NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/sci/physics/21825

Internet Message Format | 1992-12-28 | 9.1 KB

Xref: sparky sci.physics:21825 alt.sci.physics.new-theories:2632
Path: sparky!uunet!mtnmath!paul
From: [e-mail] (Paul Budnik)
Newsgroups: sci.physics,alt.sci.physics.new-theories
Subject: Aspect's experiment, was Re: Peer review ...
Message-ID: <[e-mail]>
Date: 28 Dec 92 21:19:33 GMT
References: <[e-mail]>
Followup-To: sci.physics
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070
Lines: 188


    Arguing with Jack Sarfatti is a bit like shoveling manure in a barn
full of horses. No matter how much you shovel today there will be just
as much to shovel tomorrow. It is not that Jack is unintelligent or does
not know physics. It is just that he is extremely careless. He seems to
confuse lack of scientific discipline with scientific adventurousness.
They are not the same thing. Scientific adventurousness is impossible
without scientific discipline.

    It is nonetheless sometimes useful to respond to him, because he
raises issues that others may also be confused about.

In article <[e-mail]>, [e-mail] (Jack Sarfatti) writes:
> > I do not what Aspect thinks but the two references that I am relying on
> > are:
> > J. D. Franson, Physical Review D, pgs. 2529-2532, Vol. 31, No. 10, May
> > 1985.
> > A. Leggett, Foundations of Physics, V 17, p. 875.
>
> *OK, Paul, good. Since I do not have easy access to these references, and
> since others interested in the truth here may not, please take the time to
> type it relevant quotes from Franson and Leggett that you think explain,
> clarify, and support your point - a point that, so far, evades me since
> your idea about "delay" is like Merlin's many changing forms.*

I have previously posted some quotes and have included them at the end
of this article. I suspect it is your careless reading and not my definition
of delay that is responsible for the `many changing forms'.

> > Both make it clear that Aspect's experiment was not conclusive.
>
> *But do they make it clear in your one sense of "dely" that I thought I
> understood, namely, the delay in the photon passing from a polarizer to a
> detector - then you changed it in midstream to the uncertainty in the time
> of emission at the source - so anyone trying to follow you will be totally
> confused!*

If you had read my article carefully you would have understood that I only
introduced the issue of the uncertainty in emission time because it was
relevant to how accurately you can measure the critical delay. The critical
delay is the time between when you change polarizer angles and this has
an observable effect on joint detections.

> > I am not aware of any refutation of the arguments these two present. I have
> >  read
> > Aspect's original papers and I think the arguments that Franson and Leggett
> > make are correct.
>
> *What the hell are their arguments? And how do thir arguments connect with
> whatever it is you are trying to say?*

Their arguments are that Aspect did not directly measure the critical delay
I just described and his experiment did not put a tight enough constraint on
this delay to prove that locality was violated.

>
> > [...]
> > In my analysis this delay is negligible (i.e. short compared to flight
> > times from source to polarizer) and essentially irrelevant. Why do you
> > think it important?
>
> Unless you measure it directly you have no proof that locality is violated.
>
> *Paul , I do not understand your point here at all. Can you draw a picture?
> Can anyone else reading this explain what Paul means?

I do not know what could be clearer. To prove Bell's inequality is violated
you must show that changing the polarizer angles produces a change
in correlation values as predicted by QM and that these two events, the
change in polarizer angles and the resulting change in joint detections
have a space-like separation. The only way to do this is to measure the
times and distances between these events.

>[...]
> It is also central to my argument that QM is incomplete. You can measure
> the
> statistics of these delays, but QM does not predict what those statistics
> are.
>
> *Paul, I still do not understand which delays you are talking about and how
> you would measure them in principle - you must be much more specific !*

I do not know what could be simpler. You change polarizer angles and you
measure the time it takes for this change to have an observable effect.
Doing this with enough accuracy is not simple, but conceptually what
you need to do is very simple.

