FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Science and Technology » Physics » Research
Two-slit experiment
Post new topic   Reply to topic Page 1 of 3 [38 Posts] View previous topic :: View next topic
Goto page:  1, 2, 3 Next
Author Message
Jonathan Thornburg -- rem
science forum beginner


Joined: 06 May 2005
Posts: 41

PostPosted: Thu Jun 22, 2006 9:38 pm    Post subject: Re: Two-slit experiment Reply with quote

drspeg <drspeg@hotmail.com> wrote:
Quote:
I've been looking for an answer to two questions regarding the 2-slit
experiment (showing both wave and particle properties of light). I hope
someone here might know how to respond.
[[...]]
(1) Does obtaining an interference pattern depend at all on the timing of
the electron gun shooting each new electron? Or would the interference
pattern still obtain even if you shot one electron a day for many days (and
were able to record the impacts of electrons on the detector plate)?

Yes, you would still get an interference pattern. That is, the
(same) interference pattern is still there even at *arbitrarily low*
intensities (&& correspondingly long exposure times). I posted a
bunch of references on this to this newsgroup on 29.June.2001:
http://www.lns.cornell.edu/spr/2001-06/msg0033834.html

ciao,

--
-- "Jonathan Thornburg -- remove -animal to reply" <jthorn@aei.mpg-zebra.de>
Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
Golm, Germany, "Old Europe" http://www.aei.mpg.de/~jthorn/home.html
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam
Back to top
Uncle Al
science forum Guru


Joined: 24 Mar 2005
Posts: 1226

PostPosted: Fri Jun 23, 2006 3:22 am    Post subject: Re: Two-slit experiment Reply with quote

drspeg wrote:
Quote:

I've been looking for an answer to two questions regarding the 2-slit
experiment (showing both wave and particle properties of light). I hope
someone here might know how to respond.

Quick review of what I believe I know: Shooting a single photon (or
electron) at a wall that contains two slits will result in an interference
pattern on the wall (detector plate) beyond the holes. Blocking one hole
results in an accumulation pattern. When both holes are open, detecting
which of the two holes the electron passes through results in an
accumulation pattern (uncertainty is violated).

A double slit pattern is not the sum of two single slit patterns. For
one thing, the double slit maximum is directly opposite the center
barrier. You can look it up in a physics text book,

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
http://www.motionmountain.net/

Quote:
(1) Does obtaining an interference pattern depend at all on the timing of
the electron gun shooting each new electron? Or would the interference
pattern still obtain even if you shot one electron a day for many days (and
were able to record the impacts of electrons on the detector plate)?

Timing is irrelevant. Each individual moiety's wavefunction passes
through both slits - photon, electron, or huge giant really big
spatially extended rigidly multiply-connected massive lump,

http://www.quantum.univie.ac.at/research/matterwave/c60/index.html
C60 diffraction

Quote:
(2) If, in the case where one determines through which slit each electron
passes, one were to replace the detector plate with ANOTHER wall containing
two slits, would uncertainty be restored? That is, knowing through which
slit electrons first pass should produce an accumulation pattern, but if
that pattern were displayed on a wall containing two slits (in this case the
experimenter does NOT determine through which slit the electron passes)
would an interference pattern occur?

Google
"quantum eraser" 15,400 hits

But why stop there?

http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

Quote:
So, in this double-two-slit experiment, determining the first "choice" made
by the pasing electron, but not the second... would there be an accumulation
pattern followed by an interference pattern?

Here's a nice Gedankenexperiment. We take an organic molecule that
degenerately rearranges at a tremendous rate, like semibullvalene
(Ea=5.5 kcal/mol),

http://faculty.juniata.edu/reingold/rsch.html
http://en.wikipedia.org/wiki/Semibullvalene
<http://csi.chemie.tu-darmstadt.de/ak/immel/tutorials/structures/index5.html>

and we do the C60 experiment with it. However... when we thin-film
fabricate the diffraction grating we apply an alternating Peltier
heater so alternate slits are cold and hot. When a semibullvalene
wavefunction passes through the slits it has different rearrangement
rates at the different temperatures. Find a set of conditions that
dephases the wavefunction by exactly 180 degrees slit vs. slit. When
the two halves recombine on the other side... destructive
interference! Where is the molecule?

