A proposed double slit experiment to test for "hidden" variables
Jay R. Yablon
This follows up on some earlier threads I started with regard to the
double slit experiments. I would like to propose a real experiment
which may give us some answers about wave versus particle, hidden
variables, superluminality, and some other questions which go to the
heart of quantum theory. The experiment is a standard double-aperture
experiment, which is schematically illustrated at the link below:
http://home.nycap.rr.com/jry/Papers/Experiment.pdf
The standard experiment is modified in two ways. First, each aperture
can be opened or closed at will, very, very rapidly. A movable physical
barrier is one approach, but some of today's electronically-activated
LCD-type materials which can be made opaque or transparent quickly and
at will may also fit the bill. Second, there is a very precise timer
driving these apertures, responsive to when a photon, electron, etc. is
released from a source, one quantum at a time. Now, let me explain the
experiment and the theory it is intended to falsify or not.
1. As I have discussed in some of the previous threads, what we observe
in one-quantum-at-a-time double aperture (slit or pinhole) experiments
is that the detector registers one point-like "strike" on the detector
at a time, see, e.g.,
http://en.wikipedia.org/wiki/Image:Double-slit_experiment_results_Tanamura_2.jpg .
2. If we are being truly dispassionate and discarding all preconception
in describing the evidence of what is observed, we would have to say the
following:
a) each "strike" which appears on the detector appears one point at a
time, confined to a highly-localized "pinpoint."
b) nobody has ever fired a single quantum, and then detected it going
through BOTH apertures at once. Nor has anybody ever fired a single
quantum, and observed it hit the detector over any range beyond such a
single, highly-localized "pinpoint."
c) any "wave" patterns which have ever been observed on a detector --
either in a single or a double aperture experiment -- are *aggregate*
patterns which only appear following the buildup of large number of
individual "strikes" on the detector.
d) the aggregate "wave" pattern from multiple strikes when both
apertures remain open (the so-called "interference" pattern), is
decidedly different from the "wave" pattern which emerges if one
aperture is closed half of the time, and then the other aperture is
closed the other half of the time (two "single-aperture diffraction"
patterns).
e) *assuming* that we cannot know in advance where on the detector a
particular quantum will end up when fired, any such "wave" patterns
represent the probability that the particular quantum will end up at a
certain position on the detector.
3. If one wishes to try to explain WHY a particular quantum ends up
wherever it does on the detector, either in single or double aperture
experiments, one approach is to regard the "vacuum" through which the
quantum travels as a sort of "black box" which causes that quantum to
end up where it does based on whatever that quantum encounters while it
travels through the black box vacuum. Of course, this requires that one
view the vacuum not as an empty space, but rather, as a medium of real
physical interest within which real, energetic physical phenomenon are
occurring on the smallest scale. This is not an unreasonable view, and
is one which the author will adopt as a hypothesis to be falsified or
not by the experiment to be proposed here.
4. Observation 2) d) above, combined with hypothesis 3), leads to the
corollary that the black box vacuum must be "configured" differently
when both apertures are open, versus when one or the other aperture is
closed, so as to cause the individual quanta to distribute differently
for one versus the other circumstance. That is, the state of the
apertures determines the state of the vacuum which in turn determines
"strike position" of the quantum.
5. To all of the above, let us add without elaboration, the further
"hypothesis" that no physical signal may travel faster than the speed of
light. Combined with 4), this means that if one opens or closes an
aperture, the "news" of that aperture having been opened or closed
cannot propagate faster than the speed of light.
This gives us all the ingredients of the experiment, which is conducted
as follows:
6. Fire one quantum at a time towards the detector. Use electrons, all
of which must be fired at the "same" velocity v, to very close
tolerance. The reason for choosing electrons rather than photons is
because they travel slower than the speed of light, and so make it
possible to overcome the "signal propagation" problem discussed below.
7. Before each quantum is fired, start with both apertures closed.
When the quantum approaches the illustrated distance less than L from
the grating, open each aperture, based on a timer actuator which
calculates the time t after the firing based on the distance D = vt as
illustrated. In other words, opening the apertures is NOT based on
*detecting* the electron at distance <L, but is based on the *timing* of
knowing when the electron was fired and how much time must elapse for
the electron to come within <L of the grating.
8. Important note: It is recognized that the timing / actuation must
be done in a sophisticated way, because the signal indicating that the
electron has been fired must reach the timer actuator before the
electron reaches <L, and the timer actuator must in turn cause the
apertures to open just as the electron enters the <L region based on
this timing calculation. This is the "signal propagation" problem
referenced above. If photons were to be used rather than electrons,
while uniform velocity would naturally be achieved, there would be no
way for the signal that the photon has been fired to open the apertures
before the photon reached the apertures because then that signal that
the photon has been fired would have to arrive at the apertures, in the
form of their actuation, before the photon gets there, which is
materially impossible. With electrons, the signal that the electron has
been fired, which causes the apertures to open at a suitable time
thereafter, can in theory, and with some clever design of the
experimental apparatus, be arranged to "beat the electron" to the
apertures.
9. The apertures are spaced from each other by a distance greater than
2L.
10. Prediction: although both apertures are open at the time each
electron reaches the grating, what will build up over time on the
detector will be two separate single-aperture diffraction patterns, and
NOT the expected interference pattern.
11. Rationale for prediction: if each electron ends up where it does
on the detector as the result of the black box vacuum, see 3), and if
the black box vacuum is "configured" dependent upon the state of the
apertures, i.e., the vacuum is in a different state for an open aperture
versus a closed aperture, see 4), and if no signal may travel faster
than light, see 5), then the "news" that an aperture has been opened (or
closed) will transmit through the vacuum at no faster than the speed of
light. Thus, went the electron reaches the <L position based on timing
in relation to firing, the apertures change from closed to opened.
Suppose the electron goes through the top aperture. The electron will
reach and pass through the top aperture *before* the news that the
bottom aperture has opened can reach the top aperture, because the
apertures are spaced apart at >2L. Therefore, the vacuum which the
electron encounters when it passes through the top aperture will still
represent the "old news" that the bottom aperture is closed, and so the
electron will pass through the top aperture and strike the detectors as
it would in a single-aperture diffraction experiment, not a
double-aperture interference experiment. Ditto, but all vice-versa, for
the electron passing through the bottom aperture.
12. The main point of the experiment, is to have the electron pass
through one aperture, before the "news" that the other aperture has
opened reaches any part of the vacuum through which the electron travels
on it way to the detector. We are effectively "fooling" the electron
into "thinking" that it is partaking in a single-aperture experiment,
because the news that it is really involved in a double aperture
experiment does not have time to reach any part of the vacuum through
which the electron is traveling.
13. The reverse is also possible: fool the electron into thinking it is
part of a double rather than a single slit experiment, but with caveat.
Start with both apertures open. Close the bottom aperture only, at <L.
If the electron was headed through the bottom aperture, nothing will
happen because it will be blocked. If the electron goes through the top
aperture, the "old news" at the top aperture will tell the electron that
it is part of a double slit experiment, even though the bottom aperture
will have closed by the time the electron passed through the top
aperture. An interference pattern is then to be expected even though at
the time of passage, the experiment was a single aperture experiment.
The caveat: all of the electrons which reach the detector will have
passed only through the top slit, while in an ordinary interference
experiment, roughly half will have passed through each slit.
14. To overcome the caveat, use 13) as the first half of the
experiment. In the second half, start with both apertures open, and
close the top aperture only, at <L. After both halves of the experiment
are performed, we should then see another . . .
15. Prediction: although only one aperture is open at the time each
electron reaches the grating, what will build up over time on the
detector will be a two-aperture interference pattern, and NOT the
expected two separate diffraction patterns.
If these predictions come to pass, this would give credence to the view
that light consists of individual particles, that the place where any
single particle of light ends up on the detector is determined by the
configuration of the black box vacuum which that particle has passed
through, that the configuration of the vacuum is in turn determined by
the state of the apertures on the grating, and that information about
the state of the apertures can only propagate through the vacuum at up
to light speed.
