RE: Quantum Rebel
I had a typo and was confusing about the 50/50 likelihood below.
Corrections in CAPS.
The interference pattern is of the form:
Interference field = [cos(ax)+i*0.8sin(ax)]exp(ibZ-iwt)
If Beam A and Beam B had EQUAL amplitudes, you would maximize the
uncertainty of the photon origin since you have to say 50/50 likelihood
for a photon coming from either A or B.
-Original Message-
From: Russell Standish [mailto:[EMAIL PROTECTED]
Sent: Saturday, August 14, 2004 2:51 AM
To: Fred Chen
Cc: 'Everything List'
Subject: Re: Quantum Rebel
On Fri, Aug 13, 2004 at 11:43:10PM -0700, Fred Chen wrote:
...
>
> A better (and far simpler) way to challenge complementarity would be
> to use a low-intensity interferogram in a photographic film or CCD. At
> first the photons being detected are few so the shot (particle-like)
> aspect is more obvious. As more photons are integrated, the classical
> interference pattern is observed. Can there be a transition region
> where both aspects are observable?
>
This does not challenge complementarity. Consider a double slit
apparatus with the photon source's intensity down so low that each
individual photon can be observed hitting the screen one at a time. But
when one plots the distribution of positions where the photons strike
the screen after observing many of them, the interference pattern
results. This is simple and uncomplicated, but is not what the
complementarity principle is about.
Now consider that you have information about which slit the photon
passed through before hitting the screen - ie each photon is labelled 1,
2, 1, 1, etc, according to whuch slit it passed through. Therefore, you
can separate the observed photons into two sets, according to which slit
the phtons passed through. The distribution of each subset corresponds
to a single slit experiment, and the final distribution must be the sum
of the two single slit experiements. But single slit experiments do not
have interference patterns - hence the sum cannot have an interference
pattern either.
Consequently, if you have any way of knowing which slit the photon went
through (the "which way" information), then you cannot have an
interference pattern. This is what the complementarity principle means.
Cheers
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a virus.
It is an electronic signature, that may be used to verify this email
came from me if you have PGP or GPG installed. Otherwise, you may safely
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A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119
(mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119
(")
Australia[EMAIL PROTECTED]
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International prefix +612, Interstate prefix 02
Re: Quantum Rebel
I do not know how complementarity is applied to this scenario - anyone
else have a suggestion?
On Sat, Aug 14, 2004 at 04:56:12PM -0700, Fred Chen wrote:
> Russell, I agree with what you state below. But consider the following
> experiment.
>
> Instead of two beams of equal intensity interfering, as in classical
> inteferometry, one has unequal amplitude beams. Specifically,
>
> Beam A: 0.9*exp(iax+ibz-iwt)
> Beam B: 0.1*exp(-iax+ibz-iwt)
>
> The interference pattern is of the form:
>
> Interference field = [cos(ax)+i*0.8sin(ax)]exp(ibx-iwt)
>
> So the resulting photon distribution follows the intensity, or the field
> amplitude squared:
>
> Interference intensity = 0.64+ 0.36*cos^2(ax)
>
> This wave pattern will begin to appear after sufficient number of
> photons, but each photon is always ~99% (81/82) likely to have
> originated from Beam A, based on conservation.
>
> If Beam A and Beam B had different amplitudes, you would maximize the
> uncertainty of the photon origin since you have to say 50/50 likelihood
> for a photon coming from either A or B.
>
> The complementarity principle's strongest statement is 100% certainty,
> and that cannot be attained. But we can still get an idea of the wave
> interference pattern and 'which way' information with high (but not
> 100%) certainty in gray-transition cases such as above.
>
> Fred
>
> -Original Message-
> From: Russell Standish [mailto:[EMAIL PROTECTED]
> Sent: Saturday, August 14, 2004 2:51 AM
> To: Fred Chen
> Cc: 'Everything List'
> Subject: Re: Quantum Rebel
>
>
> On Fri, Aug 13, 2004 at 11:43:10PM -0700, Fred Chen wrote:
> ...
>
> >
> > A better (and far simpler) way to challenge complementarity would be
> > to use a low-intensity interferogram in a photographic film or CCD. At
>
> > first the photons being detected are few so the shot (particle-like)
> > aspect is more obvious. As more photons are integrated, the classical
> > interference pattern is observed. Can there be a transition region
> > where both aspects are observable?
> >
>
> This does not challenge complementarity. Consider a double slit
> apparatus with the photon source's intensity down so low that each
> individual photon can be observed hitting the screen one at a time. But
> when one plots the distribution of positions where the photons strike
> the screen after observing many of them, the interference pattern
> results. This is simple and uncomplicated, but is not what the
> complementarity principle is about.
>
> Now consider that you have information about which slit the photon
> passed through before hitting the screen - ie each photon is labelled 1,
> 2, 1, 1, etc, according to whuch slit it passed through. Therefore, you
> can separate the observed photons into two sets, according to which slit
> the phtons passed through. The distribution of each subset corresponds
> to a single slit experiment, and the final distribution must be the sum
> of the two single slit experiements. But single slit experiments do not
> have interference patterns - hence the sum cannot have an interference
> pattern either.
>
> Consequently, if you have any way of knowing which slit the photon went
> through (the "which way" information), then you cannot have an
> interference pattern. This is what the complementarity principle means.
>
> Cheers
> --
> *PS: A number of people ask me about the attachment to my email, which
> is of type "application/pgp-signature". Don't worry, it is not a virus.
> It is an electronic signature, that may be used to verify this email
> came from me if you have PGP or GPG installed. Otherwise, you may safely
> ignore this attachment.
>
>
>
> A/Prof Russell StandishDirector
> High Performance Computing Support Unit, Phone 9385 6967, 8308 3119
> (mobile)
> UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119
> (")
> Australia [EMAIL PROTECTED]
>
> Room 2075, Red Centre
> http://parallel.hpc.unsw.edu.au/rks
> International prefix +612, Interstate prefix 02
>
>
>
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
Re: Quantum Rebel - complementarity
As I had mentioned in a previous post, complementarity doesn't even
crack a mention in the textbook I learnt QM from (Shankar's book). I
found it in another textbook I had (Schiff's book), which describes it
as being a another way of expressing Heisenberg's uncertainty
princple. I'm not even sure that's true, and in any case I believe
Shankar's book to be superior of the two.
When I thought about it, I realised what complementarity refers in the
double slit experiment - this is what I've been discussing. I'm not at
all certain how it applies in other contexts, however.
Cheers
On Sat, Aug 14, 2004 at 09:58:10AM -0400, John M wrote:
> Dear Russell,
>
> I really would like to read (if ever) about that darn complementarity -
> based on/around a different example from the stale double-slit experiment
> (which it was really constructed for).
>
> IMO the 'double' nature of particle-wave is not (well?) understood and this
> resulted in sweating out the 'complementarity' syndrome to explain some
> hard-to-follow experimental results within the ongoing formalism. (I mean to
> match the quantized items within the system).
>
> Since 2x10^m million experiments - calculations and 3x10^n papers (not to
> speak about hundreds of prizes, tenthousands of tenure) have been devoted to
> the concept - taught to 3 consecutive generations of
> young receptive brains, it would be a BIG job to reformulate it.
>
> Yet it would be refreshing to approach the concept from another side
> (another framework), - maybe a new one??
>
> John Mikes
>
> - Original Message -
> From: "Russell Standish" <[EMAIL PROTECTED]>
> To: "Fred Chen" <[EMAIL PROTECTED]>
> Cc: "'Everything List'" <[EMAIL PROTECTED]>
> Sent: Saturday, August 14, 2004 5:50 AM
> Subject: Re: Quantum Rebel
>
>
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Australia[EMAIL PROTECTED]
Room 2075, Red Centrehttp://parallel.hpc.unsw.edu.au/rks
International prefix +612, Interstate prefix 02
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Description: PGP signature
RE: Quantum Rebel
Russell, I agree with what you state below. But consider the following
experiment.
Instead of two beams of equal intensity interfering, as in classical
inteferometry, one has unequal amplitude beams. Specifically,
Beam A: 0.9*exp(iax+ibz-iwt)
Beam B: 0.1*exp(-iax+ibz-iwt)
The interference pattern is of the form:
Interference field = [cos(ax)+i*0.8sin(ax)]exp(ibx-iwt)
So the resulting photon distribution follows the intensity, or the field
amplitude squared:
Interference intensity = 0.64+ 0.36*cos^2(ax)
This wave pattern will begin to appear after sufficient number of
photons, but each photon is always ~99% (81/82) likely to have
originated from Beam A, based on conservation.
If Beam A and Beam B had different amplitudes, you would maximize the
uncertainty of the photon origin since you have to say 50/50 likelihood
for a photon coming from either A or B.
The complementarity principle's strongest statement is 100% certainty,
and that cannot be attained. But we can still get an idea of the wave
interference pattern and 'which way' information with high (but not
100%) certainty in gray-transition cases such as above.