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf
Back to top
Igor Khavkine
science forum Guru


Joined: 01 May 2005
Posts: 607

PostPosted: Fri Jun 23, 2006 3:41 am    Post subject: Re: Two-slit experiment Reply with quote

Jonathan Thornburg -- remove -animal to reply wrote:
Quote:
drspeg <drspeg@hotmail.com> wrote:
I've been looking for an answer to two questions regarding the 2-slit
experiment (showing both wave and particle properties of light). I hope
someone here might know how to respond.
[[...]]
(1) Does obtaining an interference pattern depend at all on the timing of
the electron gun shooting each new electron? Or would the interference
pattern still obtain even if you shot one electron a day for many days (and
were able to record the impacts of electrons on the detector plate)?

Yes, you would still get an interference pattern. That is, the
(same) interference pattern is still there even at *arbitrarily low*
intensities (&& correspondingly long exposure times). I posted a
bunch of references on this to this newsgroup on 29.June.2001:
http://www.lns.cornell.edu/spr/2001-06/msg0033834.html

Here are a couple of other references:

http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm
http://www.hqrd.hitachi.co.jp/em/movie.cfm, number (2)

The first link describes a double slit experiment using a very low
emission electron gun. The second one shows a movie of how the
interference pattern is actually accumulated. The interference pattern
appears even when the electron gun essentially fires a single eletron
at a time.

Igor
Back to top
Alf P. Steinbach
science forum beginner


Joined: 26 May 2005
Posts: 10

PostPosted: Fri Jun 23, 2006 12:36 pm    Post subject: Re: Two-slit experiment Reply with quote

* Igor Khavkine:
Quote:
Jonathan Thornburg -- remove -animal to reply wrote:
drspeg <drspeg@hotmail.com> wrote:
(1) Does obtaining an interference pattern depend at all on the timing of
the electron gun shooting each new electron? Or would the interference
pattern still obtain even if you shot one electron a day for many days (and
were able to record the impacts of electrons on the detector plate)?
Yes, you would still get an interference pattern. That is, the
(same) interference pattern is still there even at *arbitrarily low*
intensities (&& correspondingly long exposure times). I posted a
bunch of references on this to this newsgroup on 29.June.2001:
http://www.lns.cornell.edu/spr/2001-06/msg0033834.html

Here are a couple of other references:

http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm
http://www.hqrd.hitachi.co.jp/em/movie.cfm, number (2)

The first link describes a double slit experiment using a very low
emission electron gun.

But are there experiments of good standing that directly rule out any
memory of past events in the detector, e.g. with hours between single
events, thermal randomization between events, or the like?

I think that that, not single particle at a time, was essentially what
the OP (drspeg <drspeg@hotmail.com>) asked.

The reference list directly provided by Jonathan didn't seem to provide
any such reference, and in fact, of the four URLs listed in that
article, the three last URLs didn't work (probably moved).

And although there were many follow-ups to the posting that Jonathans's
was a response to, all of these claiming an abundance of experimental
evidence, not one provided a reference to such an experiment. The
closest was perhaps <url:
http://www.ati.ac.at/~summweb/ifm/experiment/resultsf.html#top>. But
seemingly also that that was just another statistically-one-at-a-time
experiments.

Thus, my curiosity is pickled[1]! ;-)



[1] <url: http://www.invasioncreations.com/PickleCuriosity.swf>

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
Back to top
bz
science forum Guru


Joined: 24 Mar 2005
Posts: 833

PostPosted: Fri Jun 23, 2006 12:36 pm    Post subject: Re: Two-slit experiment Reply with quote

"drspeg" <drspeg@hotmail.com> wrote in
news:R62dnftk_8SSZQrZnZ2dnUVZ_qadnZ2d@libcom.com:

Quote:
I've been looking for an answer to two questions regarding the 2-slit
experiment (showing both wave and particle properties of light). I hope
someone here might know how to respond.

Quick review of what I believe I know: Shooting a single photon (or
electron) at a wall that contains two slits will result in an
interference pattern on the wall (detector plate) beyond the holes.

Wrong. A single photon will produce a single point response somewhere on
the detector plate. The probability of hitting any one point can be
determined by accumulating data from a series of single photons(or
electrons).

A series of single photons will build up a pattern similar to that seen
when a continuous stream of photons is used.


Quote:
Blocking one hole results in an accumulation pattern.

When one hole is blocked, and a series of single photons is used, the
accumulation pattern will look similar to that seen when a continuous
stream of photons is used with a single slit.

