Double slit experiment

http://groups.google.com/groups?q=sci.physics.research,+%22Double+slit+experiment%22&hl=en&sa=G&scoring=d

1 "Nicolaas Vroom" Double slit experiment woensdag 22 mei 2002 22:46
2 "Hans Aschauer" Re: Double slit experiment vrijdag 24 mei 2002 2:07
3 "Garfunkel" Re: Double slit experiment vrijdag 24 mei 2002 6:32
4 "Steve Carlip" Re: Double slit experiment zaterdag 25 mei 2002 0:42
5 "Nicolaas Vroom" Re: Double slit experiment dinsdag 28 mei 2002 23:22
6 "Nicolaas Vroom" Re: Double slit experiment donderdag 30 mei 2002 3:13
7 "Asdpoi" Re: Double slit experiment donderdag 30 mei 2002 7:43
8 "James Logajan" Re: Double slit experiment donderdag 30 mei 2002 7:44
9 "Nicolaas Vroom" Re: Double slit experiment donderdag 30 mei 2002 21:03
10 "Garfunkel" Re: Double slit experiment donderdag 30 mei 2002 21:04
11 "Garfunkel" Re: Double slit experiment zaterdag 1 juni 2002 0:07
12 "Nicolaas Vroom" Re: Double slit experiment woensdag 5 juni 2002 23:01


1 Double slit experiment

Van: "Nicolaas Vroom"
Onderwerp: Double slit experiment
Datum: woensdag 22 mei 2002 22:46

Has the double slit experiment with single electrons ever been performed and has an interference pattern been observed?

Paul Davies at his book "Other Worlds" at page 65 introduces this experiment as follows:
"This time there etc, for suppose that the intensity of the electron beam is gradually turned down until only one electron at a time passes through the apparatus. It is possible to record each individual electron's point of arrival at the screen using a photo graphic plate."

John Gribbin in his book "In Search of Schrodinger's Cat" at page 169 writes:
"The electron experiment hasn't quite been carried out in this way - there are problems making things on a small enough scale - but equivalent experiments have been carried out by scattering beams of electrons from atoms in crystals. I'll stick with the imaginary double-slit experiment etc"

P. Coveney and R Highfield in their book "The Arrow of Time" write at page 123
"What does quantum mechanics predict? Like a bookie it only gives odds even when a single electron is involved."
we are therefore forced to conclude that the electron.. passing through both slits and interfering with itself before collapsing instantaneously to some spot on the srenn in entirely random fashion."

No one gives the information if this experiment has been performed in reality.

If this is true:
Has the double slit experiment with single photons ever been performed and has an interference pattern been observed? (How was it experimentally demonstrated that actual single photons were involved ?)

I have observed experiments with laser light through diffraction gratings. (But never with single photons or electrons)

Nick

[Moderator's note: extra MIME crud deleted; overlong subject header shortened. - jb]


2 Double slit experiment

Van: "Hans Aschauer"
Onderwerp: Re: Double slit experiment
Datum: vrijdag 24 mei 2002 2:07

Nicolaas Vroom wrote::

>

Has the double slit experiment with single electrons ever been performed and has an interference pattern been observed?

[...]

> I have observed experiments with laser light through diffraction gratings. (But never with single photons or electrons)

I am pretty sure it has been perfored with electrons, but I do not remember the reference.

However, it has more recently been performed with larger molecules:

M. Arndt, O. Nairz, J. Voss-Andreae, C. Keller, G. Van der Zouw, A. Zeilinger
"Wave-particle duality of C60 molecules" Nature 401, (1999) 680-682.

Hope that helps,

Hans


3 Double slit experiment

Van: "Garfunkel"
Onderwerp: Re: Double slit experiment
Datum: vrijdag 24 mei 2002 6:32

Electrons are not easy to use because their charge makes them subject to stray E&M fields and makes them interact rather strongly with matter (such as slits).

The double slit experiment has been performed with single neutrons, in many ways (various "things" done to one or both beams/paths). I suggest you examine your local technical library for books dealing with Neutron Interferometry, or examine Physics Abstracts (for instance) in this subject area.