The one question remaining then, is: how do the state of the apertures
on the grating cause the vacuum to become reconfigured? In an earlier
post, I hypothesized that a mechanism like that of Casimir, is a
plausible candidate for the physical agent of the aforementioned,
hypothesized phenomena.
Have fun!
Jay.
_____________________________
Jay R. Yablon
Email: jya...@nycap.rr.com
Web site: http://home.nycap.rr.com/jry/FermionMass.htm
Co-moderator, sci.physics.foundations
Jay R. Yablon
problem in the note of point 8, which should enable this experiment to
be performed with photons as well as than electrons. It is actually
quite simple.
Place the timer close to the grating. Place a "trigger" halfway between
the source and the timer. By activating the trigger, send a signal to
both the source to fire a photon, and to the timer to tell it that the
photon has been fired. When the signal reaches the timer, that means
the photon has been fired at the same instant. Then, the timer can send
a signal to change the state(s) of the apertures, and cause the aperture
state(s) to be changed, just before the photon arrives.
Oh No
>
>
>This gives us all the ingredients of the experiment, which is conducted
>as follows:
>
Feynman uses to explain quantum theory. In this case the electrons are
detected by scattering photons from a laser just AFTER the slits, but
before the formation of the interference pattern. It is then possible in
principle to alter the pattern from interference to no interference by
switching the detector on after the electron has passed beyond the
slits. Of course technically a bit tricky in this instance, but we do
much the same thing in the Aspect experiment, using a random number
generator to decide on the orientation of spin detection after the
production process of the entangled pair.
>
>10. Prediction: although both apertures are open at the time each
>electron reaches the grating, what will build up over time on the
>detector will be two separate single-aperture diffraction patterns, and
>NOT the expected interference pattern.
No. This is wrong. If both slits are open with no means of detection for
which one the electron passes through, then you get an interference
pattern.
>If these predictions come to pass, this would give credence to the view
>that light consists of individual particles, that the place where any
>single particle of light ends up on the detector is determined by the
>configuration of the black box vacuum which that particle has passed
>through, that the configuration of the vacuum is in turn determined by
>the state of the apertures on the grating, and that information about
>the state of the apertures can only propagate through the vacuum at up
>to light speed.
The predictions are against the laws of quantum theory, and have been
tested, notably in the Aspect experiment. They are wrong.
>
>The one question remaining then, is: how do the state of the apertures
>on the grating cause the vacuum to become reconfigured? In an earlier
>post, I hypothesized that a mechanism like that of Casimir, is a
>plausible candidate for the physical agent of the aforementioned,
>hypothesized phenomena.
Think about the fact that space as we understand it is itself the result
of measurement processes. The principle that the structure of space
depends upon the structure of matter is very clearly encapsulated in
Einstein's field equation. It is also contained in the Young's slits
experiment. The question "which slit" makes no sense unless space has a
structure in which it makes sense. Space only has a structure in which
this question makes sense if the interactions of matter allow us to
determine (in principle) which slit the electron came through.
Regards
--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email
Ken S. Tucker
> In reference to my original post, I just figured out how to overcome the
> problem in the note of point 8, which should enable this experiment to
> be performed with photons as well as than electrons. It is actually
> quite simple.
>
> Place the timer close to the grating. Place a "trigger" halfway between
> the source and the timer. By activating the trigger, send a signal to
> both the source to fire a photon, and to the timer to tell it that the
> photon has been fired. When the signal reaches the timer, that means
> the photon has been fired at the same instant. Then, the timer can send
> a signal to change the state(s) of the apertures, and cause the aperture
> state(s) to be changed, just before the photon arrives.
>
> Jay.
> _____________________________
> Jay R. Yablon
That's a hell of an interesting idea.
What's spawns in my mind is a camera shutter
together with an electron tube mechanism
(complete with an attracting anode) or otherwise
a photon source.
So I suggest, in place of the "trigger" mechanism,
a shutter that depends on time, close-open,
close-open etc. In electronics the ratio of close
to open is termed "duty cycle", and is basically
a "square wave", but you can make it a sinsodial
oscillation.
Now what happens is we're using the theory of
Amplitude Modulation, or equivalently, mixing
through a process of hetrodyning, (it's hard to
distinguish the two), to create "Side Bands".
That's the basis of SSB (Single Side Band) radio,
the theory of which is available.
What I capture is the possiblity of equating the
SSB and/or AM with a pair of slits.
Here's my understanding. We can use a single slit,
with an oscillating shutter, to produce the same
inteference pattern as a spatially static double slit.
Allow me to push this a bit, the equivalent of a
static double slit in space is the same as an
oscillating slit in time, that's my conjecture.
The phenomena creating such an interference
pattern varies in space as well as time because
of that conjecture. That makes sense, because
the interference pattern appears to me to be
covariant, IOW's the pattern ratio's are independant
of the FoR. (FoR = Frame of Reference).
Regards
Ken
Jay R. Yablon
news:Wjx2uMElhQ+FFw$+...@charlesfrancis.wanadoo.co.uk... . . .
>
>>
>>10. Prediction: although both apertures are open at the time each
>>electron reaches the grating, what will build up over time on the
>>detector will be two separate single-aperture diffraction patterns,
>>and
>>NOT the expected interference pattern.
>
> No. This is wrong. If both slits are open with no means of detection
> for
> which one the electron passes through, then you get an interference
> pattern.
>
>
> The predictions are against the laws of quantum theory, and have been
> tested, notably in the Aspect experiment. They are wrong.
>>
Perhaps I should start with a more basic question: has this experiment
or something similar ever been done before? Aspect tests entanglement
and superluminal information transfer as between two particles. My
proposed experiment produces a single particle at a time, in a classic
interference setting, and never tries to detect anything about the
particle until it strikes the detector (at which time "position" is what
is tested).
Now, I may be predicting wrongly, but if that is the case, this
experiment would give further proof that information as been transmitted
faster than the speed of light because the electron would somehow "know"
that the other slit had opened or closed even though information about
that happening would not have had time to reach it.
Fundamental to EPR is that you are starting out at a single event,
sending some sort of information / particle out in opposite directions
which then are spacelike separated, and seeing what transpires as
between the spacelike-separated states. If you "do" something to one
state, and what you have "done" to that one state somehow can be deduced
from the other spacelike-separated state, then we know some superluminal
communication is occurring.
Here, that "EPR piece" of the experiment lies in opening both slits at
the same time, just before the electron travels through one (which one
we do not try to tell), in such a way that information about the second
slit opening would not have had time to reach the electron in any theory
which set the speed of light as an upper limit.
So, I guess what I am saying, is let's discard any predictions for the
moment, and simply perform the experiment and see what happens. We may
gain even further confirmation of quantum "spookiness" and superluminal
information transmission, rather than support for the hidden variables
toward which I confess a personal bias.
I don't think an experiment similar to the one I am proposing has been
done before, though I do not know this for certain and would like to
know. Again, my experiment, which is very simple, may test some things
that others have tested for, but would do so in what seems to me to be a
very different way. This can give us further data about the quantum
world which we do not have at present. I would certainly surrender my
stubborn theoretical bias against dice-playing and superluminosity to
whatever the experimental results demonstrate.
Jay.
Oh No
>"Oh No" <No...@charlesfrancis.wanadoo.co.uk> wrote in message
>news:Wjx2uMElhQ+FFw$+...@charlesfrancis.wanadoo.co.uk...
>> Thus spake Jay R. Yablon <jya...@nycap.rr.com>
>>>
>>>
>
>or something similar ever been done before? Aspect tests entanglement
>and superluminal information transfer as between two particles. My
>proposed experiment produces a single particle at a time, in a classic
>interference setting, and never tries to detect anything about the
>particle until it strikes the detector (at which time "position" is what
>is tested).