Quote:
When both holes
are open, detecting which of the two holes the electron passes through
results in an accumulation pattern (uncertainty is violated).

(1) Does obtaining an interference pattern depend at all on the timing
of the electron gun shooting each new electron? Or would the
interference pattern still obtain even if you shot one electron a day
for many days (and were able to record the impacts of electrons on the
detector plate)?

Appears to be rate independent. Photon(Electron) multiplyer arrays can be
used to capture and record the location of the impacts over a long period
of time.

Quote:

(2) If, in the case where one determines through which slit each
electron passes, one were to replace the detector plate with ANOTHER
wall containing two slits, would uncertainty be restored? That is,
knowing through which slit electrons first pass should produce an
accumulation pattern, but if that pattern were displayed on a wall
containing two slits (in this case the experimenter does NOT determine
through which slit the electron passes) would an interference pattern
occur?

Perform the experiment and see.

Quote:

So, in this double-two-slit experiment, determining the first "choice"
made by the pasing electron, but not the second... would there be an
accumulation pattern followed by an interference pattern?

Thanks!






--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
Back to top
Oz
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 155

PostPosted: Fri Jun 23, 2006 12:37 pm    Post subject: Re: Two-slit experiment Reply with quote

Igor Khavkine <igor.kh@gmail.com> writes
Quote:
The first link describes a double slit experiment using a very low
emission electron gun. The second one shows a movie of how the
interference pattern is actually accumulated. The interference pattern
appears even when the electron gun essentially fires a single eletron
at a time.

These are all very important experiments.

1) The self-interference of both photons and electrons (and much larger
things like fullerenes). These have all been demonstrated.

2) There is also the interference of two sources each going through one
slit **when intensity is so low that the probability of finding two
'photons' in the apparatus at the same time is very low.

Now this has been demonstrated for photons. However the laser light used
for each beam (separate lasers) had extremely long coherence lengths
(times). To do this with electrons might be problematic (ie
"challenging") but would be interesting. Anybody any ideas how it could
be done?

--
Oz
This post is worth absolutely nothing and is probably fallacious.
Back to top
Arkadiusz Jadczyk
science forum beginner


Joined: 02 May 2005
Posts: 21

PostPosted: Fri Jun 23, 2006 10:05 pm    Post subject: Re: Two-slit experiment Reply with quote

On Thu, 22 Jun 2006 06:42:15 +0000 (UTC), "drspeg" <drspeg@hotmail.com>
wrote:

Quote:
I've been looking for an answer to two questions regarding the 2-slit
experiment (showing both wave and particle properties of light). I hope
someone here might know how to respond.

Quick review of what I believe I know: Shooting a single photon (or
electron) at a wall that contains two slits will result in an interference
pattern on the wall (detector plate) beyond the holes.

Shooting one electron produces one dot. Not a pattern.


Quote:
Blocking one hole
results in an accumulation pattern.

Blocking one hole and shooting one electron will also produce just one
dot.


Quote:
When both holes are open, detecting
which of the two holes the electron passes through results in an
accumulation pattern (uncertainty is violated).

Probably when you wrote "shooting a single electron" you meant
"shooting one electron at a time, many times"?

Quote:
(1) Does obtaining an interference pattern depend at all on the timing of
the electron gun shooting each new electron?

Generally time of the shooting has nothing to do with the pattern.
Unless the detecting device has some large relaxation time etc.


Or would the interference
Quote:
pattern still obtain even if you shot one electron a day for many days (and
were able to record the impacts of electrons on the detector plate)?

The answer is "yes". But you should make changes to your apparatus
during the whole experiment.

Quote:
(2) If, in the case where one determines through which slit each electron
passes, one were to replace the detector plate with ANOTHER wall containing
two slits, would uncertainty be restored?

It is not clear to me what you have in mind. But, as far as I read your
intentions, the answer is "yes", but it would be a different
"uncertainty".

That is, knowing through which
Quote:
slit electrons first pass should produce an accumulation pattern, but if
that pattern were displayed on a wall containing two slits (in this case the
experimenter does NOT determine through which slit the electron passes)
would an interference pattern occur?

The point is that there would be *very few* electrons going through your
second slits in this case. Most of them would be absorbed by the wall,
as there would be large spread of directions.

Quote:

So, in this double-two-slit experiment, determining the first "choice" made
by the pasing electron, but not the second... would there be an accumulation
pattern followed by an interference pattern?