Fred
-Original Message-
From: Russell Standish [mailto:[EMAIL PROTECTED]
Sent: Saturday, August 14, 2004 2:51 AM
To: Fred Chen
Cc: 'Everything List'
Subject: Re: Quantum Rebel
On Fri, Aug 13, 2004 at 11:43:10PM -0700, Fred Chen wrote:
...
>
> A better (and far simpler) way to challenge complementarity would be
> to use a low-intensity interferogram in a photographic film or CCD. At
> first the photons being detected are few so the shot (particle-like)
> aspect is more obvious. As more photons are integrated, the classical
> interference pattern is observed. Can there be a transition region
> where both aspects are observable?
>
This does not challenge complementarity. Consider a double slit
apparatus with the photon source's intensity down so low that each
individual photon can be observed hitting the screen one at a time. But
when one plots the distribution of positions where the photons strike
the screen after observing many of them, the interference pattern
results. This is simple and uncomplicated, but is not what the
complementarity principle is about.
Now consider that you have information about which slit the photon
passed through before hitting the screen - ie each photon is labelled 1,
2, 1, 1, etc, according to whuch slit it passed through. Therefore, you
can separate the observed photons into two sets, according to which slit
the phtons passed through. The distribution of each subset corresponds
to a single slit experiment, and the final distribution must be the sum
of the two single slit experiements. But single slit experiments do not
have interference patterns - hence the sum cannot have an interference
pattern either.
Consequently, if you have any way of knowing which slit the photon went
through (the "which way" information), then you cannot have an
interference pattern. This is what the complementarity principle means.
Cheers
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a virus.
It is an electronic signature, that may be used to verify this email
came from me if you have PGP or GPG installed. Otherwise, you may safely
ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119
(mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119
(")
Australia[EMAIL PROTECTED]
Room 2075, Red Centre
http://parallel.hpc.unsw.edu.au/rks
International prefix +612, Interstate prefix 02
Re: Quantum Rebel - complementarity
Unfortunately, it seems that there are very few people seriously working on radical ideas like the models proposed by 't Hooft. My favorite idea is that particles are not real. You could imagine that QM is an effective statistical theory (similar to what 't Hooft says) in which particles appear in a similar way as virtual particles appear in quantum field theory. If the Feynman rules had been discovered by experimentalists, you would have discussions about photons and electrons violating causality except when we observe them... - Oorspronkelijk bericht - Van: "John M" <[EMAIL PROTECTED]> Aan: "Saibal Mitra" <[EMAIL PROTECTED]> CC: <[EMAIL PROTECTED]> Verzonden: Saturday, August 14, 2004 04:51 PM Onderwerp: Re: Quantum Rebel - complementarity > Thanks! Maybe even further? > John M > - Original Message - > From: "Saibal Mitra" <[EMAIL PROTECTED]> > To: "Russell Standish" <[EMAIL PROTECTED]>; "John M" > <[EMAIL PROTECTED]> > Cc: <[EMAIL PROTECTED]> > Sent: Saturday, August 14, 2004 10:35 AM > Subject: Re: Quantum Rebel - complementarity > > > > Maybe we should look at deterministic theories, such as: > > > > > > http://arxiv.org/abs/hep-th/0104219 > > > > John M wrote: > > > > > Yet it would be refreshing to approach the concept from another side > > > (another framework), - maybe a new one?? > > > > > >
Re: Quantum Rebel - complementarity
It is not clear that the theory proposed by 't Hooft is incompatible with EPR. As 't Hooft explains there are several loopholes in Bell's theorem. E.g. in a completely deterministic world you cannot claim that you could have chosen to measure a different component of the spin than the one you actually measured... - Oorspronkelijk bericht - Van: "Brent Meeker" <[EMAIL PROTECTED]> Aan: <[EMAIL PROTECTED]> Verzonden: Saturday, August 14, 2004 10:19 AM Onderwerp: RE: Quantum Rebel - complementarity > If it can't deal with EPR, what good is it? > > Brent Meeker > > >-Original Message- > >From: Saibal Mitra [mailto:[EMAIL PROTECTED] > >Sent: Saturday, August 14, 2004 2:35 PM > >To: Russell Standish; John M > >Cc: [EMAIL PROTECTED] > >Subject: Re: Quantum Rebel - complementarity > > > > > >Maybe we should look at deterministic theories, such as: > > > > > >http://arxiv.org/abs/hep-th/0104219 > > > >John M wrote: > > > >> Yet it would be refreshing to approach the concept > >from another side > >> (another framework), - maybe a new one?? > > > > > > >
RE: Quantum Rebel - complementarity
If it can't deal with EPR, what good is it? Brent Meeker >-Original Message- >From: Saibal Mitra [mailto:[EMAIL PROTECTED] >Sent: Saturday, August 14, 2004 2:35 PM >To: Russell Standish; John M >Cc: [EMAIL PROTECTED] >Subject: Re: Quantum Rebel - complementarity > > >Maybe we should look at deterministic theories, such as: > > >http://arxiv.org/abs/hep-th/0104219 > >John M wrote: > >> Yet it would be refreshing to approach the concept >from another side >> (another framework), - maybe a new one?? > > >
Re: Quantum Rebel - complementarity
Thanks! Maybe even further? John M - Original Message - From: "Saibal Mitra" <[EMAIL PROTECTED]> To: "Russell Standish" <[EMAIL PROTECTED]>; "John M" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Saturday, August 14, 2004 10:35 AM Subject: Re: Quantum Rebel - complementarity > Maybe we should look at deterministic theories, such as: > > > http://arxiv.org/abs/hep-th/0104219 > > John M wrote: > > > Yet it would be refreshing to approach the concept from another side > > (another framework), - maybe a new one?? > >
Re: Quantum Rebel
Russell Standish wrote:
Let |i> refer to the state where the photon travels on path i. Then
one can write down a few relations, such as:
|1> = 1/sqrt{2}|3> + 1/sqrt{2}|4> = |5>
|2> = 1/sqrt{2}|3> - 1/sqrt{2}|4> = |6>
If a photon is detected on path 5, then the probability it travelled
along path i is <5|i>. Since <5|1>=1 and <5|2>=0, we have "which way"
information.
Now inserting an absorber on path 4 is mathematically equivalent to
inserting a projection operator |3><3| in the middle of the
propagator. The the probability of a photon detected at path 5 taking
path i becomes <5|3><3|i>. Computing these values by the above
formulae gives:
<5|3><3|1>=1/2 and <5|3><3|2>=1/2
Thanks for the elaboration, it's been a while since I studied QM. A
question: I had thought the notion of "probability" only makes sense when
talking about actual measured outcomes, and that paths in a path integral
can only be assigned a probability amplitude, not a probability, since if
you tried to talk about the "probability" of each path (just by squaring the
path's amplitude, I guess) the probabilities would not necessarily add
together classically. Is my memory wrong, or when you talk about the
"probability" that a photon took a path i do you really mean the probability
amplitude?
Jesse Mazer
Re: Quantum Rebel - complementarity
Maybe we should look at deterministic theories, such as: http://arxiv.org/abs/hep-th/0104219 John M wrote: > Yet it would be refreshing to approach the concept from another side > (another framework), - maybe a new one??
Re: Quantum Rebel - complementarity
Dear Russell, I really would like to read (if ever) about that darn complementarity - based on/around a different example from the stale double-slit experiment (which it was really constructed for). IMO the 'double' nature of particle-wave is not (well?) understood and this resulted in sweating out the 'complementarity' syndrome to explain some hard-to-follow experimental results within the ongoing formalism. (I mean to match the quantized items within the system). Since 2x10^m million experiments - calculations and 3x10^n papers (not to speak about hundreds of prizes, tenthousands of tenure) have been devoted to the concept - taught to 3 consecutive generations of young receptive brains, it would be a BIG job to reformulate it. Yet it would be refreshing to approach the concept from another side (another framework), - maybe a new one?? John Mikes - Original Message - From: "Russell Standish" <[EMAIL PROTECTED]> To: "Fred Chen" <[EMAIL PROTECTED]> Cc: "'Everything List'" <[EMAIL PROTECTED]> Sent: Saturday, August 14, 2004 5:50 AM Subject: Re: Quantum Rebel
Re: Quantum Rebel
On Fri, Aug 13, 2004 at 11:43:10PM -0700, Fred Chen wrote:
...
>
> A better (and far simpler) way to challenge complementarity would be to
> use a low-intensity interferogram in a photographic film or CCD. At
> first the photons being detected are few so the shot (particle-like)
> aspect is more obvious. As more photons are integrated, the classical
> interference pattern is observed. Can there be a transition region where
> both aspects are observable?
>
This does not challenge complementarity. Consider a double slit
apparatus with the photon source's intensity down so low that each
individual photon can be observed hitting the screen one at a
time. But when one plots the distribution of positions where the
photons strike the screen after observing many of them, the
interference pattern results. This is simple and uncomplicated, but is
not what the complementarity principle is about.
Now consider that you have information about which slit the photon
passed through before hitting the screen - ie each photon is labelled
1, 2, 1, 1, etc, according to whuch slit it passed through. Therefore,
you can separate the observed photons into two sets, according to
which slit the phtons passed through. The distribution of each subset
corresponds to a single slit experiment, and the final distribution
must be the sum of the two single slit experiements. But single slit
experiments do not have interference patterns - hence the sum cannot
have an interference pattern either.
