On Thu, Jun 09, 2005 at 04:09:15PM -0700, Norman Samish wrote:

> Does this mean that the quantum wave functions of all ten balls collapsed at 
> the moment we viewed the record and observed what happened to "6"?  Or did 
> the wave function never exist, since the robot's record always showed the 
> identity of the destroyed ball, irrespective of whether a human observed 
> this identity or not? 

In QM, it is not possible to distinguish featureless balls (systems in the
same quantum state). Storing labels in an external system (robot) would
perturb the systems, stopping them being featureless and/or precisely
localized. Experimental limitations currently prevent experiments with system
sizes much larger than a buckyball, IIRC.

If you're talking about entangling several such systems (qubits),
manipulating them by the robot should cause collapse of the total
wavefunction -- you need to do it in QC to be able to read the 
result. IANAP, though, so above may be wrong.

Eugen* Leitl <a href="http://leitl.org";>leitl</a>
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