Thanks!

Here I am lost - perhaps you can make your question more precise?

ark.


--

Arkadiusz Jadczyk
http://quantumfuture.net/quantum_future/jadpub.htm
--
Back to top
Andreas Most
science forum addict


Joined: 17 Sep 2005
Posts: 54

PostPosted: Mon Jun 26, 2006 10:47 pm    Post subject: Re: Two-slit experiment Reply with quote

Alf P. Steinbach wrote:
Quote:
[...]
But are there experiments of good standing that directly rule out any
memory of past events in the detector, e.g. with hours between single
events, thermal randomization between events, or the like?

I remember having read about a double-slit experiment where the whole setup
was disassembled and then (after some days) reassembled between the single
events. It was even set up at different places.
After a year (or so) they could clearly see the interference pattern.
I cannot think of any memory effect in such a setup.

Unfortunately, I don't know the reference. Could have been some Japanese
people. Has anybody a clue of where to find this reference?

Andreas.
Back to top
scerir
science forum beginner


Joined: 31 May 2005
Posts: 21

PostPosted: Tue Jun 27, 2006 8:06 pm    Post subject: Re: Two-slit experiment Reply with quote

Andreas Most
Quote:
I remember having read about a double-slit experiment
where the whole setup was disassembled and then
(after some days) reassembled between the single
events.

This one?
http://leifi.physik.uni-muenchen.de/web_ph12/originalarbeiten/taylor/taylor_e.htm

In 1909 Geoffrey Ingram Taylor conducted an experiment
in which he showed that even the feeblest light source
could lead to interference fringes.

"The longest experiment took 3 months, corresponding
to the intensity of a candle more than a mile away"

It seems that this experiment led to Dirac's famous koan
"each photon then interferes only with itself".
Back to top
nightlight
science forum Guru Wannabe


Joined: 27 May 2005
Posts: 182

PostPosted: Thu Jun 29, 2006 3:57 am    Post subject: Re: Two-slit experiment Reply with quote

bz wrote:
Quote:
Wrong. A single photon will produce a single point response somewhere
on the detector plate. The probability of hitting any one point can be
determined by accumulating data from a series of single photons(or
electrons).

Nop, that is a misconception or mischaracterization of the empirical
facts in photon experiments.

The facts are that the response of an array of photodetectors is
statistically indistingushable from droplets statistics of an array of
dripping faucets. Specifically, the best (the most narrow distribution
of triggers) that you will ever get here is a Poissonian distribution
(as long as QED vacuum is there and its vacuum fluctuations).

There isn't anything 'single-photon-like' about it that can
distinguish it from a thresholded EM field measurements (with
photo-electron current measurements results reduced via AD
conversion by the 'pulse analayzer & discriminator' electronics
to a single bit precision, 0/1 values, based on the detector
thresholds) of a classical field.

Nothing distinctly non-classical or non-local (such as the conjectured
instant collapse of a remote EM field) occurs with photo-detections
in double slit/beam splitter experiments. (Otherwise, you wouldn't
need Bell inequality violations tests as the exclusive QM prediction
capable of making such distinction). When a detector placed on
photon path A triggers, the detector at a remote path B will trigger
or not trigger entirely independently (and solely based on its local
field intensities) of what happened with the detector in path A.

In other words, the trigger statistics on A and B detectors is exactly
as if the two wave packet fragments travelled each on its own to
its detector, then triggered it or not based solely on the total
incident EM energy on a photo-cathode within the sampling
window (the 'incident field' consists of the 'signal' EM field
superposed to the ZPF or vacuum fluctuations at the cathode).

For example if you take the array of pair results (A,B) which
are (0,0), (0,1), (1,0) and (1,1) and split it into two sub-arrays
based on results on A, hence as (1,x) and (0,y) sub-arrays, you
won't find statistically smaller proportion of 1's among x values
measured on B (the so-called collapse on B when A triggers)
than among the y values measured on B.

Of course, as with dripping faucets, you can make the detectors
virtually never produce double trigger in a given sequence of sampling
time windows, but you can do exactly the same with the faucets in the
exactlly same way -- either shrink the sampling windows enough or
reduce the input intensity/water pressure enough. In both cases if you
reduce double triggers to single triggers ratio by a factor f, you will
reduce the single trigger to no-trigger ratios by at least the same
factor f, i.e. a setup that virtually never has a double trigger among
triggers, virtually never has a single trigger among non-triggers,
either. It is a trivially unsurprising phenomenon of Poissonian
distribution in the limit p -> 0.