I wish I knew that it had. Unfortunately the only measurement I know
where the decision on the thing to be measured takes place after the
event is the Aspect experiment. In practice I think experimental
procedures may be too difficult with a "simpler" experiment. Ultimately
it makes no difference. One is still testing the behaviour of "collapse"
in quantum theory.
>
>Now, I may be predicting wrongly, but if that is the case, this
>experiment would give further proof that information as been transmitted
>faster than the speed of light because the electron would somehow "know"
>that the other slit had opened or closed even though information about
>that happening would not have had time to reach it.
As Feynman describes, the situation is worse. In principle you can have
the electron pass through the slits, then decide on whether to detect
it. If you decide to detect it, it will have always come through one
slit and there will be no interference pattern. If you decide not to
detect it, there will be an interference pattern.
>
>Fundamental to EPR is that you are starting out at a single event,
>sending some sort of information / particle out in opposite directions
>which then are spacelike separated, and seeing what transpires as
>between the spacelike-separated states. If you "do" something to one
>state, and what you have "done" to that one state somehow can be deduced
>from the other spacelike-separated state, then we know some superluminal
>communication is occurring.
What you have done cannot be deduced. Nonetheless, after the event, you
can compare what you did with the distant measurement and show they are
correlated.
>
>
>So, I guess what I am saying, is let's discard any predictions for the
>moment, and simply perform the experiment and see what happens. We may
>gain even further confirmation of quantum "spookiness" and superluminal
>information transmission, rather than support for the hidden variables
>toward which I confess a personal bias.
>
>I don't think an experiment similar to the one I am proposing has been
>done before, though I do not know this for certain and would like to
>know. Again, my experiment, which is very simple, may test some things
>that others have tested for, but would do so in what seems to me to be a
>very different way. This can give us further data about the quantum
>world which we do not have at present. I would certainly surrender my
>stubborn theoretical bias against dice-playing and superluminosity to
>whatever the experimental results demonstrate.
>
I don't think there is any way to do an experiment as you describe in
practice. However the predictions of the mathematical formalism are
shown in EPR, and that has been tested by Aspect et al.
Think more on what it means to say something has position. Even in the
macroscopic world, you cannot say where you are sitting unless you say
where with respect to other matter. "I am sitting on the chair". "The
chair is in the corner of the room" and so forth. As Descartes pointed
out something only has position by being in contact with other matter.
The same applies to a ball in flight, it is effectively in contact with
light reflecting off it. Quantum effects appear when that definition of
position breaks down. If there is no position, then nor can you talk of
superluminal communication.
Jay R. Yablon
> Thus spake Jay R. Yablon <jya...@nycap.rr.com>
>>"Oh No" <No...@charlesfrancis.wanadoo.co.uk> wrote in message
>>news:Wjx2uMElhQ+FFw$+...@charlesfrancis.wanadoo.co.uk...
>>> Thus spake Jay R. Yablon <jya...@nycap.rr.com>
>>Now, I may be predicting wrongly, but if that is the case, this
>>experiment would give further proof that information as been
>>transmitted
>>faster than the speed of light because the electron would somehow
>>"know"
>>that the other slit had opened or closed even though information about
>>that happening would not have had time to reach it.
>
> As Feynman describes, the situation is worse. In principle you can
> have
> the electron pass through the slits, then decide on whether to detect
> it. If you decide to detect it, it will have always come through one
> slit and there will be no interference pattern. If you decide not to
> detect it, there will be an interference pattern.
Ah, Charles, but there is the rub. First, nobody has ever been able to
detect an electron showing up at both slits. Let's be scientific and
stick closely to what we observe. Whenever this is tested, it shows up
at one or the other but not both. All of these hypothetical assertions
that the electron is passing through both slits unless one tries to
detect and then it only passes through one slit is tantamount to saying
"all the empirical evidence says that one thing is going on, but when I
am not looking, that which all the evidence shows is not going on, is
going on." This is so counter to scientific method that it is
breathtaking, though I recognize that this is what the craziness of
quantum mechanics pushes us to.
But even more, there is NOT an interference pattern from only *one*
electron. Each electron registers in a very localized, "pointlike" way.
The interference pattern only emerges when a large number of electrons
have been fired, even one at a time. How does one explain this? One
could suppose that the probability of where any single electron
registers on the detector is a *conditional* probability, so that if one
electron strikes in one place, the next electron is less likely to
strike in that same place. Just like we take one card out of the deck,
there are only 51 left. Now THAT would be entanglement, but I don't
know of anyone who thinks that this would be so. So, in some way, where
the electron strikes must be conditioned by the fact of whether there
are two slits or one. The question seems unavoidable, how does the
state of the slits get communicated to the electron so as to affect
whether it will land such that the aggregate pattern is or is not that
of interference? That is the issue I am trying to gather very direct
evidence about with this experiment, avoiding inference as much as
possible.
. . .
> Think more on what it means to say something has position. Even in the
> macroscopic world, you cannot say where you are sitting unless you say
> where with respect to other matter. "I am sitting on the chair". "The
> chair is in the corner of the room" and so forth. As Descartes pointed
> out something only has position by being in contact with other matter.
> The same applies to a ball in flight, it is effectively in contact
> with
> light reflecting off it. Quantum effects appear when that definition
> of
> position breaks down. If there is no position, then nor can you talk
> of
> superluminal communication.
I would agree with that. Take away position, and many other things
vanish at the same time. However -- and this is probably a separate
thread title "whither the ether?" -- I do believe that the "vacuum" is a
very lively place with a great deal of energetic phenomena transpiring
on the smallest scale, and that such phenomena DO provide physical
"event" references relative to which other happenings can be described.
Best,
Jay.
Oh No
Quite, I did not say otherwise.
>All of these hypothetical assertions
>that the electron is passing through both slits unless one tries to
>detect and then it only passes through one slit is tantamount to saying
>"all the empirical evidence says that one thing is going on, but when I
>am not looking, that which all the evidence shows is not going on, is
>going on." This is so counter to scientific method that it is
>breathtaking, though I recognize that this is what the craziness of
>quantum mechanics pushes us to.
And yet it is not so unreasonable if one starts from the purely
empirical point of view, as described below, which led Descartes to
relationalism, that position is a relationship created through contact
or, as I would say, interaction. When you are looking, i.e. when you are
detecting the electrons, you are introducing new interactions, new
relationships. Those relationships are the very thing which makes up the
structure of measured space. If you are not looking, i.e. the detector
is switched off, those interactions no longer take place and space does
not acquire structure.
>
>But even more, there is NOT an interference pattern from only *one*
>electron.
Indeed. We can only talk about probabilities, and probabilities are
themselves only an idea when you are just talking of one electron.
>Each electron registers in a very localized, "pointlike" way.
Quite. I think that is in itself a strong indication that the electron
itself is always point-like - but the locality condition in qed can be
read as a mathematical statement that the electron is always point-like.
Imv it is actually proof of the point-like nature of particles because
it is required in a relativistic model.
>The interference pattern only emerges when a large number of electrons
>have been fired, even one at a time. How does one explain this? One
>could suppose that the probability of where any single electron
>registers on the detector is a *conditional* probability, so that if one
>electron strikes in one place, the next electron is less likely to
>strike in that same place. Just like we take one card out of the deck,
>there are only 51 left. Now THAT would be entanglement, but I don't
>know of anyone who thinks that this would be so.
No. The probabilities here are more like when the card is always
replaced before you select the next one.
> So, in some way, where
>the electron strikes must be conditioned by the fact of whether there
>are two slits or one. The question seems unavoidable, how does the
>state of the slits get communicated to the electron so as to affect
>whether it will land such that the aggregate pattern is or is not that
>of interference? That is the issue I am trying to gather very direct
>evidence about with this experiment, avoiding inference as much as
>possible.