Consequently, if you have any way of knowing which slit the photon
went through (the "which way" information), then you cannot have an
interference pattern. This is what the complementarity principle means.
Cheers
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Australia[EMAIL PROTECTED]
Room 2075, Red Centrehttp://parallel.hpc.unsw.edu.au/rks
International prefix +612, Interstate prefix 02
pgpyItfmsIInq.pgp
Description: PGP signature
Re: Quantum Rebel
From: "Fred Chen" > Can there be a transition region where > both aspects are observable? It is difficult to observe a one-particle pattern http://www.optica.tn.tudelft.nl/education/photons.asp But if you are interested in things like whether there is an experimental smooth, Yin-Yang type :-), transition between the particle-like and the wave-like behaviour, try the links below. Greenberger and Yasin wrote P^2 + V^2 = 1, where P is the *probability* for the particle taking one of the two possible paths, and V the visibility of the fringes. http://arxiv.org/abs/quant-ph/9908072 http://arxiv.org/abs/quant-ph/0311179 http://arxiv.org/abs/quant-ph/0201026 http://arxiv.org/abs/quant-ph/0404013 In other words, the Greenberger and Yasin relation states that the "entity" has a double nature (wave-like,particle-like) and that there is a "smooth" transition between one and the other nature. Following Greenberger and Yasin, we must restate the complementarity principle as *coexistence* between particle-like and wave-like properties, and not as reciprocal *exclusion*. (Btw, it is well known that Heisenberg was against the complementarity principle, since in matrix mechanics there are no waves at all ... It is also well known that the Bohr-Heisenberg debate, on this point, was very hard indeed).
RE: Quantum Rebel
As long as the wires interact with the photons, the information is
destroyed. I made the nonzero width reality comment to further build up
the case. And you are right, a single wire should also do the trick.
A better (and far simpler) way to challenge complementarity would be to
use a low-intensity interferogram in a photographic film or CCD. At
first the photons being detected are few so the shot (particle-like)
aspect is more obvious. As more photons are integrated, the classical
interference pattern is observed. Can there be a transition region where
both aspects are observable?
-Original Message-
From: Russell Standish [mailto:[EMAIL PROTECTED]
Sent: Friday, August 13, 2004 11:29 PM
To: Fred Chen
Cc: 'Everything List'
Subject: Re: Quantum Rebel
It has nothing whatsoever to do with finite width of the absorber.
Adding an infinitesimally thin wire into the experiment is sufficient to
destroy "which way" information.
On Fri, Aug 13, 2004 at 11:24:06PM -0700, Fred Chen wrote:
> Yes I think this is correct.
>
> The theoretical zero amplitude region in the interference plane of the
> wires is also of zero width, while on the other hand the wires are
> obviously finite width. The wires do interact with the photons in
> reality, or equivalently, diffract the waves coming from the slits. So
> in the end each detector will detect photons coming from both slits.
> If you covered up one of the slits, but left the wires in place, both
> detectors will detect photons originating from the slit.
>
> So complementarity (if defined as exclusive particle/wave observation)
> has not been disproven. The particle-tracking information from each
> slit is destroyed by interaction with the wires.
>
> Fred
>
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a virus.
It is an electronic signature, that may be used to verify this email
came from me if you have PGP or GPG installed. Otherwise, you may safely
ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119
(mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119
(")
Australia[EMAIL PROTECTED]
Room 2075, Red Centre
http://parallel.hpc.unsw.edu.au/rks
International prefix +612, Interstate prefix 02
Re: Quantum Rebel
It has nothing whatsoever to do with finite width of the
absorber. Adding an infinitesimally thin wire into the experiment is
sufficient to destroy "which way" information.
On Fri, Aug 13, 2004 at 11:24:06PM -0700, Fred Chen wrote:
> Yes I think this is correct.
>
> The theoretical zero amplitude region in the interference plane of the
> wires is also of zero width, while on the other hand the wires are
> obviously finite width. The wires do interact with the photons in
> reality, or equivalently, diffract the waves coming from the slits. So
> in the end each detector will detect photons coming from both slits. If
> you covered up one of the slits, but left the wires in place, both
> detectors will detect photons originating from the slit.
>
> So complementarity (if defined as exclusive particle/wave observation)
> has not been disproven. The particle-tracking information from each slit
> is destroyed by interaction with the wires.
>
> Fred
>
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Australia[EMAIL PROTECTED]
Room 2075, Red Centrehttp://parallel.hpc.unsw.edu.au/rks
International prefix +612, Interstate prefix 02
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RE: Quantum Rebel
Yes I think this is correct. The theoretical zero amplitude region in the interference plane of the wires is also of zero width, while on the other hand the wires are obviously finite width. The wires do interact with the photons in reality, or equivalently, diffract the waves coming from the slits. So in the end each detector will detect photons coming from both slits. If you covered up one of the slits, but left the wires in place, both detectors will detect photons originating from the slit. So complementarity (if defined as exclusive particle/wave observation) has not been disproven. The particle-tracking information from each slit is destroyed by interaction with the wires. Fred -Original Message- From: scerir [mailto:[EMAIL PROTECTED] Sent: Wednesday, August 11, 2004 2:12 PM To: Everything List Subject: Re: Quantum Rebel It seems (to me, et al.) that the (supposed) information Afshar gets about the "which way" at the screen, is different from the usual information about the "which way" one gets at the slits, or from the (probabilistic) information about the "which way" one can have even before the slits (in case of asymmetry). This seems to be the point. So there is a problem here. Because we know that information about the "which way" at (or before) the slits does destroy the interference pattern completely (partially if the information has a probabilitic nature). On the contrary the "which way" information Afshar thinks he gets (via those lenses) at the screen, does not destroy the interference pattern (at the wires, which is a different place and time from the screen). So how Afshar gets this information? Via optics, geometrical optics, straight lines. That is to say that a photon goes following straight lines between the slit and the detector, but (apparently) goes "interferential" at the wires. (I wrote apparently because at the wires, imo, there is no measurement, but a "negative" or "non-demolitive" or "weak" measurement). All that seems not consistent. So the information Afshar gets at the screen, via those lenses, is not real, or proper. Because the conservation of momentum (the conservation of distribution of momentum) forbids all that, imo. [fwding what Basil Hiley thinks ...] Thanks for the copy of the New Scientist's article about Afshar's experiment. Unfortunately it is no challenge to Bohr's position. How on earth does he know the photons arriving at detector 1 come from pinhole 1 when both pinholes are open? You cannot use ray optics in the region where the light from the two pinholes overlap so you cannot draw any such conclusion. Lets look at the claim a little more closely. Afshar is quoted as saying "According to my experiment one of the key assumptions about quantum theory is wrong." Ok what assumption? The article doesn't say. It mutters something about Bohr and goes on to say "When faced with a classical apparatus these mysterious quantum entities will either show a particle-like or a wave-like face." Where has this sloppy thinking come from? Bohr never said any such thing. What Bohr actually said was 'However, since the discovery of the quantum of action, we know that the classical ideal cannot be attained in the description of atomic phenomena. In particular, any attempt at an ordering in space-time leads to a break in the causal chain, since such an attempt is bound up with an essential exchange of momentum and energy between the individuals and the measuring rods and clocks used for observation; and just this exchange cannot be taken into account if the measuring instruments are to fulfil their purpose. Conversely, any conclusion, based in an unambiguous manner upon the strict conservation of energy and momentum, with regard to the dynamical behaviour of the individual units obviously necessitates a complete renunciation of following their course in space and time'. [Bohr, Atomic Theory and the Description of Nature, pp. 97-8, Cambridge University Press, 1934] Notice the phrase 'following their course in space and time'. This is not a discussion about particles 'behaving only like waves or only like particles'. It is about 'following' or 'looking at' the process using some suitable instrument. So if you 'look at' each photon as it passes through one pinhole you won't get an interference pattern. Even the Bohm approach agrees with that. OK after that little rebuff we finally come to Afshar's real claim. It is that his experiment is "recording the rate at which photons are coming through each pinhole". If this statement was correct then it would imply that "there should be no interference pattern" where the beams overlap. "But there is, Afshar says". Sure there is an interference effect simply be
Re: Quantum Rebel
Russell Standish wrote: The presence or absence of the absorber on path 4 changes the wavefunctions involved, even though the amplitude of the wavefunction along path 4 is zero. How exactly does it change the wavefunctions involved? If the outcome of the experiment is exactly the same, the amplitude-squared of the wavefunction must be unchanged at all points, so is it just a phase shift? Have you actually done a calculation to see how the wavefunction is changed? The same is true with Afshar's experiment. This may seem nonsensical, but its exactly what QM says happens, and this sort of thing has been seen often in quantum experiments. The Aharanov-Bohm effect comes to mind. In the Aharonov-Bohm setup, would the charged particle's wavefunction actually have an amplitude of zero inside the solenoid containing the magnetic field, or is their some nonzero probability that you will observe it inside the solenoid? If the latter, this isn't really analogous to Afshar's experiment or Unruh's variation on it. Jesse Mazer
Re: Quantum Rebel
On Thu, Aug 12, 2004 at 11:28:33AM -0400, Jesse Mazer wrote:
> Russell Standish wrote:
>
> Hmm, on rereading the last section of Unruh's article I see you're
> correct--in the second-to-last paragraph he says "However, while in the
> interference experiment, the presence or absence of the absorber in path 4
> would seem to make no difference-- no photons travel along path 4 to be
> absorbed-- it makes a crucial difference in the interpretation. A critical
> part of the the interpretation is drawing the inference that IF the
> particle was detected in detector 5, THEN it must have come from path 1.