There were a various experments (since 1950s) trying to establish
"single photon" phenomenon i.e. the trigger statistics which would be
distinguishable from that of the array of dripping faucets. It just
doesn't happen. You can read on the very latest one such experiment
claiming demonstration of "single photons" and its detalied analysis
(showing exctly how it cheats) here:

PhysicsForum thread: Photon "Wave Collapse" Experiment...
http://www.physicsforums.com/showthread.php?t=71297

The experiment paper:

1. J.J. Thorn, M.S. Neel, V.W. Donato, G.S. Bergreen,
R.E. Davies, M. Beck "Observing the quantum behavior
of light in an undergraduate laboratory"

Am. J. Phys., Vol. 72, No. 9, 1210-1219 (2004).
http://marcus.whitman.edu/~beckmk/QM/grangier/Thorn_ajp.pdf

The experiment Home Page
http://marcus.whitman.edu/~beckmk/QM/

Quote:
A series of single photons will build up a pattern similar
to that seen when a continuous stream of photons is used.

Again, read or see what actually happens. Nothing statistically
distingushes the photo-detector triggers from drips of an array
of faucets (e.g. you can have interference of the water waves
above the faucets and its effects on the drop counts below).

That conjectured phenomenon (demonstration of a "single photon"
via "sub-Poissonian distribution) has been a holy grail of the
marble-photon branch of Quantum Optics since 1950s when
Hanbury Brown and Twiss experiment showed that it's not how
the EM field behaves, be it in experiments or theoretically
(clasically or in QED).

Such demonstration, experimental or theoretical (within QED
formalism), has yet to be done. You can see for yourself how
miserably the 2004 experiment, the pinnacle of nearly five
decades of pursuit, performed and marvel at the ingenuity,
the means and the lengths at which the authors went to
create the appearance that it finally worked.

If you do know of some experiments or a QED derivation (but
not some handwaved elementary/popular QM stories) that can
distinguish double slit/beam splitter photo-detection trigger
statistics from the trivial classical phenomena such as dripping
faucets in the Poissonian limit p->0, you are welcome to cite it.
Back to top
Oz
science forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 155

PostPosted: Thu Jun 29, 2006 3:57 am    Post subject: Re: Two-slit experiment Reply with quote

scerir <scerir@libero.it> writes

Quote:
It seems that this experiment led to Dirac's famous koan
"each photon then interferes only with itself".

Except we know this is not correct. Experiments have been done where two
separate lasers fired through two separate slits produces an
interference pattern.

Furthermore this happened even if "the probability of two photons being
in the apparatus at one time approached zero".

In any case anyone who has listened to MW radio knows that separate
radio transmitters on the same frequency can readily cause interference
patterns.

--
Oz
This post is worth absolutely nothing and is probably fallacious.
Back to top
Timo Nieminen
science forum Guru Wannabe


Joined: 12 May 2005
Posts: 244

PostPosted: Fri Jun 30, 2006 12:20 am    Post subject: Re: Two-slit experiment Reply with quote

On Thu, 29 Jun 2006, Oz wrote:

Quote:
scerir <scerir@libero.it> writes

It seems that this experiment led to Dirac's famous koan
"each photon then interferes only with itself".

Except we know this is not correct. Experiments have been done where two
separate lasers fired through two separate slits produces an
interference pattern.

That just shows that each photon comes from both sources. A photon is the
quantum of excitation of the EM field, the EM field is the sum of the
fields individually produced by the sources, so each photon comes from
both sources.

It is an excellent demonstration that photons aren't like classical
billiard balls.

--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html
Back to top
scerir
science forum beginner


Joined: 31 May 2005
Posts: 21

PostPosted: Fri Jun 30, 2006 12:20 am    Post subject: Re: Two-slit experiment Reply with quote

Quote:
It seems that this [Taylor's] experiment led
to Dirac's famous koan "Each photon then
interferes only with itself."

Oz writes:
Quote:
Except we know this is not correct.
Experiments have been done where two
separate lasers fired through
two separate slits produces an
interference pattern.