Imagine a Knex model. All the rods have particular lengths, so that the
model only fits together in certain ways. If you were to take out one
rod and put in one of a different length, you may also have to change
things far removed from the rod you switched. So it is with the
structure of space in a relationist model. Space as we conceive it is
put together from all the ways the interactions of particles fit
together to make up the structures we perceive. If we change one slit to
two slits we are changing the very structure of space time, and thus
changing the places where the electron can finally arrive. As for why
the result appears as a wave interference pattern one has to get into
the mathematics of such a structure. Essentially it comes from the
relativistic constraints one imposes on the structure. Hilbert space is
used to describe probabilities for measurement results at given time.
Through a change of basis we get coefficients e^-ixp. We have a
relativistic constraint, so that is replaced with e^i(Et-xp), and this
is a wave form. As a result it is found that the only way probabilities
can work in a covariant structure is such that they have the same form
as wave interference patterns.
If there is only one slit, or if the electron is detected, the structure
of space is "solid" enough to say it comes through one slit. If there
are two slits and no detection, then the structure of space does not
exist in the same way and it is impossible to say that it comes through
one or both slits.
> . . .
>> Think more on what it means to say something has position. Even in the
>> macroscopic world, you cannot say where you are sitting unless you say
>> where with respect to other matter. "I am sitting on the chair". "The
>> chair is in the corner of the room" and so forth. As Descartes pointed
>> out something only has position by being in contact with other matter.
>> The same applies to a ball in flight, it is effectively in contact
>> with
>> light reflecting off it. Quantum effects appear when that definition
>> of
>> position breaks down. If there is no position, then nor can you talk
>> of
>> superluminal communication.
>
>I would agree with that. Take away position, and many other things
>vanish at the same time.
Indeed. The tricky thing is to build a model in which position is not
assumed. It requires some delicacy and a great deal of precision, but it
can be done. The result is a single theory incorporating quantum
electrodynamics and general relativity.
>However -- and this is probably a separate
>thread title "whither the ether?" -- I do believe that the "vacuum" is a
>very lively place with a great deal of energetic phenomena transpiring
>on the smallest scale, and that such phenomena DO provide physical
>"event" references relative to which other happenings can be described.
But now you are veering away from your objective of being entirely
empirical. I have a problem with the very concept of "vacuum". I have
interactions between matter and matter, such as can be conserved, and I
hold that the same interactions take place whether they are observed or
not, but I don't see room for the concept of a vacuum, least of all a
lively vacuum. If it is lively, it is full of matter, and so it is not a
vacuum.
Ben Rudiak-Gould
> When you are looking, i.e. when you are
> detecting the electrons, you are introducing new interactions, new
> relationships. Those relationships are the very thing which makes up the
> structure of measured space. If you are not looking, i.e. the detector
> is switched off, those interactions no longer take place and space does
> not acquire structure.
I don't think this is a reasonable position to take here, because the
observed interference pattern depends on the geometry of the space through
which we didn't watch the particle travel.
-- Ben
Ben Rudiak-Gould
> [proposed experiment snipped]
I don't see what your experiment tests that isn't already covered by
delayed-choice experiments, where the wave/particle choice isn't made until
after it's gone through the slits. As far as I know experiments like this
have been carried out (and agreed with quantum mechanics, obviously).
But I'm more interested in talking about the metaphysics. You say elsewhere
in the thread that you have a theoretical bias against dice-playing and
superluminosity. Well, so do I, but I have an equally strong bias toward
believing that quantum mechanics is correct, in the sense that it correctly
predicts the outcome of experiments including yours. The reason in all three
cases is very similar, and is related to notions of simplicity. Special
relativity is a nice theory because it unifies things like time/space and
mass/energy/momentum. Aether theories would have you believe that nature
actually works in a more complicated way, in which those things are not
really elegantly unified but merely seem as though they are. I find that
impossible to believe. It's the same with quantum mechanics. The rule for
quantizing a classical theory is simple and elegant: you keep the classical
Lagrangian unchanged, but instead of finding the critical points of the
action, you do a wavelike sum over all configurations, which automatically
approximates the classical behavior for large actions for the same reason
that high-frequency light classically follows a critical-time rule. It's
impossible to escape the impression that this is exactly why the classical
variational principle worked in the first place. You seem to be proposing
that what's really happening is a conspiracy involving traditional
particles, and this nice unification of classical wave and particle dynamics
is an accident and not a fundamental truth at all. And your only reason for
believing this is that you can't see how to reconcile the nice principles of
quantum mechanics with the equally nice principles of special relativity and
determinism.
Well, I propose that you can't figure out how to reconcile them because
you're stupid. And so are we all. I think it's a terrible embarrassment for
the human race that no one figured out the concept of spacetime until the
experimental data practically rubbed their noses in it. There were hundreds
of years there after Newton for someone to think of it. Even armed with
Maxwell's equations they all sat there drooling out of the corners of their
mouths and saying, well, sure, we can set up these false coordinate systems,
but they're obviously not physically sensible; now where is that darned
aether wind? Even the smartest people in the world are not very good at
noticing the obvious. So I think that all these elegant principles coexist
in some way that we'll all kick ourselves later for not figuring out, except
for the person who does figure it out, who hopefully will have frizzy hair
and insightful opinions about world politics so that we'll have another
useful figurehead for physics for the next hundred years.
-- Ben
Jay R. Yablon
news:etd3jk$kcl$1...@gemini.csx.cam.ac.uk...
> Jay R. Yablon wrote:
>> [proposed experiment snipped]
>
> I don't see what your experiment tests that isn't already covered by
> delayed-choice experiments, where the wave/particle choice isn't made
> until after it's gone through the slits. As far as I know experiments
> like this have been carried out (and agreed with quantum mechanics,
> obviously).
Ben,
This is a bit different, because a) we are not detecting or in any way
disturbing the electron until it strikes the detector at the very end,
and b) we are choosing the slit configuration at the very last instant
before the electron goes through the grating and not giving any
subluminal or luminal signal -- if there is one -- to get to the
electron and tell the electron how both slits are configured. If you
think about it closely, I don't think the experiments you refer to are
testing for quite the same things in quite the same way.
Just curious --
Do you think the predictions 10) and 15) I made in the experiment
description are the ones that we would see, or, as Charles suggests,
that we would see the opposite result?
Jay.
Oh No
It is an assumption of usual formulations that the wave function must be
defined in terms of the geometry of space, assumed as a prior. That
assumption leads to all the well documented problems of interpretation
in quantum theory. The relational viewpoint does not allow that
assumption. It expresses fundamental behaviour, and the structure of
space, in terms of interactions of particles, not the other way about.
The probabilities of measurement results are constrained by covariance
considerations not by wave effects. It happens that the resulting
patterns are the same as interference patterns, but in this model they
are not caused by wave interference, and nor is it possible to say the
particle travels through space.
Oh No
I don't see that. The classical variational principle works on the same
basis as "think of a number.. take away the number you first thought
of.. the answer is...". Introduce something physically meaningless,
eliminate it, and get back to a neat formulation of what you had in the
first place.
> You seem to be proposing that what's really happening is a conspiracy
>involving traditional particles, and this nice unification of classical
>wave and particle dynamics is an accident and not a fundamental truth
>at all. And your only reason for believing this is that you can't see
>how to reconcile the nice principles of quantum mechanics with the
>equally nice principles of special relativity and determinism.
>
>Well, I propose that you can't figure out how to reconcile them because
>you're stupid. And so are we all. I think it's a terrible embarrassment
>for the human race that no one figured out the concept of spacetime
>until the experimental data practically rubbed their noses in it. There
>were hundreds of years there after Newton for someone to think of it.
>Even armed with Maxwell's equations they all sat there drooling out of
>the corners of their mouths and saying, well, sure, we can set up these
>false coordinate systems, but they're obviously not physically
>sensible; now where is that darned aether wind? Even the smartest
>people in the world are not very good at noticing the obvious. So I
>think that all these elegant principles coexist in some way that we'll
>all kick ourselves later for not figuring out, except for the person
>who does figure it out, who hopefully will have frizzy hair and
>insightful opinions about world politics so that we'll have another
>useful figurehead for physics for the next hundred years.
