2. QM formalism is right. That's not real. QM does not speak
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*> of reality.
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*>
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*> 3. Counterfactuals. To make a claim about the elements
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*> of reality of an individual system we have to consider the *physical*
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*> situation involved in an individual run of the experiment. But here,
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*> in each run, we have to make a *choice* to measure A or B.
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*> If we choose A, all postselected particles had to be found
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*> in box A. If we choose B, all postselected particles had to be found
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*> in box B. But the property of being, with certainty, in any one
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*> of those 2 boxes (depending on wich one is opened) cannot apply
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*> to the *same* *individual* particle in *any* given run of the
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*> experiment.
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*>
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*> 4. We cannot use the ABL rule here [see reference 6], because
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*> of the counterfactuals.
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*>
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*> Regards,
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*>
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*> -s.
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*>
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*> [1] David Z. Albert, Yakir Aharonov, Susan D'Amato,
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*> Physical Review Letters, vol. 54, pages 5 - 7,
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*> (1985)
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*>
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*> [2] David Z. Albert, Yakir Aharonov, Susan D'Amato,
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*> Physical Review Letters, vol. 56, p. 2457, (1986)
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*>
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*> [3] Yakir Aharonov, Lev Vaidman
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*> J. Phys, A-24, pages 2315 - 2328, (1991)
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*>
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*> [4] Lev Vaidman
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*> Foundations of Physics, 26, pages 895 - 906, (1996)
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*>
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*> [5] Yakir Aharonov, P.G. Begmann, J.L. Lebowitz,
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*> Physical Review, 134-B, pages 1410 - 1416, (1964)
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*>
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*> [6] R. E. Kastner
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*> Foundations of Physics, 29, pages 851 - 863, (1999)
*

Received on Thu Dec 27 2001 - 19:47:27 PST

Date: Thu, 27 Dec 2001 19:45:32 -0800

Thanks guys for the information. Now I have work on my hands.

George

Brent Meeker wrote

scerir wrote:

Received on Thu Dec 27 2001 - 19:47:27 PST

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