> Similarly, IF it was detected in detector 6, then it came from path 2. The
> presence of the absorber in path 4 does not change the experiment, but it
> destroys these inferential chains."
>
> I'm a little confused by his answer though, because he says the presence or
> absence of the absorber along path 4 in figure 2 makes absolutely no
> difference to the outcome of the experiment, since interference insures no
> photons would travel along path 4 even without the absorber there. So if
> you placed a continuous screen in the position of the two detectors, you'd
> still get two distinct spots with no interference fringes between
> them...and doesn't complementarity say that the absence of interference
> between two spots on a screen in the double-slit experiment can only occur
> when you *do* know which hole the photons landing on each spot went through?
"no difference to the outcome of the experiment", but a big difference
to the information obtained from the experiment. In the first case
(without the path 4 absorber), which detector a photon arrives at is
correlated with which path it took between path 1&2. With the path 4
absorber, one can no longer obtain that information. Weird perhaps,
but entirely in line with what QM predicts.
>
> Along the same lines, I'm confused about exactly how your answer fits with
> Unruh's answer. You said:
>
> >Now in the article, Afshar claims to have measured which slit the
> >photon passed through and verified the existence of an interference
> >pattern. However, this is not the case - without the wires in
> >place to detect the presence of the interference pattern, photons
> >arriving at detector A have passed through slit A, and vice-versa with
> >detector B and slit B. However, with the wires in place, some photons
> >are scattered, indeed some photons which passed through slit A will
> >arrive at detector B. With both slits open, and the wire placed
> >exactly at a null point of the interference pattern, the photons
> >passing through slit A and arriving at detector B exactly counteracts
> >the photons passing thoguh slit B that have been lost through
> >scattering. The mathematics of quantum mechanics assures this,
> >coincidental this may seem.
>
> Is Unruh saying that in figure 2 without the absorber, the amplitude of a
> photon travelling along path 4 is zero, but with the absorber in place,
> there is some nonzero amplitude for a photon to travel along path 4 but
> then be scattered into the "wrong" detector?
The presence or absence of the absorber on path 4 changes the
wavefunctions involved, even though the amplitude of the wavefunction
along path 4 is zero. The same is true with Afshar's experiment. This
may seem nonsensical, but its exactly what QM says happens, and this
sort of thing has been seen often in quantum experiments. The
Aharanov-Bohm effect comes to mind.
More likely the source of the paradox is the incorrect belief that
placing an absorber/detector at a zero amplitude site will not affect
the experiment.
If he's not suggesting the
> possibility the absorber will scatter photons without absorbing them is
> relevant here, then I wouldn't think he'd say the possibility the wires
> will scatter photons without absorbing them is relevant to Afshar's
> experiment. When you say "the mathematics of quantum mechanics assures
> this", did you actually do a calculation of the effects of scattering in
> Afshar's experiment?
>
> Jesse Mazer
>
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Re: Quantum Rebel
From: "John Collins"
> Essentially Ashfar's experiment involves fooling himself
> (and perhaps a few others) with a new single-path photon
> thoery, then undermning the new theory, whcih was not quantum
> mechanics..
The orthodox QM says that if we have the usual two-slit,
a "which way" detector, and the screen, the interference
pattern is destroyed as soon as the detector finds (with
probability 1) the "which way". In principle this is true
also in the case of single particles. In practice you need
many particles. (If the detector finds the "which way" with
probability < 1, the interference pattern is destroyed
partially, because there is a Greenberger & Yasin equation,
and so on ...).
The orthodox QM also says that is we put a "which way eraser"
between the (working) "which way" detector and the screen,
the interference pattern is restored. But where it is restored?
At the screen of course.
Now in the Afshar experiment those lenses are (supposed to be)
"which way detectors". Now if we insert, after each of those lenses,
the "which way eraser", an interference pattern - according to
orthodox QM - will be restored. But where it will be restored?
At the screen (here - in Afshar exp. - I do not know if there is
a screen, but in principle it could be so).
It seems to me that the "which way eraser" affects what happens
"after", but does not affect what already happened "before". But
if that is true for the "which way eraser", it must be true
also for the "which way detector". That is to say that any "which
way detector" does affect what happens "after" but does not
affect what already happened "before".
If the above is true - but I doubt it, since here is late, hot, and
dark ! - assuming (as Afshar/Cramer) that those lenses ("which way
detectors") should affect what already happened "before", at
those little wires level, is not solid at all.
s.
Btw, it is not so simple to define "complementarity".
Between "waves" (are there "waves" in Matrix Mechanics?) and
"particles"? Between localization and superposition of amplitudes
(von Weizsaecker)? Between interference pattern and "which way"
knowledge? Between continuous and discontinuous? Between
separability and unitarity? Between reversibility and
irreversibility? This one seems to be close to what Lawrence Bragg
said: "Everything in the future is a wave, everything in the past
is a particle"!
Re: Quantum Rebel
- Original Message - From: "Jesse Mazer" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, August 12, 2004 4:28 PM Subject: Re: Quantum Rebel > Is Unruh saying that in figure 2 without the absorber, the amplitude of a > photon travelling along path 4 is zero, but with the absorber in place, > there is some nonzero amplitude for a photon to travel along path 4 but then > be scattered into the "wrong" detector? If he's not suggesting the > possibility the absorber will scatter photons without absorbing them is > relevant here, then I wouldn't think he'd say the possibility the wires will > scatter photons without absorbing them is relevant to Afshar's experiment. > When you say "the mathematics of quantum mechanics assures this", did you > actually do a calculation of the effects of scattering in Afshar's > experiment? > > Jesse Mazer > Until the photon reaches the detector, the mathematics of quantum mechanics are the essentially the same as that of a classical wave, but are not the same as the 'ray tracing' approximation. Without the wires there, according to quantum meachanics, the photon will travel like a wave, passing through both initial slits, forming a diffraction pattern, and eventually producing a superposition of two different states corresponding to the two detectors having been hit. This superposition is unstable and decoheres (thats what makes them 'detectors'; if instead you had two new slits, you could leave the photon to perform more interference shenanigans). The presence of the wires shows that the 'state vector collapse' occurs after the photon reaches the detectors, not at the slits, which is obvious with a flat screen as the detector, but the two detectors positioned at the geometrically significant positions creates the illusion of each photon having traced a single ray-like path. Essentially Ashfar's experiment involves fooling himself (and perhaps a few others) with a new single-path photon thoery, then undermning the new theory, whcih was not quantum mechanics.. --Chris Collins
Re: Quantum Rebel
Russell Standish wrote: On Thu, Aug 12, 2004 at 01:08:36AM -0400, Jesse Mazer wrote: Also notice that in the analysis of Afshar's experiment by W. Unruh at http://axion.physics.ubc.ca/rebel.html which scerir linked to, Unruh does not dispute Afshar's claim that all the photons from the each pinhole end up in a single detector. In fact, he offers a "simpler version of the experiment" involving a multiple pass interferometer, depicted in figure 2, and says that in this experiment you do know which path a photon took by looking at which detector it hits: "By measuring which detector they triggered, 5 or 6, one measures which of the beams, 1 or 2, the photon traveled along". Since the experiment in figure 2 is just supposed to be a "simpler version" of Afshar's experiment, it's pretty clear that Unruh would not disagree that the lens insures that knowing which detector absorbed a photon is enough to tell you which path the photon must have taken through the pinholes. Unruh is a fairly big-name physicist and his explanation of what's wrong with Afshar's conclusions about complementarity are pretty detailed, while I don't know anything about Basil Hiley and his criticisms are more vague. After looking at Unruh's explanation, I can only say that he puts in a very persuasive manner, the substance of my post to this list: namely that the insertion of a diffraction grating (equiv. Unruh's path 4 absorber) destroys the "which-way" information. Hmm, on rereading the last section of Unruh's article I see you're correct--in the second-to-last paragraph he says "However, while in the interference experiment, the presence or absence of the absorber in path 4 would seem to make no difference-- no photons travel along path 4 to be absorbed-- it makes a crucial difference in the interpretation. A critical part of the the interpretation is drawing the inference that IF the particle was detected in detector 5, THEN it must have come from path 1. Similarly, IF it was detected in detector 6, then it came from path 2. The presence of the absorber in path 4 does not change the experiment, but it destroys these inferential chains." I'm a little confused by his answer though, because he says the presence or absence of the absorber along path 4 in figure 2 makes absolutely no difference to the outcome of the experiment, since interference insures no photons would travel along path 4 even without the absorber there. So if you placed a continuous screen in the position of the two detectors, you'd still get two distinct spots with no interference fringes between them...and doesn't complementarity say that the absence of interference between two spots on a screen in the double-slit experiment can only occur when you *do* know