The most stupid part of it the way in which we reject what the least
stupid people have had to say on the matter. Descartes and Leibniz laid
the conceptual basis from which Gauss and Riemann developed non-
Euclidean geometry. Einstein's special principle of relativity
incorporates only a part of Descartes and Leibniz fundamental
conception. Dealing correctly and mathematically with the notion
requires an understanding of many valued logics and of linear algebra
which was not available until the C20th, yet Von Neumann, one of the
greatest mathematicians in history, is largely ignored by the physics
establishment. Establishing that the relational viewpoint is correct
also requires QED, which has only been available for not much more than
50 years. However, from that point onwards, all the elements have been
in place. Really there should have been a great interest in putting them
together and completing the mathematical structure to describe Descartes
original relational position. Instead physicists are dismissive. They
say "that hasn't produced results so we don't believe it can produce
results" and work is stifled. At the same time they carry out
mathematical operations which any competent first year maths
undergraduate knows are not legitimate, changing orders of integration
where they cannot be changed and arbitrarily subtracting off the
resulting infinity, using arguments like
1+infinity+infinity^2..=1/(1-infinity) = 0.
That is stupid. If one cannot pass one's exams without first accepting
such arguments, then it is no wonder that the people who rise to the top
of the field are not capable of noticing the obvious.
Oh No
>news:etd3jk$kcl$1...@gemini.csx.cam.ac.uk...
>> Jay R. Yablon wrote:
>>> [proposed experiment snipped]
>>
>> I don't see what your experiment tests that isn't already covered by
>> delayed-choice experiments, where the wave/particle choice isn't made
>> until after it's gone through the slits. As far as I know experiments
>> like this have been carried out (and agreed with quantum mechanics,
>> obviously).
>
>Ben,
>
>This is a bit different, because a) we are not detecting or in any way
>disturbing the electron until it strikes the detector at the very end,
>and b) we are choosing the slit configuration at the very last instant
>before the electron goes through the grating and not giving any
>subluminal or luminal signal -- if there is one -- to get to the
>electron and tell the electron how both slits are configured. If you
>think about it closely, I don't think the experiments you refer to are
>testing for quite the same things in quite the same way.
I agree with Ben. A delayed choice experiment does test for the same
thing. Actually more so, because the decision is made after the electron
has passed the slits. What I am not sure about is whether experiments
like this have actually been done. If they have, then I am quite sure
they agree with quantum mechanics. My belief, however, is that such
experiments with electrons are not practicable. My belief is the same
with regard to your thought experiment. The timescales and distances
involved are just too short to allow anyone to build an apparatus that
can behave like this. If such an experiment has been done, I suspect it
involves something like trapping a photon in an optic fibre, or rather
in two optic fibres, of sufficient length to allow the decision to be
made before the photon emerges at the other end, where the interference
pattern is to be detected.
In practice I think the idea behind the EPR experiment was to devise an
instance where the experimental difficulties would not be
insurmountable. The Aspect experiment is the only one of which I know
where delayed choice is involved. It does not test for what is happening
in the simple instance of a two slit experiment, but it does test an
instance of the same mathematical structure and finds in favour of the
mathematical structure of quantum mechanics. The primary advantage of a
delayed choice two slit experiment, if such a thing has been done, would
be pedagogical rather than mathematical. In my view that advantage would
be well worth the trouble and expense of trying to do the experiment. As
I say, I think the use of optic fibres would be necessary for a
practical implementation of this test. I have no knowledge that it has
been done, and would be very interested to hear if it has.
harry
Right. But IMO in a weaker form it's still correct: If you are looking, the
structure of "space" is affected.
Harald
harry
> Jay R. Yablon wrote:
>> [proposed experiment snipped]
>
> I don't see what your experiment tests that isn't already covered by
> delayed-choice experiments, where the wave/particle choice isn't made
> until after it's gone through the slits. As far as I know experiments like
> this have been carried out (and agreed with quantum mechanics, obviously).
>
> But I'm more interested in talking about the metaphysics.
The discussions here are to focus on efforts to bring more metaphysics into
the realm of physics, if I understand it correctly.
> You say elsewhere in the thread that you have a theoretical bias against
> dice-playing and superluminosity. Well, so do I, but I have an equally
> strong bias toward believing that quantum mechanics is correct, in the
> sense that it correctly predicts the outcome of experiments including
> yours. The reason in all three cases is very similar, and is related to
> notions of simplicity. Special relativity is a nice theory because it
> unifies things like time/space and mass/energy/momentum. Aether theories
> would have you believe that nature actually works in a more complicated
> way, in which those things are not really elegantly unified but merely
> seem as though they are. I find that impossible to believe.
Instead, special relativity was designed to be about physics only, avoiding
metaphysics (similar to quantum mechanics). And even with physics, for a
long time people found it impossible to believe that planetary trajectories
are not cirles but ellipses - not elegant enough to their taste...
> It's the same with quantum mechanics. The rule for quantizing a classical
> theory is simple and elegant: you keep the classical Lagrangian unchanged,
> but instead of finding the critical points of the action, you do a
> wavelike sum over all configurations, which automatically approximates the
> classical behavior for large actions for the same reason that
> high-frequency light classically follows a critical-time rule. It's
> impossible to escape the impression that this is exactly why the classical
> variational principle worked in the first place. You seem to be proposing
> that what's really happening is a conspiracy involving traditional
> particles, and this nice unification of classical wave and particle
> dynamics is an accident and not a fundamental truth at all. And your only
> reason for believing this is that you can't see how to reconcile the nice
> principles of quantum mechanics with the equally nice principles of
> special relativity and determinism.
That reminds me of the "conspiracy" in QM which happens to be the topic of
this thread: it appears that there is a conspiracy against determining the
true nature of elementary particles when in transit. But does that make you
reject QM?
> Well, I propose that you can't figure out how to reconcile them because
> you're stupid. And so are we all. I think it's a terrible embarrassment
> for the human race that no one figured out the concept of spacetime until
> the experimental data practically rubbed their noses in it.
If you mean Minkowski's concept that space and time are of the same nature,
I think that that is an erroneous concept, the result of a confusion between
mathematics and physics. I even suspect that it played a role in the
embarrassing situation that after all these years we are still clueless as
to "what really happens".
> There were hundreds of years there after Newton for someone to think of
> it. Even armed with Maxwell's equations they all sat there drooling out of
> the corners of their mouths and saying, well, sure, we can set up these
> false coordinate systems, but they're obviously not physically sensible;
> now where is that darned aether wind? Even the smartest people in the
> world are not very good at noticing the obvious.
In retrorespect, Ives demonstrated that such an observation is impossible if
we assume conservation of energy and momentum. Calling what naturally
follows a conspiracy is a bit overdone ,don't you agree?
> So I think that all these elegant principles coexist in some way that
> we'll all kick ourselves later for not figuring out, except for the person
> who does figure it out, who hopefully will have frizzy hair and insightful
> opinions about world politics so that we'll have another useful figurehead
> for physics for the next hundred years.
Very right. Of course it may be that it already happened, but that nobody
listened. For good new ideas the time and circumstances must be right.
Harald
Oh No
>What I am not sure about is whether experiments like this have actually
>been done. If they have, then I am quite sure they agree with quantum
>mechanics.
In fact such experiments have been done. There is a good description in
wiki
http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser
The details, and the results are really quite interesting. It is even
possible to recover two interference patterns from no interference
pattern by correlating the results with stored information about the way
in which path information has been lost, after the photons have been
detected on the screen.
See the wiki entry for more detail and references, and, for an
ultrabrief synopsis, the post I have sent to Alf Steinbach's
Experimental confirmation of quantum erasure thread.
I think, rather than discuss a thought experiment which cannot be done
in practice, it will be more productive to discuss the meaning and
implications of the quantum eraser experiment.
harry
> Thus spake Jay R. Yablon <jya...@nycap.rr.com>
>>"Ben Rudiak-Gould" <br276d...@cam.ac.uk> wrote in message
>>news:etd3jk$kcl$1...@gemini.csx.cam.ac.uk...
