From: scerir (scerir@libero.it)
Date: Fri Sep 20 2002 - 02:10:48 MDT
Lee Corbin
> Well, I would say that in *any* QM an instantaneous transfer
> of information is impossible. But maybe there are bizarre
> theories...
A. Valentini ["Signal-Locality, Uncertainty, and the Subquantum
H-Theorem", Physics Letters, A-156 p. 5 and A-158 p.1] has given
an insightful discussion of the possibility of superluminal signaling
within the framework of Bohm's quantum mechanics.
Bohmian Mechanics is equivalent to QM only as long as
Prob = |psi|^2 and only as long as uncertainty relations are satisfied.
In general that's not true in there.
> > But in standard QM it *is* possible to 'teleport' some
> > 'information' (actually a quantum state, unknown too)
> > by exploiting EPR correlations, i.e. two entangled particles.
> I think that you should use "influence", not information.
> Otherwise, it directly contradicts your very first sentence
> above.
No, 'information' is the word. Because teleportation needs
also a classical channel, between Alice and Bob. Hence
no FTL messages are allowed.
> > which can also be written as
> > |1,2, one> * (-a |+,3> - b |-,3>) +
> > |1,2, two> * (-a |+,3> + b |-,3>) +
> > |1,2,three> * (a |-,3> + b |+,3>) +
> > |1,2, four> * (a |-,3> - b |+,3>)
> What are "one", "two", "three", and "four"?
Those are called Bell states, a convenient (complete
orthonormal) basis (of Hilbert spaces) in which to
represent two particles entangled states.
> I think that
> you have factored out the |+,3> and |-,3>
Yes, the calculation is boring, and long, nothing special.
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