which hole the photons landing on each spot went through? Along the same lines, I'm confused about exactly how your answer fits with Unruh's answer. You said: Now in the article, Afshar claims to have measured which slit the photon passed through and verified the existence of an interference pattern. However, this is not the case - without the wires in place to detect the presence of the interference pattern, photons arriving at detector A have passed through slit A, and vice-versa with detector B and slit B. However, with the wires in place, some photons are scattered, indeed some photons which passed through slit A will arrive at detector B. With both slits open, and the wire placed exactly at a null point of the interference pattern, the photons passing through slit A and arriving at detector B exactly counteracts the photons passing thoguh slit B that have been lost through scattering. The mathematics of quantum mechanics assures this, coincidental this may seem. Is Unruh saying that in figure 2 without the absorber, the amplitude of a photon travelling along path 4 is zero, but with the absorber in place, there is some nonzero amplitude for a photon to travel along path 4 but then be scattered into the "wrong" detector? If he's not suggesting the possibility the absorber will scatter photons without absorbing them is relevant here, then I wouldn't think he'd say the possibility the wires will scatter photons without absorbing them is relevant to Afshar's experiment. When you say "the mathematics of quantum mechanics assures this", did you actually do a calculation of the effects of scattering in Afshar's experiment? Jesse Mazer
Re: Quantum Rebel
It seems that Cramer has something to say about those wires (as diffraction grating). s. - A number of your readers [New Scientist] have pointed out that Afshar's grid wires are placed in just the positions that would form a diffraction grating creating an image of pinhole 1 at the position of the pinhole 2 image. Does this destroy the purity of Afshar's "which-way" measurement? I raised the same question with Afshar earlier this year, and the answer is no. Reason: the wires intercept no light and so cannot diffract. He has done a variation of his experiment using ONLY A SINGLE WIRE and recorded all the light in the focal plane of the pinholes under three conditions: (1) wire in, one pinhole; (2) wire in, two pinholes; and (3) wire out, two pinholes. Measurement (1) shows lots of scattering from the wire away from the image points, indicating that with only one pinhole open the wire is intercepting and scattering light. Measurements (2) and (3) show clear images of the pinholes with nothing in between and are indistinguishable. Conclusion: no light is scattered or intercepted by the wire in measurement (2) because the interference pattern is present, and the wire is at an intensity-zero position of the pattern. A single wire cannot function as a diffraction grating. Bohr is still wrong. John G. Cramer Professor of Physics University of Washington
Re: Quantum Rebel
On Thu, Aug 12, 2004 at 01:08:36AM -0400, Jesse Mazer wrote:
>
> Also notice that in the analysis of Afshar's experiment by W. Unruh at
> http://axion.physics.ubc.ca/rebel.html which scerir linked to, Unruh does
> not dispute Afshar's claim that all the photons from the each pinhole end
> up in a single detector. In fact, he offers a "simpler version of the
> experiment" involving a multiple pass interferometer, depicted in figure 2,
> and says that in this experiment you do know which path a photon took by
> looking at which detector it hits: "By measuring which detector they
> triggered, 5 or 6, one measures which of the beams, 1 or 2, the photon
> traveled along". Since the experiment in figure 2 is just supposed to be a
> "simpler version" of Afshar's experiment, it's pretty clear that Unruh
> would not disagree that the lens insures that knowing which detector
> absorbed a photon is enough to tell you which path the photon must have
> taken through the pinholes. Unruh is a fairly big-name physicist and his
> explanation of what's wrong with Afshar's conclusions about complementarity
> are pretty detailed, while I don't know anything about Basil Hiley and his
> criticisms are more vague.
After looking at Unruh's explanation, I can only say that he puts in a
very persuasive manner, the substance of my post to this list: namely
that the insertion of a diffraction grating (equiv. Unruh's path 4
absorber) destroys the "which-way" information.
So Unruh does not claim that the lens suffices to tell you which path
the photon takes in the presence of the diffraction grating.
--
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A/Prof Russell Standish Director
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UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Australia[EMAIL PROTECTED]
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Re: Quantum Rebel
scerir quotes Basil Hiley saying: Sure there is an interference effect simply because Afshar's experiments do not 'follow' anything and they do not 'look at' each photon as it passes through a pinhole. He is simply collecting and counting the distribution of photon arrivals at his two detectors. Then he makes inferences about what could possibly be going on and concludes, incorrectly that a photon detected in the 'photon detector for pinhole 1' came from pinhole 1. However that conclusion is based on the assumption that the rays emanating from pinhole 1 arrive at the 'photon detector for pinhole 1'. But the ray picture breaks down as soon as you enter the region of overlap of the two beams and you cannot conclude that the photon entering pinhole 1 arrives at the 'photon detector for pinhole 1'. You haven't measured which pinhole each photon passed through so you have not contradicted Bohr. Unfortunately Afshar's conclusion, "According to my experiment one of the key assumptions about quantum theory is wrong" is incorrect. His conclusion is wrong simply because he doesn't understand the physical optics that lies behind the experiment he is doing. I think Basil Hiley's analysis here may be incorrect. In the normal double-slit experiment, the interference pattern in probabilities you get from quantum physics when you don't know which slit the photon went through is the same as the interference pattern in light intensities you get from classical optics when you shine a light through two slits. So, if classical optics predicts that light from two pinholes shining on a lens will be focused onto two distinct spots, with no interference between the spots and with all the light from one pinhole focused on one spot, then it seems likely that quantum mechanics would predict the same thing. Also notice that in the analysis of Afshar's experiment by W. Unruh at http://axion.physics.ubc.ca/rebel.html which scerir linked to, Unruh does not dispute Afshar's claim that all the photons from the each pinhole end up in a single detector. In fact, he offers a "simpler version of the experiment" involving a multiple pass interferometer, depicted in figure 2, and says that in this experiment you do know which path a photon took by looking at which detector it hits: "By measuring which detector they triggered, 5 or 6, one measures which of the beams, 1 or 2, the photon traveled along". Since the experiment in figure 2 is just supposed to be a "simpler version" of Afshar's experiment, it's pretty clear that Unruh would not disagree that the lens insures that knowing which detector absorbed a photon is enough to tell you which path the photon must have taken through the pinholes. Unruh is a fairly big-name physicist and his explanation of what's wrong with Afshar's conclusions about complementarity are pretty detailed, while I don't know anything about Basil Hiley and his criticisms are more vague. Anyway, after thinking more about this experiment it's clear to me that even if the lens is enough to insure that all photons from the left pinhole end up in the right detector and vice versa, complementarity should still predict that wires placed at the interference minima will not register any hits. Consider modifying Afshar's experiment by adding extra wires at positions other than the interference minima, and sending the photons through the pinholes one-by-one. In some cases the photon will be registered at one of the wires in front of the lens, in others it will be registered at one of the detectors behind the lens. Now, if you consider *only* the subset of cases where the photon was absorbed by a wire, in these cases the photon never passed through the lens, so you have absolutely no information on which pinhole these photons went through. So if you compare the frequency that the photons hit different wires, complementarity must predict that you'll get an interference pattern--wires closer to the interference maxima will register more hits, wires closer to the interference minima will register fewer hits, and wires placed exactly at the minima will register zero. So why should an advocate of complementarity be surprised that, after removing all the wires *except* those placed exactly at the minima, these wires continue to register zero hits? You could also turn this into a "proof-by-contradiction" that complementarity actually demands that wires exactly at the minima will not register any photons. Suppose in Afshar's experiment you sent photons through one-by-one, and found that there was some nonzero number of cases where the photons hit one of the wires at the minima. Since these photons did not make it to the lens, you have no information about which slit they went through, and so complemantarity says that the probability of finding these photons in any given location is determined by an interference pattern. But the interference pattern predicts *zero* probability of findi
Re: Quantum Rebel