>>> Jay R. Yablon wrote:
>>>> [proposed experiment snipped]
>>>
>>> I don't see what your experiment tests that isn't already covered by
>>> delayed-choice experiments, where the wave/particle choice isn't made
>>> until after it's gone through the slits. As far as I know experiments
>>> like this have been carried out (and agreed with quantum mechanics,
>>> obviously).
>>
>>Ben,
>>
>>This is a bit different, because a) we are not detecting or in any way
>>disturbing the electron until it strikes the detector at the very end,
>>and b) we are choosing the slit configuration at the very last instant
>>before the electron goes through the grating and not giving any
>>subluminal or luminal signal -- if there is one -- to get to the
>>electron and tell the electron how both slits are configured. If you
>>think about it closely, I don't think the experiments you refer to are
>>testing for quite the same things in quite the same way.
It sounds more straightforward than the Aspect experiment, but ususally in
practice there are some tricky problems that result in a less clearcut
result than what was proposed originally.
> I agree with Ben. A delayed choice experiment does test for the same
> thing. Actually more so, because the decision is made after the electron
> has passed the slits. What I am not sure about is whether experiments
> like this have actually been done. If they have, then I am quite sure
> they agree with quantum mechanics. My belief, however, is that such
> experiments with electrons are not practicable. My belief is the same
> with regard to your thought experiment. The timescales and distances
> involved are just too short to allow anyone to build an apparatus that
> can behave like this. If such an experiment has been done, I suspect it
> involves something like trapping a photon in an optic fibre, or rather
> in two optic fibres, of sufficient length to allow the decision to be
> made before the photon emerges at the other end, where the interference
> pattern is to be detected.
>
> In practice I think the idea behind the EPR experiment was to devise an
> instance where the experimental difficulties would not be
> insurmountable. The Aspect experiment is the only one of which I know
> where delayed choice is involved.
The Aspect experiment received some criticism, in particular by an expert in
statistics; but I never really understood the problem eventhough I asked the
expert by email. Now she has died, and my question remains. (Caroline
Thompson, see
http://en.wikipedia.org/wiki/Loopholes_in_Bell_test_experiments ).
> It does not test for what is happening
> in the simple instance of a two slit experiment, but it does test an
> instance of the same mathematical structure and finds in favour of the
> mathematical structure of quantum mechanics. The primary advantage of a
> delayed choice two slit experiment, if such a thing has been done, would
> be pedagogical rather than mathematical.
For the discussions here "pedagogical" would be the main thing anyway -
getting a better grip on the metaphysics.
> In my view that advantage would
> be well worth the trouble and expense of trying to do the experiment. As
> I say, I think the use of optic fibres would be necessary for a
> practical implementation of this test. I have no knowledge that it has
> been done, and would be very interested to hear if it has.
What do you think will be the problem with using electrons? Technically it's
more cumbersome (one needs a vacuum), but is there another problem that you
see?
Regards,
Harald
Oh No
>> Well, I propose that you can't figure out how to reconcile them because
>> you're stupid. And so are we all. I think it's a terrible embarrassment
>> for the human race that no one figured out the concept of spacetime until
>> the experimental data practically rubbed their noses in it.
>
>If you mean Minkowski's concept that space and time are of the same
>nature, I think that that is an erroneous concept, the result of a
>confusion between mathematics and physics.
I am quite sure it is.
>I even suspect that it played a role in the embarrassing situation that
>after all these years we are still clueless as to "what really
>happens".
>
Indeed it does. It is of central importance in the failure of attempts
at constructive field theory obeying e.g. the Wightman axioms. Hilbert
space must be defined on three dimensions as a means of describing the
physical situation in terms of potential measurement results by a given
apparatus at given time. In such a formulation an interaction operator
is naturally defined as an operator on Hilbert space at time t to
Hilbert space at time t+dt. There is no problem with the linearity of
such an operator.
If one now replaces Hilbert space on three dimensions with one defined
on space-time then it immediately becomes impossible to define a linear
interaction operator, because there is no way to define the equal point
multiplication. It is both undefined and undefinable.
Oh No
>
>The Aspect experiment received some criticism, in particular by an expert in
>statistics; but I never really understood the problem eventhough I asked the
>expert by email. Now she has died, and my question remains. (Caroline
>Thompson, see
>http://en.wikipedia.org/wiki/Loopholes_in_Bell_test_experiments ).
Caroline used to live about two miles away from me in Wales. We only met
once, but had a few discussions on sci.physics in the days when it was a
reasonable forum. I confess that we did not see eye to eye on quantum
theory, but I am sorry to hear she has died.
The detection loop hole is that in experiments of this type not all the
particles are detected, and I think there are also random detections of
photons not related to the experiment, requiring the subtraction of
"accidentals". This opens the possibility that the test result is being
influenced by unfair procedures, and does not rigorously support the
results of quantum theory. I think it is accepted that the original
Aspect experiment did not produce clear enough results. I don't think
that is so of some of the repetitions of the experiment, though I am not
an expert. A strict formulation of quantum theory only discusses
relationships between initial measured states and final measured states
and has nothing to say about undetected states, so I am not sure that
the detection loophole is all it is cracked up to be.
>> It does not test for what is happening
>> in the simple instance of a two slit experiment, but it does test an
>> instance of the same mathematical structure and finds in favour of the
>> mathematical structure of quantum mechanics. The primary advantage of a
>> delayed choice two slit experiment, if such a thing has been done, would
>> be pedagogical rather than mathematical.
>
>For the discussions here "pedagogical" would be the main thing anyway -
>getting a better grip on the metaphysics.
I agree. It is much harder to think about entanglement. In my view the
essential problems are all contained in the Young's slits experiment.
>
>> In my view that advantage would
>> be well worth the trouble and expense of trying to do the experiment. As
>> I say, I think the use of optic fibres would be necessary for a
>> practical implementation of this test. I have no knowledge that it has
>> been done, and would be very interested to hear if it has.
>
>What do you think will be the problem with using electrons? Technically it's
>more cumbersome (one needs a vacuum), but is there another problem that you
>see?
It is a question of maintaining stable electron states for long enough
periods of time that one can meaningfully make after the event
decisions.
Cl.Massé
news: aHf7tCQG...@charlesfrancis.wanadoo.co.uk
> I agree. It is much harder to think about entanglement. In my view the
> essential problems are all contained in the Young's slits experiment.
The Young's slits experiment is actually another case of entanglement. The
only difference is there is a single particle, but its detections at both
slits are also correlated. The relevant variable isn't a spin 0, but a
number of particles 1. The interference pattern is only incidental since it
is easily explainable with a classical wave, its presence or absence is a
way to detect the particle at a hole without detector.
For me, the most simple and characteristic setup is the one I described in
another post, with only one particle and two position detectors.
--
~~~~ clmasse on free F-country
Liberty, Equality, Profitability.
Jay R. Yablon
news:45fc1392$0$7466$426a...@news.free.fr...
> "Oh No" <No...@charlesfrancis.wanadoo.co.uk> a écrit dans le message de
> news: aHf7tCQG...@charlesfrancis.wanadoo.co.uk
>
>> I agree. It is much harder to think about entanglement. In my view
>> the
>> essential problems are all contained in the Young's slits experiment.
>
> The Young's slits experiment is actually another case of entanglement.
> The
> only difference is there is a single particle, but its detections at
> both
> slits are also correlated.
Well, let's be careful here. Nobody has EVER done an experiment which
detects a single particle passing through both slits. Any time this has
ever been tried, the particle is always detected at one slit or the
other but not both. That is a strictly classical correlation which says
that a particle can be one place or another place but not both places.
The conventional wisdom is that when we don't try to detect at the
slits, the particle is then, perhaps, somehow, going through both slits.