>[...]
> > You cannot know what any of the times are that you discuss.
>
> *Fine, Paul, I agree that in the actual experiment done by Aspect that you
> cannot know those times. But, that is not the point, the point is you do
> not need to know them! And if you did need to know them, it would be a
> different experiment! Why do you want to know them? Aspect was trying to
> measure (cos@)^2/2 - or, rather, the deviation from it predicted by Bell's
> locality inequality - and his curves are quite beautiful - and the
> correlation is over a spacelike interval between detections of both photons
> in same pair - that's all that matters.*

Aspect showed that the joint detections had a space-like separation. This is
*irrelevant* to the question of whether Bell's inequality is violated.
The events that must be space-like separated are the changes in polarizer
angles and the resulting effects on joint detections. Aspect estimated
this delay based on flight time. This is not a legitimate thing to do
in QM the way it is in classical mechanics.

>[...]
> *As Ronald Reagan would say "There you go again Paul!"  I thought we agreed
> that Aspect did not measure, or need to measure (well maybe we do not agree
> on the need part) the delays from polarizer to detector for each photon in
> the pair - who gives a damn?

The measurements are of *macroscopic events* not of photon
positions. The critical measurement is the delay between when a polarizer
changes angles and this has an observable effect. This must be measured
directly. One cannot make estimates based on assumptions about what is
happening at a microscopic level. After all the point of this experiment is to
test the correctness of QM itself. Thus you should not assume QM in analyzing
these experiments. Even if you assume QM you still do not when the
particles traversed the polarizers because you cannot know in QM where
a particle is at a given time unless you observe it *at that time*.

> *Yeah, Paul - but what does that mean operationally- what do you actually
> do -I mean in principle what would you try to have done? You are still
> being very vague - what does "between states" mean, for example?*

I repeat what can be simpler then changing polarizer angles and seeing
how long it takes for this to effect joint detections.

>[...]
> *But the point is, to get good measurements, you want to pulse the emission
> of the pairs so that no photons are in the polarizer during the time the
> orientation is changing.

You do not need to this and cannot do this because you have no idea when
the photon is `in the polarizer'.

> Or you want to do it so fast that the noise
> introduced is very small compared to what you are looking for.

This is a constraint.

> Also these
> delays are not what Bell's inequality is all about - [...]

On the contrary they are precisely what Bell's inequality is about.

Paul Budnik

_______________

Anthony Leggett observed in a review of several books including
"Quantum Reality" by Nick Herbert:

    The one point on which I believe Herbert seriously misleads the reader
    is his repeated and emphatic statements on pp. 230-235 that Bell's
    theorem, and the related experimental results requires superluminal
    responses at the $macroscopic$ level ...

    No it doesn't --- not if the word "macroscopic" has anything remotely
    resembling its everyday use and we stick rigorously to experiments
    which have actually been done rather than extrapolating their results
    according to our theoretical prejudices.
    ... if we look in detail at the geometry of the
    experiments, the lifetime of the intermediate atomic state,...,
    we see that even in the latest (Aspect) experiments ... the
    "macroscopic"(?) events ..., or at least an appreciable fraction
    of them, $were probably never separated by a space-like interval$ ...

    [Foundations of Physics, V 17, p. 875]

Franson in discussing how long the delay might have been in Aspect's
experiment between when a polarizer angle changed and this had an effect
notes:

    The time interval over which the probability amplitude discussed
    above may simultaneously exist and interact in the experiment by
    Aspect, Dalibard, and Roger could conceivably be comparable to
    the 89-nsec lifetime[12] of the excited atomic state which produces
    the pair of photons. If the photon emission time remains indeterminate
    for this length of time, then it is plausible that the final outcome
    of the event may remain indeterminate for a comparable amount of time.

Franson goes on to suggest that it might even be indeterminate for the
coherence time of the lasers used to excite the photon source. These
times are long enough to allow local effects to produce the correlations
Aspect observed.