It seems (to me, et al.) that the (supposed) information Afshar gets about the "which way" at the screen, is different from the usual information about the "which way" one gets at the slits, or from the (probabilistic) information about the "which way" one can have even before the slits (in case of asymmetry). This seems to be the point. So there is a problem here. Because we know that information about the "which way" at (or before) the slits does destroy the interference pattern completely (partially if the information has a probabilitic nature). On the contrary the "which way" information Afshar thinks he gets (via those lenses) at the screen, does not destroy the interference pattern (at the wires, which is a different place and time from the screen). So how Afshar gets this information? Via optics, geometrical optics, straight lines. That is to say that a photon goes following straight lines between the slit and the detector, but (apparently) goes "interferential" at the wires. (I wrote apparently because at the wires, imo, there is no measurement, but a "negative" or "non-demolitive" or "weak" measurement). All that seems not consistent. So the information Afshar gets at the screen, via those lenses, is not real, or proper. Because the conservation of momentum (the conservation of distribution of momentum) forbids all that, imo. [fwding what Basil Hiley thinks ...] Thanks for the copy of the New Scientist's article about Afshar's experiment. Unfortunately it is no challenge to Bohr's position. How on earth does he know the photons arriving at detector 1 come from pinhole 1 when both pinholes are open? You cannot use ray optics in the region where the light from the two pinholes overlap so you cannot draw any such conclusion. Lets look at the claim a little more closely. Afshar is quoted as saying "According to my experiment one of the key assumptions about quantum theory is wrong." Ok what assumption? The article doesn't say. It mutters something about Bohr and goes on to say "When faced with a classical apparatus these mysterious quantum entities will either show a particle-like or a wave-like face." Where has this sloppy thinking come from? Bohr never said any such thing. What Bohr actually said was 'However, since the discovery of the quantum of action, we know that the classical ideal cannot be attained in the description of atomic phenomena. In particular, any attempt at an ordering in space-time leads to a break in the causal chain, since such an attempt is bound up with an essential exchange of momentum and energy between the individuals and the measuring rods and clocks used for observation; and just this exchange cannot be taken into account if the measuring instruments are to fulfil their purpose. Conversely, any conclusion, based in an unambiguous manner upon the strict conservation of energy and momentum, with regard to the dynamical behaviour of the individual units obviously necessitates a complete renunciation of following their course in space and time'. [Bohr, Atomic Theory and the Description of Nature, pp. 97-8, Cambridge University Press, 1934] Notice the phrase 'following their course in space and time'. This is not a discussion about particles 'behaving only like waves or only like particles'. It is about 'following' or 'looking at' the process using some suitable instrument. So if you 'look at' each photon as it passes through one pinhole you won't get an interference pattern. Even the Bohm approach agrees with that. OK after that little rebuff we finally come to Afshar's real claim. It is that his experiment is "recording the rate at which photons are coming through each pinhole". If this statement was correct then it would imply that "there should be no interference pattern" where the beams overlap. "But there is, Afshar says". Sure there is an interference effect simply because Afshar's experiments do not 'follow' anything and they do not 'look at' each photon as it passes through a pinhole. He is simply collecting and counting the distribution of photon arrivals at his two detectors. Then he makes inferences about what could possibly be going on and concludes, incorrectly that a photon detected in the 'photon detector for pinhole 1' came from pinhole 1. However that conclusion is based on the assumption that the rays emanating from pinhole 1 arrive at the 'photon detector for pinhole 1'. But the ray picture breaks down as soon as you enter the region of overlap of the two beams and you cannot conclude that the photon entering pinhole 1 arrives at the 'photon detector for pinhole 1'. You haven't measured which pinhole each photon passed through so you have not contradicted Bohr. Unfortunately Afshar's conclusion, "According to my experiment one of the key assumptions about quantum theory is wrong" is incorrect. His conclusion is wrong simply because he doesn't understand the physical optics that lies behind the experiment he is doing
Re: Quantum Rebel
Hi Russel I just came back from vacation and am catching up with the list. Are you claiming that photon particles are redirected to the detectors by diffraction around the wires? If so your objection to Afshar's experiment is not valid because you presupposes that the photons are waves obeying diffraction rules. Quantum mechanics does predicts Afshar's experiment when it is applied inconsistenly. Afshar's experiment highlights these inconsistencies. George Russell Standish wrote: I just read the New Scientist article "Quantum Rebel" last night about Shariar Afshar's work on the double slit experiment. Ingenious as the experiment is, I really don't think it says anything about different interpretations of QM. Indeed, the outcome of the experiment is just what I'd expect from quantum theory, regardless of which interpretation is used. OK - so the claim is that Bohr's complementarity principle (CP) is tested by this experiment and found wanting. I decided to go back to the two text books I learnt quantum mechanics from - Leonard Schiff's book which is the older and more traditional of the two, and Rammamurti Shankar's book which has the more modern approach, but which I found explained things better. Shankar doesn't mention the CP at all, and for Schiff, the CP is basically a restatement of the Heisenberg uncertainty principle, a principle not tested by Afshar's experiment. In the double slit experiment, how I understand the CP to work is that one cannot measure which slit a photon passes through, and retain an interference pattern. Assuming it is possible to do this, one could divide the measures data into those photons that passed through slit A, and those that passed through slit B. The resulting distribution of photons arriving at the screen of the two slit experiment is then the sum of the distributions of the two subsets of data. However, the two sub distributions do not have inteference patterns so how can the sum have an interference pattern. Hence any such measurement of which slit the photon passes through must affect the photons so as to destroy the intereference pattern. Now in the article, Afshar claims to have measured which slit the photon passed through and verified the existence of an interference pattern. However, this is not the case - without the wires in place to detect the presence of the interference pattern, photons arriving at detector A have passed through slit A, and vice-versa with detector B and slit B. However, with the wires in place, some photons are scattered, indeed some photons which passed through slit A will arrive at detector B. With both slits open, and the wire placed exactly at a null point of the interference pattern, the photons passing through slit A and arriving at detector B exactly counteracts the photons passing thoguh slit B that have been lost through scattering. The mathematics of quantum mechanics assures this, coincidental this may seem. It may be a question of "interpretations of interpretations of QM", however on the basis of the New Scientist article, I don't believe Afshar have shown a problem with the complementarity principle. Cheers
Re: Quantum Rebel
http://www.analogsf.com/0409/altview2.shtml just Cramer talking about Afshar and MWI and his transactional interpretation (but why transactions occur exactly in the right place and moment is difficult to realize) s.
Re: Quantum Rebel
From: "John M" > I think your e-mails arrived blank > because you did not write into it. No no. It is a fuzzy effect. Due to the signature/attachment, my Outlook, my Norton Antivirus, and something else. But I can read now the body of the (blank) message in the window "properties of the message" --> "details" --> "original message". It is not so easy ... but it works. :-) s.
Re: Quantum Rebel
Russell, your body got through.
I think your e-mails arrived blank because you did not write into it.
True: some spam-hunter softwares may consider the lengthy rapsheet of all
your titles and addresses (+numbers) as sort of a spam, but most such
softwares give a warning, or delete the entire mail altogether. To "get" the
blanked off e-mail and the attachments may be funny. (It seems I hit
several nerves with my virus-paranoia).
John M
- Original Message -
From: "Russell Standish" <[EMAIL PROTECTED]>
To: "scerir" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Wednesday, July 28, 2004 9:20 PM
Subject: Re: Quantum Rebel
> Can anyone tell me why the body of the email is blank to some people?
> Is it some overzealous defang program the removes the body as well as
> the attachment?
>
> I don't care if the attachment is removed - it doesn't contain
> information - its purpose is to authenticate the letter only, and can
> be safely ignored by anyone who doesn't care.
>
> I'll send this email unsigned, to make sure the body gets through...
>
> Cheers
>
> On Wed, Jul 28, 2004 at 06:08:40PM +0200, scerir wrote:
> >
> > > *PS: A number of people ask me about the attachment to my email, which
> > > is of type "application/pgp-signature".
> >
> > The problem with that signature is that we (or just me?) do not receive
> > any text, in the body of the msg. Just blank.
>
> --
> *PS: A number of people ask me about the attachment to my email, which
> is of type "application/pgp-signature". Don't worry, it is not a
> virus. It is an electronic signature, that may be used to verify this
> email came from me if you have PGP or GPG installed. Otherwise, you
> may safely ignore this attachment.
>
> --
--
> A/Prof Russell StandishDirector
> High Performance Computing Support Unit, Phone 9385 6967, 8308 3119
(mobile)
> UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
> Australia[EMAIL PROTECTED]
> Room 2075, Red Centre
http://parallel.hpc.unsw.edu.au/rks
> International prefix +612, Interstate prefix 02
> --
--
>
Re: Quantum Rebel
Can anyone tell me why the body of the email is blank to some people?
Is it some overzealous defang program the removes the body as well as
the attachment?
I don't care if the attachment is removed - it doesn't contain
information - its purpose is to authenticate the letter only, and can
be safely ignored by anyone who doesn't care.
I'll send this email unsigned, to make sure the body gets through...
Cheers
On Wed, Jul 28, 2004 at 06:08:40PM +0200, scerir wrote:
>
> > *PS: A number of people ask me about the attachment to my email, which
> > is of type "application/pgp-signature".
>
> The problem with that signature is that we (or just me?) do not receive
> any text, in the body of the msg. Just blank.