4 Double slit experiment

Van: "Steve Carlip"
Onderwerp: Re: Double slit experiment
Datum: zaterdag 25 mei 2002 0:42

Nicolaas Vroom wrote:

> Has the double slit experiment with single electrons ever been performed and has an interference pattern been observed?

Yes. A. Tonomura et al., ``Demonstration of Single-Electron Buildup of an Interference Pattern,'' Am. J. Phys. 57 (1989) 117. I understand that Hitachi has produced a full-length film based on this experiment.

There's a very nice description, along with some pictures, in the book _And Yet It Moves_, by Mark Silverman (Cambridge University Press, 1993). This book also has fairly detailed descriptions of a variety of interesting quantum experiments. I strongly recommend it.

Steve Carlip


5 Double slit experiment

Van: "Nicolaas Vroom"
Onderwerp: Re: Double slit experiment
Datum: dinsdag 28 mei 2002 23:22

Garfunkel wrote:
>

Electrons are not easy to use because their charge makes them subject to stray E&M fields and makes them interact rather strongly with matter (such as slits).

In this experiment two things are very important. First that the aparatus allows for two distinct states: One slit is open - versus two slits are open.
Accordingly to litterature when one slit is open there is no interference pattern. When two slits are open there is an interference pattern.

(Diffraction of electrons through gold or coper foil shows interference but does not offer those two states)

Secondly that the particles used should go through the apparatus one by one, in order to exclude any interaction between the individual particles (photons, electrons, neutrons)

> The double slit experiment has been performed with single neutrons, in many ways (various "things" done to one or both beams/paths). I suggest you examine your local technical library for books dealing with Neutron Interferometry, or examine Physics Abstracts (for instance) in this subject area.

I did a search with Google with Neutron Interferometry. I found this URL: http://www.quantum.univie.ac.at/research/thesis/gvdzdiss.pdf

Gravitational and Aharonov-Bohm Phases in Neutron Interferometry Dissertation by Gebrand van der Zouw (He is also mentioned in the article mentioned in the posting by Hans Aschauer)

This dissertation gives IMO an excellent overview and the state of the art of Neutron Interferomentry. Very worthwhile reading.
Two experiments are explained, however not IMO with single neutrons. IMO those experiments do not demonstrate that when single neutrons are used (involving only one neutron at a time) in a double slit experiment that there is an interference pattern.

Nick http://users.pandora.be/nicvroom/


6 Double slit experiment

Van: "Nicolaas Vroom"
Aan: "physics_research"
Onderwerp: Re: Double slit experiment
Datum: donderdag 30 mei 2002 3:13

Steve Carlip wrote:
>

Nicolaas Vroom wrote:

> >

Has the double slit experiment with single electrons ever been performed and has an interference pattern been observed?

>

There's a very nice description, along with some pictures, in the book _And Yet It Moves_, by Mark Silverman (Cambridge University Press, 1993). This book also has fairly detailed descriptions of a variety of interesting quantum experiments. I strongly recommend it.

At page 196 of that book the neutron Mach-Zehnder interferometer is discussed. Only one neutron at a time traverses the apparatus.

The MZ interferometer consists of an incident beam, two beamsplitters BS1 and BS2, two mirrors M1 and M2 and a detector D. Each neutron has a 50% chance at BS1 either to go via M1 or via M2 to the the detector D.

Suppose my single neutron generator generates 1000 neutrons/second than if I place two detectors D1 and D2 just after BS1, in both path, than I expect that each of those two detectors will detect (on average) 500 neutrons.

Suppose I remove D2 than I expect detector D will also count 500 neutrons but there will be no interference pattern.

When I remove D2 than Detector D will count 1000 neutrons and there will be an interference pattern.

Apperently each neutron interferes with itself.

My question is has it been tried to place something into both path such that one still counts 1000 neutrons but that there is no interference pattern ?

(The following URL may be gives away the answer at page 51 but I'am not sure http://www.quantum.univie.ac.at/research/thesis/gvdzdiss.pdf )

Nick http://users.pandora.be/nicvroom/


7 Double slit experiment

Van: "Asdpoi"
Onderwerp: Re: Double slit experiment
Datum: donderdag 30 mei 2002 7:43

Some poor uncited soul wrote:

> Has the double slit experiment with single photons ever been performed and has an interference pattern been observed?

