NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/sci/physics/21672

Internet Message Format | 1992-12-23 | 3.5 KB

Path: sparky!uunet!mtnmath!paul
From: [e-mail] (Paul Budnik)
Newsgroups: sci.physics
Subject: Re: PS on Budnik's "delay" in Bell's inequality test.
Message-ID: <[e-mail]>
Date: 23 Dec 92 16:11:48 GMT
References: <[e-mail]> <[e-mail]>
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070
Lines: 55

In article <[e-mail]>, [e-mail] (Bronis Vidugiris) writes:
> In article <[e-mail]> [e-mail] (Jack Sarfatti) writes:
> )
> )I looked again trying to understand what is exciting Budnik so much. Does he
> )not know that Aspect's experiment in 1982 has polarization orientation
> )switching times that were short compared to photon flight times from source
> )to detectors. So that the nonlocal correlation of (cos@)^2/2 that violates
> )Bell's locality inequality is definitely observed across spacelike
> )intervals.

This is not correct. There was no *direct* measurement in Aspect's
experiment of the delay between when a particle traversed the polarizer
and was detected. Aspect estimated delays based on assumptions about
flight time. Such assumptions are not in general valid in QM.
You cannot know where a particle is at a given time unless you observe
the particle at that time. See J. D. Franson, Physical Review D, pgs.
2529-2532, Vol. 31, No. 10, May 1985 for a detailed analysis of this
issue.

> )If that is his concern then the answer is simple. But it seems to
> )be something else- he says the "delay" can be measured but he does not give
> )a clear and complete procedure so that I conclude it is much ado about
> )nothing. I would like to be proved wrong in this opinion if any one else
> )thinks they understand Budnik's idea.

The way you measure the delay is by varying the polarizers between states
that maximize and minimize the probability of joint detections. You
then directly measure the time delays between when you have changed the
polarizers and when this affects the probability of a joint detection.
This is a technically more difficult experiment than Aspect's. Since
you cannot control when a photon traverses the polarizer the delays will
be dominated by the lack of synchronization between when a photon is emitted
and when a polarizer changes state. You can minimize this by emitting
photons at a rapid rate, but the rate cannot be too high or you will not
be able to distinguish joint detections from the detection of two photons
from different photon pairs. These problems can be dealt with by increasing
the total distance between the photon source and detectors. This introduces
additional technical problems. I do not know how difficult such an experiment
would be, but it is certainly doable in theory. That is all this is needed
to prove my claim that quantum mechanics is an incomplete theory.

> I'm curious too - I checked and I don't have ready access to the reference
> Paul cites and I haven't followed up 'special ordering' it from our library.
>
> One concern I had in thinking back over the experiment was the delay between
> the emission of the cascade photons.  [I assume Aspect used cascade
> photons.]

Aspect measured the times between joint detections and depended on the
geometry of the experiment and the flight time of photons to estimate the
delays. Franson argued that this was not legitimate. The delays could have
been as long as the excited states of the atom emitting the photon or
even as long as the coherence times of the lasers used to excite the atoms.

Paul Budnik