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Australia[EMAIL PROTECTED]
Room 2075, Red Centrehttp://parallel.hpc.unsw.edu.au/rks
International prefix +612, Interstate prefix 02
Re: Quantum Rebel
Not me but Russell wrote that. I should have made that clear better when I posted Russell's attachment (Sorry Russell!). - Oorspronkelijk bericht - Van: "Jesse Mazer" <[EMAIL PROTECTED]> Aan: <[EMAIL PROTECTED]> Verzonden: Wednesday, July 28, 2004 08:59 PM Onderwerp: Re: Quantum Rebel > Saibal Mitra wrote: > > >Now in the article, Afshar claims to have measured which slit the > >photon passed through and verified the existence of an interference > >pattern. However, this is not the case - without the wires in > >place to detect the presence of the interference pattern, photons > >arriving at detector A have passed through slit A, and vice-versa with > >detector B and slit B. However, with the wires in place, some photons > >are scattered, indeed some photons which passed through slit A will > >arrive at detector B. With both slits open, and the wire placed > >exactly at a null point of the interference pattern, the photons > >passing through slit A and arriving at detector B exactly counteracts > >the photons passing thoguh slit B that have been lost through > >scattering. The mathematics of quantum mechanics assures this, > >coincidental this may seem. > > A poster on sci.physics.research elaborates on this point a little with a > nice thought-experiment involving enlarging the wires until they are almost > touching, at which point you just have a new set of "slits": > > http://makeashorterlink.com/?W3F012BE8 > > >Now I haven't done any calculations or read the New Scientist article > >except looking at the lab setup graphics, but if I would hazard a quick > >guess, it would be that it will turn out that even if the wires are > >placed in the interference fields valleys, the finite width of the > >wires will diffract just enough photons to erase the which-way > >information that was gained by focusing the detectors at the holes in > >the wall through the lens. > > > >Consider the limiting case with wires placed with their centres in the > >interference fields valleys as before, but expand their width so much > >that they almost touch each other. What you have now is yet another > >wall with a bunch of slits in! Obviously, almost all which-way > >information is lost after the wavefronts pass these almost > >infinitesimal slits since they will diffract the photons equally no > >matter from which hole in the *first* wall they originated, so any > >detector placed after this obstacle will be like running a new > >multiple-slit interference setup (although with the lens now severely > >defocusing the too-closely placed new slits). And since the which-way > >information from the first wall is erased, interference is free to > >happen between the first and the second wall. After the secondary wall > >the detectors can pick up which-way information causing them to behave > >as if there was little subsequent interference. > > > >Conversely, the other limiting case is with no wires (or secondary > >wall) present. Then all which-way information is present and again the > >detectors behave as if there was no interference. > > > >The experiment shows a case in between these limits and the effect I > >guessed at above could (and should, according to traditional QM) turn > >out to always cancel any attempt to find both 100% interference and > >100% which-way information. This would be better showed with some > >calculations of course... > >
Re: Quantum Rebel
Actually, looking at the diagram and explanation of the experiment posted at http://www.kathryncramer.com/wblog/archives/000674.html I think Saibal Mitra and the sci.physics.research poster I quoted may have misunderstood what happened in this experiment. I may have misunderstood, but it sounded as if both were arguing that the finite width of the wires could erase some of the which-path information and explain why you'd see interference at the final detectors. But the diagram seems to say that *no* interference was found at the detectorsthe interference Afshar is talking about was just in the fact that no photons were scattering against the wires because they were all placed in the interference valleys. So the idea seems to be that interference is the explanation for why no photons scatter against the wires, but the focusing lens behind the wires makes sure that photons from the left slit always go to the left detector and the photons from the right slit always go to the right detector--this is the "violation of complementarity", that the photons behave like a wave in avoiding the wires but behave like particles when arriving at the detectors. I'm not sure that the notion of "complementarity" has ever been sufficiently well-defined to say that this experiment violates it though, and in any case, as long as the results of the experiment match the predictions made by the standard theory of quantum mechanics, it cannot be taken as a disproof of the Everett interpretation, since the basic idea of the Everett interpretation is to keep the standard rules for wavefunction evolution but just to drop the "collapse" idea (the projection postulate). Jesse
Re: Quantum Rebel
Saibal Mitra wrote: Now in the article, Afshar claims to have measured which slit the photon passed through and verified the existence of an interference pattern. However, this is not the case - without the wires in place to detect the presence of the interference pattern, photons arriving at detector A have passed through slit A, and vice-versa with detector B and slit B. However, with the wires in place, some photons are scattered, indeed some photons which passed through slit A will arrive at detector B. With both slits open, and the wire placed exactly at a null point of the interference pattern, the photons passing through slit A and arriving at detector B exactly counteracts the photons passing thoguh slit B that have been lost through scattering. The mathematics of quantum mechanics assures this, coincidental this may seem. A poster on sci.physics.research elaborates on this point a little with a nice thought-experiment involving enlarging the wires until they are almost touching, at which point you just have a new set of "slits": http://makeashorterlink.com/?W3F012BE8 Now I haven't done any calculations or read the New Scientist article except looking at the lab setup graphics, but if I would hazard a quick guess, it would be that it will turn out that even if the wires are placed in the interference fields valleys, the finite width of the wires will diffract just enough photons to erase the which-way information that was gained by focusing the detectors at the holes in the wall through the lens. Consider the limiting case with wires placed with their centres in the interference fields valleys as before, but expand their width so much that they almost touch each other. What you have now is yet another wall with a bunch of slits in! Obviously, almost all which-way information is lost after the wavefronts pass these almost infinitesimal slits since they will diffract the photons equally no matter from which hole in the *first* wall they originated, so any detector placed after this obstacle will be like running a new multiple-slit interference setup (although with the lens now severely defocusing the too-closely placed new slits). And since the which-way information from the first wall is erased, interference is free to happen between the first and the second wall. After the secondary wall the detectors can pick up which-way information causing them to behave as if there was little subsequent interference. Conversely, the other limiting case is with no wires (or secondary wall) present. Then all which-way information is present and again the detectors behave as if there was no interference. The experiment shows a case in between these limits and the effect I guessed at above could (and should, according to traditional QM) turn out to always cancel any attempt to find both 100% interference and 100% which-way information. This would be better showed with some calculations of course...
Re: Quantum Rebel
Saibal Mitra fwded > It may be a question of "interpretations of interpretations of QM", > however on the basis of the New Scientist article, I don't believe > Afshar have shown a problem with the complementarity principle. I agree. But imagine the usual two-slit set-up. And this unusual screen, to reveal the interference pattern ... _ _ _ _ _ _ They are a set of photographic plates, they can register both the photons and their directions, i.e. if they come from the upper or from the lower slit (photons coming from the upper slit hit the upper face of the photographic plate, photons coming from the lower slit hit the lower face, there is a principle of conservation of momentum after all). Calculations made by Zurek and Wooters show that this kind of screen works, that is it can reveal - in principle - both the "welcher weg" and the interference pattern. But the complementarity principle forbids that. > *PS: A number of people ask me about the attachment to my email, which > is of type "application/pgp-signature". The problem with that signature is that we (or just me?) do not receive any text, in the body of the msg. Just blank.
Re: Quantum Rebel
The probability that Russell's message contained a virus was low (he uses linux) but nonzero. So, I guess that's bad news for some of my copies in the multiverse. - Oorspronkelijk bericht - Van: "Jeanne Houston" <[EMAIL PROTECTED]> Aan: "CMR" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Verzonden: Wednesday, July 28, 2004 04:20 PM Onderwerp: Re: Quantum Rebel > I also deleted everything immediately, fearing the viral possibilities of > the attachments. > > Jeanne > > - Original Message - > From: "CMR" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Wednesday, July 28, 2004 9:40 AM > Subject: Re: Quantum Rebel > > > > Oops, I too was a victim of viral paranoia this AM and committed wholesale > > deletion of all attachment laden emails in my box including, apparently, > > Russel's. letter. Can someone send or forward me a copy? (of the letter > not > > a virus) ;) > > > > Thanks! > > > > > > > Please, Russell, > > > for the peace of our minds who believe in 'smart' viruses and have none > of > > > the software you indicated: > > > Could you at least put a word in the e-mail that thei comes from you? > (eg > > > "Safe from RS" or "from Russ" etc.) > > > I wanted to open this attachment in blind face and paranoid shiver, > > however > > > went first to FILE - Properties - 2nd page and checked the "from" line > at > > > the bottom. Boring. Even there it may be a virus usiing your mailbox - > > > before you detect it. > > > I am not the only one suffering from virus-paranioa. > > > Cheerz > > > John Mikes > > >
Re: Quantum Rebel
I also deleted everything immediately, fearing the viral possibilities of the attachments. Jeanne - Original Message - From: "CMR" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, July 28, 2004 9:40 AM Subject: Re: Quantum Rebel > Oops, I too was a victim of viral paranoia this AM and committed wholesale > deletion of all attachment laden emails in my box including, apparently, > Russel's. letter. Can someone send or forward me a copy? (of the letter not > a virus) ;) > > Thanks! > > > > Please, Russell, > > for the peace of our minds who believe in 'smart' viruses and have none of > > the software you indicated: > > Could you at least put a word in the e-mail that thei comes from you? (eg > > "Safe from RS" or "from Russ" etc.) > > I wanted to open this attachment in blind face and paranoid shiver, > however > > went first to FILE - Properties - 2nd page and checked the "from" line at > > the bottom. Boring. Even there it may be a virus usiing your mailbox - > > before you detect it. > > I am not the only one suffering from virus-paranioa. > > Cheerz > > John Mikes >
Re: Quantum Rebel
I just read the New Scientist article "Quantum Rebel" last night about
Shariar Afshar's work on the double slit experiment. Ingenious as the
experiment is, I really don't think it says anything about different
interpretations of QM. Indeed, the outcome of the experiment is just
what I'd expect from quantum theory, regardless of which
interpretation is used.