But, if one sticks to strict empiricism, that is supposition. It says
that what I do observe, is not what happens when I don't observe.
Now to be fair, we also know that the *aggregate* pattern which emerges
on the detector will be different, depending on whether I do or do not
detect at the slit. But, by detecting at the slit, I am disturbing the
particle and therefore making a change to what happens subsequently.
>The relevant variable isn't a spin 0, but a
> number of particles 1. The interference pattern is only incidental
> since it
> is easily explainable with a classical wave, its presence or absence
> is a
> way to detect the particle at a hole without detector.
The *aggregate* interference pattern from *multiple* particles is
identical with that of a classical wave. "Easily explainable" is a very
different assertion. It is not at all easily explainable, how when one
does the Young experiment one particle at a time, the particles know to
form what is an interference pattern, but only in the aggregate. That
is, if we are to be very careful with our language, all we can say is
that the probability distribution for where each individual "strike" is
made on the detector happens to coincide with the classical wave
interference pattern. We can't say there is "interference." We can
only say that the probability forms an interference pattern as evidenced
by the pattern which arises from a large number of strikes on the
detector.
> For me, the most simple and characteristic setup is the one I
> described in
> another post, with only one particle and two position detectors.
Can you provide a pointer to that, please.
Jay.
Ken S. Tucker
...
> Can you provide a pointer to that, please.
> Jay.
LOL, yes, a LASER pointer.
Funny, I was studying this thread and it dawned on me
(for reasons unknown :-) that we own a "laser pointer".
We cut a tiny wedge like \/ in a piece of cardboard and
moved the laser up and down the wedge, (I put a clothes
peg on the pointer botton to keep it on), and we have a
white wall about 16' away to view the light pattern that
goes through the slit.
With the slit (\/) vertical, as the laser is moved to the
lower part of the slit the image expanded horizontally,
and consisted noticeably of dots.
We ruled out a "pin-hole" camera effect by varying the
distance from the laser to the slit, and that had little
observational effect. The LASER itself is not a pin-
point source though, but close enough.
So far what I've said is easily reproduced in your own
home, but what follows are our speculations.
The horizontal dot pattern that emerged near the
bottom of the wedge looked roughly like,
.... o o O o o ....
Being a single slit , the refractive index appears to depend
upon the density of the electron shell in the slit the photon
reacts with, and the cardboard slit having depth accounts
for the "...." at each end.
Next we employed a pair of steel scissors to form the \/
wedge. Subjectively the pattern appeared to become,
..... ooOOOoo.....
where steel has a deeper level of electron shells to
create the single slit refraction.
Our tentative conclusion, is that the one slit itself, because
of it's atomic electronic shell's, reacts with the photons,
via quantized refractive index, to produce the single slit
observed diffraction.
Best Regards
Ken S. Tucker
Cl.Massé
>> The only difference is there is a single particle, but its detections at
>> both slits are also correlated.
"Jay R. Yablon" <jya...@nycap.rr.com> a écrit dans le message de news:
563odlF...@mid.individual.net
> Well, let's be careful here. Nobody has EVER done an experiment which
> detects a single particle passing through both slits. Any time this has
> ever been tried, the particle is always detected at one slit or the
> other but not both. That is a strictly classical correlation which says
> that a particle can be one place or another place but not both places.
Yes, let's be careful. We can't say that a particle can *be* one place or
another, we can only say that the particle can *be detected* one place or
another. If not, we are making a hidden assumption.
> The conventional wisdom is that when we don't try to detect at the
> slits, the particle is then, perhaps, somehow, going through both slits.
No, the particle *is* nowhere. There is a *probability of detection* that
is a function of space.
> But, if one sticks to strict empiricism, that is supposition. It says
> that what I do observe, is not what happens when I don't observe.
Empiricism says that if the particle is detected at one slit, it is never
detected at the other slit, and by repeating the experiment, there is no
interference pattern. We observe a correlation between both slits, which is
expressed by the fact that the number of detection is never greater than
one. Now, by repeating the experiment, it is possible to know whether the
particle is always detected one time, or is never detected.
>> For me, the most simple and characteristic setup is the one I
>> described in another post, with only one particle and two position
>> detectors.
> Can you provide a pointer to that, please.
> > A particle in a spherical state is send from a point. Two detectors are
set up at the same distance from that point, but in opposite direction. As
soon as one detector fire, we know the other one can't, although no
information has been sent to it. < <
harry
>>> The Young's slits experiment is actually another case of entanglement.
>>> The only difference is there is a single particle, but its detections at
>>> both slits are also correlated.
>
> "Jay R. Yablon" <jya...@nycap.rr.com> a écrit dans le message de news:
> 563odlF...@mid.individual.net
>
>> Well, let's be careful here. Nobody has EVER done an experiment which
>> detects a single particle passing through both slits. Any time this has
>> ever been tried, the particle is always detected at one slit or the
>> other but not both. That is a strictly classical correlation which says
>> that a particle can be one place or another place but not both places.
>
> Yes, let's be careful. We can't say that a particle can *be* one place or
> another, we can only say that the particle can *be detected* one place or
> another. If not, we are making a hidden assumption.
Actually, and against my earlier suggestion, I guess we can be more
conclusive after reading "Origin of quantum-mechanical complementarity
probed by a 'which-way' experiment in an atom interferometer" by Duer et al,
Nature vol.395 (1988), p.33. It was not done with slits, but the experiment
does look similar. I think that we will have to agree that heavy atoms
follow a certain path, so that at least for such experiments there must have
been real "particles" in the ordinary sense of the word that really *were*
(or may supposed to have been!) at one place and not at another place.
If someone here has a different opinion, I would like to know it (and why!).
Note: I had forgotten about that paper until someone here probably mentioned
it (who and where?); in any case, I found it in my bag yesterday. :-))
>> The conventional wisdom is that when we don't try to detect at the
>> slits, the particle is then, perhaps, somehow, going through both slits.
>
> No, the particle *is* nowhere. There is a *probability of detection* that
> is a function of space.
As I argue above, for at least some experiments there can be little doubt
that we are dealing with real particles that travel along one path only (and
even at only a few m/s in some cases).
Regards,
Harald
Oh No
>
>"Cl.Massé" <ret...@contactprospect.com> wrote in message
>news:45feb2ed$0$1276$426a...@news.free.fr...
>>>> The Young's slits experiment is actually another case of entanglement.
>>>> The only difference is there is a single particle, but its detections at
>>>> both slits are also correlated.
>>
>> "Jay R. Yablon" <jya...@nycap.rr.com> a écrit dans le message de news:
>> 563odlF...@mid.individual.net
>>
>>> Well, let's be careful here. Nobody has EVER done an experiment which
>>> detects a single particle passing through both slits. Any time this has
>>> ever been tried, the particle is always detected at one slit or the
>>> other but not both. That is a strictly classical correlation which says
>>> that a particle can be one place or another place but not both places.
>>
>> Yes, let's be careful. We can't say that a particle can *be* one place or
>> another, we can only say that the particle can *be detected* one place or
>> another. If not, we are making a hidden assumption.
>
>Actually, and against my earlier suggestion, I guess we can be more
>conclusive after reading "Origin of quantum-mechanical complementarity
>probed by a 'which-way' experiment in an atom interferometer" by Duer et al,
>Nature vol.395 (1988), p.33. It was not done with slits, but the experiment
>does look similar. I think that we will have to agree that heavy atoms
>follow a certain path, so that at least for such experiments there must have
>been real "particles" in the ordinary sense of the word that really *were*
>(or may supposed to have been!) at one place and not at another place.
>If someone here has a different opinion, I would like to know it (and why!)
Can't find that paper, but quantum mechanical behaviour does not depend
on mass. Interference is seen in a Young’s slits experiment using
Buckminster Fullerene, just as it is for photons or electrons, but
quantum mechanical behaviour is lost for hot Buckminster Fullerene which
radiates photons such that its path through a diffraction grating may be
tracked in principle (Hackermueller L., Hornberger K., Brezger B.,
Zeilinger A., Arndt M., 2004, Nature, 427, 711-714.)