I found this web page regarding such an experiment:

old url http://imogen.princeton.edu/user/page/single_photon.html
new url http://ophelia.princeton.edu/~page/single_photon.html

I would be interested in finding out if a "delayed discovery" double-slit experiment has ever been performed. This would be a classic double-slit experiment using photon detectors, in which the detectors (and the information they contain) are destroyed before any observer examines the screen to see if an interference pattern exists.


8 Double slit experiment

Van: "James Logajan"
Onderwerp: Re: Double slit experiment
Datum: donderdag 30 mei 2002 7:44

Nicolaas Vroom wrote:

> Has the double slit experiment with single photons ever been performed and has an interference pattern been observed?
(How was it experimentally demonstrated that actual single photons were involved ?)

You can find some interesting pictures, and a brief description of the experimental setups of single photon experiments at:

old url http://imogen.princeton.edu/user/page/single_photon.html
new url http://ophelia.princeton.edu/~page/single_photon.html
http://www.physics.brown.edu/Studies/Demo/modern/demo/7a5520.htm

Hope this helps.


9 Double slit experiment

Van: "Nicolaas Vroom"
Onderwerp: Re: Double slit experiment
Datum: donderdag 30 mei 2002 21:03

James Logajan wrote:
>

Nicolaas Vroom wrote:

> >

Has the double slit experiment with single photons ever been performed and has an interference pattern been observed? (How was it experimentally demonstrated that actual single photons were involved ?)

>

You can find some interesting pictures, and a brief description of the experimental setups of single photon experiments at:

old url http://imogen.princeton.edu/user/page/single_photon.html
new url http://ophelia.princeton.edu/~page/single_photon.html
http://www.physics.brown.edu/Studies/Demo/modern/demo/7a5520.htm

Hope this helps.

Really excellent. I'am flabbergasted.

The first picture in the experiment performed at Princeton over 1/30 sec shows 3 photons (hits) Is this number a good average for a double slit ?

Maybe some one can answer the following questions ? 1a. If only one slit (left) is used over 1/30 sec what is the average number of counts ? 1b If only one slit (right) is used etc ?

2. If there is no slit (or a very large one) over 1/30 sec what is the average number of counts ?

Nick http://users.pandora.be/nicvroom/


10 Double slit experiment

Van: "Garfunkel"
Onderwerp: Re: Double slit experiment
Datum: donderdag 30 mei 2002 21:04

Nicolaas Vroom wrote in message news:...
> Garfunkel wrote:
> >

Electrons are not easy to use because their charge makes them subject to stray E&M fields and makes them interact rather strongly with matter (such as slits).

>

In this experiment two things are very important. First that the aparatus allows for two distinct states: One slit is open - versus two slits are open.
Accordingly to litterature when one slit is open there is no interference pattern. When two slits are open there is an interference pattern.

(Diffraction of electrons through gold or coper foil shows interference but does not offer those two states)

Secondly that the particles used should go through the apparatus one by one, in order to exclude any interaction between the individual particles (photons, electrons, neutrons)

> >

The double slit experiment has been performed with single neutrons, in many ways (various "things" done to one or both beams/paths). I suggest you examine your local technical library for books dealing with Neutron Interferometry, or examine Physics Abstracts (for instance) in this subject area.

>

I did a search with Google with Neutron Interferometry.
I found this URL: http://www.quantum.univie.ac.at/research/thesis/gvdzdiss.pdf

Gravitational and Aharonov-Bohm Phases in Neutron Interferometry Dissertation by Gebrand van der Zouw (He is also mentioned in the article mentioned in the posting by Hans Aschauer)

This dissertation gives IMO an excellent overview and the state of the art of Neutron Interferomentry. Very worthwhile reading.
Two experiments are explained, however not IMO with single neutrons. IMO those experiments do not demonstrate that when single neutrons are used (involving only one neutron at a time) in a double slit experiment that there is an interference pattern.