OK - so the claim is that Bohr's complementarity principle (CP) is tested
by this experiment and found wanting. I decided to go back to the two
text books I learnt quantum mechanics from - Leonard Schiff's book
which is the older and more traditional of the two, and Rammamurti
Shankar's book which has the more modern approach, but which I found
explained things better. Shankar doesn't mention the CP at all, and
for Schiff, the CP is basically a restatement of the Heisenberg
uncertainty principle, a principle not tested by Afshar's experiment.
In the double slit experiment, how I understand the CP to work is that
one cannot measure which slit a photon passes through, and retain an
interference pattern. Assuming it is possible to do this, one could
divide the measures data into those photons that passed through slit A,
and those that passed through slit B. The resulting distribution of
photons arriving at the screen of
the two slit experiment is then the sum of the distributions of the
two subsets of data. However, the two sub distributions do not have
inteference patterns so how can the sum have an interference
pattern. Hence any such measurement of which slit the photon passes
through must affect the photons so as to destroy the intereference
pattern.
Now in the article, Afshar claims to have measured which slit the
photon passed through and verified the existence of an interference
pattern. However, this is not the case - without the wires in
place to detect the presence of the interference pattern, photons
arriving at detector A have passed through slit A, and vice-versa with
detector B and slit B. However, with the wires in place, some photons
are scattered, indeed some photons which passed through slit A will
arrive at detector B. With both slits open, and the wire placed
exactly at a null point of the interference pattern, the photons
passing through slit A and arriving at detector B exactly counteracts
the photons passing thoguh slit B that have been lost through
scattering. The mathematics of quantum mechanics assures this,
coincidental this may seem.
It may be a question of "interpretations of interpretations of QM",
however on the basis of the New Scientist article, I don't believe
Afshar have shown a problem with the complementarity principle.
Cheers
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Australia[EMAIL PROTECTED]
Room 2075, Red Centrehttp://parallel.hpc.unsw.edu.au/rks
International prefix +612, Interstate prefix 02
- Oorspronkelijk bericht -
Van: "CMR" <[EMAIL PROTECTED]>
Aan: <[EMAIL PROTECTED]>
Verzonden: Wednesday, July 28, 2004 03:40 PM
Onderwerp: Re: Quantum Rebel
> Oops, I too was a victim of viral paranoia this AM and committed wholesale
> deletion of all attachment laden emails in my box including, apparently,
> Russel's. letter. Can someone send or forward me a copy? (of the letter
not
> a virus) ;)
>
> Thanks!
>
>
> > Please, Russell,
> > for the peace of our minds who believe in 'smart' viruses and have none
of
> > the software you indicated:
> > Could you at least put a word in the e-mail that thei comes from you?
(eg
> > "Safe from RS" or "from Russ" etc.)
> > I wanted to open this attachment in blind face and paranoid shiver,
> however
> > went first to FILE - Properties - 2nd page and checked the "from" line
at
> > the bottom. Boring. Even there it may be a virus usiing your mailbox -
> > before you detect it.
> > I am not the only one suffering from virus-paranioa.
> > Cheerz
> > John Mikes
>
Re: Quantum Rebel
Oops, I too was a victim of viral paranoia this AM and committed wholesale deletion of all attachment laden emails in my box including, apparently, Russel's. letter. Can someone send or forward me a copy? (of the letter not a virus) ;) Thanks! > Please, Russell, > for the peace of our minds who believe in 'smart' viruses and have none of > the software you indicated: > Could you at least put a word in the e-mail that thei comes from you? (eg > "Safe from RS" or "from Russ" etc.) > I wanted to open this attachment in blind face and paranoid shiver, however > went first to FILE - Properties - 2nd page and checked the "from" line at > the bottom. Boring. Even there it may be a virus usiing your mailbox - > before you detect it. > I am not the only one suffering from virus-paranioa. > Cheerz > John Mikes
Re: Quantum Rebel
Please, Russell, for the peace of our minds who believe in 'smart' viruses and have none of the software you indicated: Could you at least put a word in the e-mail that thei comes from you? (eg "Safe from RS" or "from Russ" etc.) I wanted to open this attachment in blind face and paranoid shiver, however went first to FILE - Properties - 2nd page and checked the "from" line at the bottom. Boring. Even there it may be a virus usiing your mailbox - before you detect it. I am not the only one suffering from virus-paranioa. Cheerz John Mikes - Original Message - From: "Russell Standish" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Tuesday, July 27, 2004 10:16 PM Subject: Quantum Rebel Attachments - no text at all.
Quantum Rebel
I just read the New Scientist article "Quantum Rebel" last night about
Shariar Afshar's work on the double slit experiment. Ingenious as the
experiment is, I really don't think it says anything about different
interpretations of QM. Indeed, the outcome of the experiment is just
what I'd expect from quantum theory, regardless of which
interpretation is used.
OK - so the claim is that Bohr's complementarity principle (CP) is tested
by this experiment and found wanting. I decided to go back to the two
text books I learnt quantum mechanics from - Leonard Schiff's book
which is the older and more traditional of the two, and Rammamurti
Shankar's book which has the more modern approach, but which I found
explained things better. Shankar doesn't mention the CP at all, and
for Schiff, the CP is basically a restatement of the Heisenberg
uncertainty principle, a principle not tested by Afshar's experiment.
In the double slit experiment, how I understand the CP to work is that
one cannot measure which slit a photon passes through, and retain an
interference pattern. Assuming it is possible to do this, one could
divide the measures data into those photons that passed through slit A,
and those that passed through slit B. The resulting distribution of
photons arriving at the screen of
the two slit experiment is then the sum of the distributions of the
two subsets of data. However, the two sub distributions do not have
inteference patterns so how can the sum have an interference
pattern. Hence any such measurement of which slit the photon passes
through must affect the photons so as to destroy the intereference
pattern.
Now in the article, Afshar claims to have measured which slit the
photon passed through and verified the existence of an interference
pattern. However, this is not the case - without the wires in
place to detect the presence of the interference pattern, photons
arriving at detector A have passed through slit A, and vice-versa with
detector B and slit B. However, with the wires in place, some photons
are scattered, indeed some photons which passed through slit A will
arrive at detector B. With both slits open, and the wire placed
exactly at a null point of the interference pattern, the photons
passing through slit A and arriving at detector B exactly counteracts
the photons passing thoguh slit B that have been lost through
scattering. The mathematics of quantum mechanics assures this,
coincidental this may seem.
It may be a question of "interpretations of interpretations of QM",
however on the basis of the New Scientist article, I don't believe
Afshar have shown a problem with the complementarity principle.
Cheers
--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
A/Prof Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile)
UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 (")
Australia[EMAIL PROTECTED]
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Re: Shahriar S. Afshar Quantum Rebel (2)
We discussed Afshar's experiment before. Kathryn Cramer, the blogger, is John Cramer's daughter. John Cramer invented the Transactional Interpretation of QM, similar in flavor to Bohm's pilot wave theory, and his daughter is pushing Afshar's results as being best understood in the context of the TI. Actually she goes further and claims that Afshar falsifies both the Many-World and the Copenhagen Interpretations. The CI is not falsifiable IMO because it is too vague and amounts to little more than a policy of not asking embarrassing questions. Physicists can get their work done and leave philosophizing to others. The problem the Transactional Intepretation has with the MWI is that worlds in the MWI never fully disengage. There is always an exponentially decreasing connection between them. This means that the quantum formalism would reflect the actions of intelligent beings in shadow worlds who are different from ourselves, if we calculated to enough precision. This is true even in the TI or in Bohm's theory. Those theories may deny the reality of other worlds, but in principle they have to take into consideration what would be happening there in order to make their calculations. This is obvious in a double slit experiment, but the phenomenon never goes away completely, no matter how far we go towards decoherence. Let Schrodinger's cat become alive or dead, but suppose there is some super-advanced technology that can reverse the process of death at the quantum level, undo the decoherence and restore a coherent state. Now, even the TI has to take into consideration the actions of those in the other world who performed that technological miracle. This may seem too far-fetched even to consider, but we are taking tiny steps today in this direction, pushing farther into the decoherence frontier. So far everything suggests that QM holds up, meaning that interference is still detectable with proper experimental setup even after substantial amounts of decoherence. All the MWI says is that this effect, which is exactly what is predicted by standard QM, will persist even as decoherence advances so far that we can no longer measure the interference. Either an interpretation has to accept the reality of parallel worlds, making it a version of the MWI; or predict that this effect will no longer occur, which will violate QM; or deny that the people in the shadow worlds are real, even though the ripples of their actions affect our own world; or it has to stick its head in the sand and deny that it matters since we can't detect those ripples anyway today, and probably will never be able to do so. I'd be curious to know which choice the Transactional Interpretation makes. Hal Finney
Shahriar S. Afshar Quantum Rebel (2)
Comments (rants, peals of laughter)?: http://www.kathryncramer.com/wblog/archives/000674.html http://www.kathryncramer.com/wblog/archives/000530.html http://64.233.161.104/search?q=cache:AN9UxmCda50J:faculty.washington.edu/jcramer/PowerPoint/Boskone_0402.ppt++Afshar+experiment&hl=en Cheers! CMR<- insert gratuitous quotation that implies my profundity here ->