Yes, but this does not mean that Dirac's
koan is wrong.
Even a photon emitted by two sources (in such
a way that you cannot say which of the two sources
emitted the photon) interferes only with itself.
When the different possible photon paths,
from sources to detector, are indistinguishable,
then we have to add the corresponding amplitudes
before squaring to obtain the probability.
The second part of the koan (see below)
seems obscure (or it needs a reformulation),
since we have two-photon interference, that
is to say the interference of photons
emerging from _independent_ sources.

s.

"Each photon then interferes only with itself.
Interference between two different photons
can never occur."
- P.A.M. Dirac, Principles of Quantum Mechanics,
Clarendon, Oxford, 1930, p.15.
Back to top
Oh No
science forum addict


Joined: 06 Apr 2006
Posts: 82

PostPosted: Fri Jun 30, 2006 12:20 am    Post subject: Re: Two-slit experiment Reply with quote

Thus spake Oz <Oz@farmeroz.port995.com>
Quote:
Igor Khavkine <igor.kh@gmail.com> writes
The first link describes a double slit experiment using a very low
emission electron gun. The second one shows a movie of how the
interference pattern is actually accumulated. The interference pattern
appears even when the electron gun essentially fires a single eletron
at a time.

These are all very important experiments.

1) The self-interference of both photons and electrons (and much larger
things like fullerenes). These have all been demonstrated.

2) There is also the interference of two sources each going through one
slit **when intensity is so low that the probability of finding two
'photons' in the apparatus at the same time is very low.

Now this has been demonstrated for photons. However the laser light used
for each beam (separate lasers) had extremely long coherence lengths
(times). To do this with electrons might be problematic (ie
"challenging") but would be interesting. Anybody any ideas how it could
be done?

It can't be done. You probably don't remember or didn't follow it, but

you induced me to calculate interference effects between wave functions
for different photons using qed. The same argument did not apply to
electrons, which are fermions and which are conserved in interaction.




Regards

--
Charles Francis
substitute charles for NotI to email
Back to top
bz
science forum Guru


Joined: 24 Mar 2005
Posts: 833

PostPosted: Fri Jun 30, 2006 12:20 am    Post subject: Re: Two-slit experiment Reply with quote

Oz <Oz@farmeroz.port995.com> wrote in
news:T1db1MScyioEFwLk@farmeroz.port995.com:

Quote:
scerir <scerir@libero.it> writes

It seems that this experiment led to Dirac's famous koan
"each photon then interferes only with itself".

Except we know this is not correct. Experiments have been done where two
separate lasers fired through two separate slits produces an
interference pattern.

Furthermore this happened even if "the probability of two photons being
in the apparatus at one time approached zero".

In any case anyone who has listened to MW radio knows that separate
radio transmitters on the same frequency can readily cause interference
patterns.


What is usually heard there is the 'beat frequency' [hetrodyne] as signals
of two slighly different frequencies (or phases) are 'combined' in the
receiver's detector.

A signal arriving over multipaths can interfer with itself as the phase of
the multipath signals varies due to changes in path length as ionospheric
conditions vary.

Of course a HUGE number of photon is involved as MW radio frequency photons
each carry very little energy.
Back to top
Google

Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 1 of 3 [38 Posts] Goto page:  1, 2, 3 Next
View previous topic :: View next topic
The time now is Fri Oct 20, 2017 5:59 pm | All times are GMT
Forum index » Science and Technology » Physics » Research
Jump to:  

Similar Topics
Topic Author Forum Replies Last Post
No new posts Prine Number thought experiment robert.w.adams@verizon.ne Math 1 Fri Jul 14, 2006 3:31 am
No new posts A Tale of Two Clocks: A Thought Experiment Titus Piezas III Relativity 7 Wed Jul 05, 2006 8:48 am
No new posts Help with atmospheric water vapor partial pressure experi... Dan Akers Chem 3 Thu Jun 22, 2006 11:40 pm
No new posts Liquid Nitrogen in a Swimming Pool - - - Experiment (2006) fufko@sbcglobal.net Chem 11 Sun Jun 18, 2006 2:37 am
No new posts Help please! Need to concoct iron rich gel for a MRI expe... gilak Chem 4 Thu Jun 15, 2006 9:36 am

Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Electronics forum |  Medicine forum |  Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums  |  send newsletters
 


Powered by phpBB © 2001, 2005 phpBB Group
[ Time: 0.0895s ][ Queries: 16 (0.0533s) ][ GZIP on - Debug on ]