Nick http://users.pandora.be/nicvroom/

Nick,

The neutron flux in a typical neutron interferometer is not very high, and the thermal neutron is moving at a rather high velocity (comparable to the speed of sound, as opposed to the speed of light, but still fast compared to an apparatus that is tens of centimeters across). There is only a very, very low probability that two neutrons are present at once (one can remove the interferometer apparatus and replace it with a high efficiency neutron detector in order to obtain an absolute measurement of the neutron flux incident on the interferometer).

By searching for information available on the Internet, you were pretty well guaranteed finding only recent research results. Stuff like "using a piece of cadmium to block one beam" was done rather long ago -- maybe in the 1960's or so. In the 1970's and maybe part of the 1980's people were conducting experiments like "let's put one 'refractive index' material in one beam, and nothing, or a different material, in the other beam" in order to measure the "coherence length" of the neutron beam, i.e., How much can you delay one beam relative to the other, and still get interference?

Professor Sam Werner and Dr. Helmut Kaiser, at the University of Missouri - Columbia, are among the US researchers with considerable work in this field. There are certainly other significant research groups doing such work elsewhere in the world, such as at Institut Laue-Langevin (ILL) in Grenoble, France.


11 Double slit experiment

Van: "Garfunkel"
Onderwerp: Re: Double slit experiment
Datum: zaterdag 1 juni 2002 0:07

Here is a link to a recent book about Neutron Interferometry (from Oxford University Press, by Rauch and Werner).

http://www.oup-usa.org/isbn/0198500270.html


12 Double slit experiment

Van: "Nicolaas Vroom"
Onderwerp: Re: Double slit experiment
Datum: woensdag 5 juni 2002 23:01

Steve Carlip wrote:

> Nicolaas Vroom wrote:

> > Has the double slit experiment with single electrons ever been performed and has an interference pattern been observed?

> There's a very nice description, along with some pictures, in the book _And Yet It Moves_, by Mark Silverman (Cambridge University Press, 1993). This book also has fairly detailed descriptions of a variety of interesting quantum experiments. I strongly recommend it.

Page 9 of that book shows: a schematic diagram of an electron interference experiment with a field-emission (FE) electron microscope.

Page 11 explains: "How could one be sure that effectively only one electron at a time contributed to the interference pattern? By adjustment of the focal length of one of the lenses, the electron current reaching the detector was set to approximately 1000 electrons/second. Thus, one electron followed another at time intervals of about a millisecond."

I agree that that is true on the average but suppose two electrons leave the FE tip simultaneous in the same (right) direction, then IMO those electrons will also reach the fluorescent film simultaneous. (I'am not claiming that this is what actual is happening)

The FE electron microscope consists of the following: FE tip (source), anode 1, anode 2, lens 1, single aperture specimen plane, lens 2, single aperture, lens 3, electron biprism, image plane, lens 4, fluorescent film.

The biprism splits the electron wave and consists of "a fine wire filament at a potential of about 10 V placed between two parallel plates at ground potential"

Each single electron is emitted in a random direction from the FE tip and should have a random position in any plane. Just before the biprism each electron should still have a random position. Just after the biprism this should not be the case. The projector lens (lens 4) does not cause the interference pattern on the fluorescent film.

To test this you should at least close half of the biprism and observe that there is no interference pattern.

Accordingly to the information supplied in this thread there are three different cases where the double-slit experiment has been performed: With photons, with electrons and with neutrons. (With neutron interferometry there are more possiblities)

My question is: is in each case the explanation the same ie the particle interferes with itself?

Suppose I close/block the right "path" and I count the number of hits at the detector. This number = n(L) = n(Left) For VCN interferometer close after 2 grating. Next, suppose I close/block the left "path" and I count the number of hits at the detector. This number = n(R) = n(Right)

In relation to the above in each of those three cases is n(L) = n(R) in average?

Next, I keep both the left "path" and the right "path" open and I count the number of hits at the detector. This number = n(L+R)

In each of those three cases in average: Is n(L+R) = n(L) + n(R) or Is n(l+R) = n(L) = n(R) (approximate the same) or Is n(L+R) = to something else ?

Nick http://users.pandora.be/nicvroom/


Created: 7 June 2002

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