>
>Note: I had forgotten about that paper until someone here probably mentioned
>it (who and where?); in any case, I found it in my bag yesterday. :-))
>
>>> The conventional wisdom is that when we don't try to detect at the
>>> slits, the particle is then, perhaps, somehow, going through both slits.
>>
>> No, the particle *is* nowhere. There is a *probability of detection* that
>> is a function of space.
>
>As I argue above, for at least some experiments there can be little doubt
>that we are dealing with real particles that travel along one path only (and
>even at only a few m/s in some cases).
These are particles such that the probability of detection is always on
that path. Claude is right. It does not follow that the particle ceases
to be a particle, but rather that it ceases to have a place.
harry
> Thus spake harry <harald.vanlin...@epfl.ch>
>>
>>The Aspect experiment received some criticism, in particular by an expert
>>in
>>statistics; but I never really understood the problem eventhough I asked
>>the
>>expert by email. Now she has died, and my question remains. (Caroline
>>Thompson, see
>>http://en.wikipedia.org/wiki/Loopholes_in_Bell_test_experiments ).
>
> Caroline used to live about two miles away from me in Wales. We only met
> once, but had a few discussions on sci.physics in the days when it was a
> reasonable forum. I confess that we did not see eye to eye on quantum
> theory, but I am sorry to hear she has died.
>
> The detection loop hole is that in experiments of this type not all the
> particles are detected, and I think there are also random detections of
> photons not related to the experiment, requiring the subtraction of
> "accidentals". This opens the possibility that the test result is being
> influenced by unfair procedures, and does not rigorously support the
> results of quantum theory. I think it is accepted that the original
> Aspect experiment did not produce clear enough results. I don't think
> that is so of some of the repetitions of the experiment, though I am not
> an expert.
One year ago I asked Nicolas Gisin about it (Geneva), and he stated that so
far no single experiment had managed to close simultaneously the detection
and the locality loophole. But then again, in view of the titles of some
papers, not everyone agreed with that.
> A strict formulation of quantum theory only discusses
> relationships between initial measured states and final measured states
> and has nothing to say about undetected states, so I am not sure that
> the detection loophole is all it is cracked up to be.
Loopholes imply that experimental results don't allow to draw solid
conclusions.
Regards,
Harald
Oh No
>> relationships between initial measured states and final measured states
>> and has nothing to say about undetected states, so I am not sure that
>> the detection loophole is all it is cracked up to be.
>
>Loopholes imply that experimental results don't allow to draw solid
>conclusions.
>
results of the Aspect experiment. A mathematical structure is defined
consistent with much simpler experimental evidence. This experiment
merely tests a logical deduction within that structure. If one wants to
understand the reasons why the structure should be correct, one has to
go to fundamental postulates and think about what they are saying.
Cl.Massé
news: 117457...@sicinfo3.epfl.ch
> Actually, and against my earlier suggestion, I guess we can be more
> conclusive after reading "Origin of quantum-mechanical complementarity
> probed by a 'which-way' experiment in an atom interferometer" by Duer et
> al, Nature vol.395 (1988), p.33. It was not done with slits, but the
> experiment does look similar. I think that we will have to agree that
> heavy atoms follow a certain path, so that at least for such experiments
> there must have been real "particles" in the ordinary sense of the word
> that really *were* (or may supposed to have been!) at one place and not
> at another place.
> If someone here has a different opinion, I would like to know it (and
> why!).
I have a different opinion, but it's up to me to ask. What makes you think
the atom follows a path? It is possible to describe everything without
using a path, and if you want to find out, the observation destroy the
interference pattern, so that it is no longer the same process.
The problem is, we think in terms of corpuscles and waves, with their
associated hidden assumptions. But none exists in Nature, they are only
human concepts. The particles aren't at the same time a corpuscle and a
wave, they are neither, they are something else, the truth is elsewhere.
harry
> "harry" <harald.vanlin...@epfl.ch> a écrit dans le message de
> news: 117457...@sicinfo3.epfl.ch
>
>> Actually, and against my earlier suggestion, I guess we can be more
>> conclusive after reading "Origin of quantum-mechanical complementarity
>> probed by a 'which-way' experiment in an atom interferometer" by Duer et
>> al, Nature vol.395 (1988), p.33. It was not done with slits, but the
>> experiment does look similar. I think that we will have to agree that
>> heavy atoms follow a certain path, so that at least for such experiments
>> there must have been real "particles" in the ordinary sense of the word
>> that really *were* (or may supposed to have been!) at one place and not
>> at another place.
>> If someone here has a different opinion, I would like to know it (and
>> why!).
>
> I have a different opinion, but it's up to me to ask. What makes you
> think
> the atom follows a path? It is possible to describe everything without
> using a path, and if you want to find out, the observation destroy the
> interference pattern, so that it is no longer the same process.
>
> The problem is, we think in terms of corpuscles and waves, with their
> associated hidden assumptions.
Well, that's exactly the thing. A heavy metal atom or a bucky ball is very
much what we commonly define as a "particle" or a "corpuscle", and which
normally has location as one of its defined characteristics. A differrent
opinion implies changing our definitions and understanding of ordinary
microscopic objects to something that looks magical. So, the question is,
are we looking at real magic or at a magician's trick?
Regards,
Harald
Cl.Massé
> Well, that's exactly the thing. A heavy metal atom or a bucky ball is very
> much what we commonly define as a "particle" or a "corpuscle", and which
> normally has location as one of its defined characteristics.
It has a location only in classical mechanics. In quantum mechanics, the
location is the result of a measurement.
harry
> "harry" <harald.vanlin...@epfl.ch> a écrit dans le message de
> news: 117490...@sicinfo3.epfl.ch
>
>> Well, that's exactly the thing. A heavy metal atom or a bucky ball is
>> very
>> much what we commonly define as a "particle" or a "corpuscle", and which
>> normally has location as one of its defined characteristics.
>
> It has a location only in classical mechanics. In quantum mechanics, the
> location is the result of a measurement.
That is one interpretation. Similar to Schrodinger's cat: are you only at a
certain location when that is measured? Can you prove that?
Cheers,
Harald
Cl.Massé
>> location is the result of a measurement.
"harry" <harald.vanlin...@epfl.ch> a écrit dans le message de
news: 1175073...@sicinfo3.epfl.ch
> That is one interpretation.
A little more than one interpretation.
> Similar to Schrodinger's cat: are you only at
> a certain location when that is measured?
It depends whether you measure the location or another quantity like
momentum. In the latter case, the particle is projected onto a state with
not well defined location.
> Can you prove that?
I can prove it for quantum mechanics as a theory. For reality, I can't
prove anything more than what is given by the known experimental results.
In the double slit experiment, we know that when the location is measured,
the interference fringes disappear. We are then forced to assume that the
particle has no well defined value of location when it isn't measured.
Peter
> "harry" <harald.vanlin...@epfl.ch> a écrit dans le message de
> news: 1175073...@sicinfo3.epfl.ch
> > Similar to Schrodinger's cat: are you only at
> > a certain location when that is measured?
Within Heisenberg's and equivalent quantum mechanics, the classical notion of
locus of a body is meaningless, within Bohmian wave mechanics not.
> I can prove it for quantum mechanics as a theory. For reality, I can't
> prove anything more than what is given by the known experimental results.
> In the double slit experiment, we know that when the location is measured,
> the interference fringes disappear. We are then forced to assume that the
> particle has no well defined value of location when it isn't measured.
This conclusion holds true only within those theories, where the classical
notion of locus is meaningless (cf. above).
You are arguing within Schrödinger's wave mechanics (or a part of it). This
theory describes particles that does *not* move along classical orbits. But
you (and most textbooks) are trying to apply the *classical* notions of locus
and momentum, of body and wave to these particles. It is only logical that
this runs into contradictions.
Good luck ;-)
Peter