Delayed Choice Quantum Eraser Experiment

Started by josephpalazzo, May 07, 2014, 11:37:40 AM

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josephpalazzo

Quote from: Berati on May 13, 2014, 01:27:04 PM
I've seen video's of water waves passing through two slits and forming interference patterns. I always thought that this was because the waves are propagating through a medium (water in this case) and that the medium is particles of water. The interference is that of peaks and troughs of the (water) particles affecting each other. Not sure if this is 100% correct from the view of physics.

The problem with photons (it seems to me) is that there appears to be no medium for the waves to be propagating through and this is especially true if there is only one particle at a time being fired through the slits. How could something interfere with itself? as you pointed out.

Indeed, that is a puzzle with light being a wave and at the same time not having a medium like sound waves or water waves to propagate through. The other piece of the puzzle is that it comes as discrete bundles of energy.




Quote

I had a crazy thought while watching Neil DeGrasse Tyson give a talk on relativity and I might as well ask you here. I'm probably not the first to consider this and I'm probably missing something important, but here it goes anyway.

Dr. Tyson made the point that a photon doesn't experience time from it's point of view because it travels at the speed of light. If photons don't experience time, why should it be considered odd that it could interfere with itself if time is not an issue for it?
Is it possible that the photons interfere with their timeless selves when left alone (they are their own medium), but experience time whenever a measurement of their actual position is made, thus preventing them from interfering with themselves?

Sorry if it's a silly question.


The picture is clearer if you think in terms of you sitting on a photon: according to Relativity, you would experience no time. I don't think that we can speak of the photon experiencing or not the effect of time, only metaphorically.

Casparov

Quote from: Berati on May 13, 2014, 01:27:04 PM
Dr. Tyson made the point that a photon doesn't experience time from it's point of view because it travels at the speed of light. If photons don't experience time, why should it be considered odd that it could interfere with itself if time is not an issue for it?
Is it possible that the photons interfere with their timeless selves when left alone (they are their own medium), but experience time whenever a measurement of their actual position is made, thus preventing them from interfering with themselves?

The problem with this of course is that it's not just photons that interfere with themselves. Louis de Broglie suggested that electrons should have wave-like properties as well when unobserved and it was experimentally confirmed in 1927. Electrons do experience time. Anton Zeilinger has performed an equivalent of the double slit experiment with "fullerenes" with are 60-70 carbon atom's large and showed that they "interfere with themselves" as well. More recently there has been an experiment done using 430 atoms large molecules and these too "interfere with themselves." Full blown multi-atom molecules do experience time.

You can even do Monroe-Wineland-type experiments on these multi-atom molecules, electrons, or single atoms, proving that they are in a state of superposition up until you make a measurement.
“The Fanatical Atheists are like slaves who are still feeling the weight of their chains which they have thrown off after hard struggle. They are creatures whoâ€"in their grudge against traditional religion as the "opium of the masses"â€"cannot hear the music of other spheres.” - Albert Einstein

josephpalazzo

Quote from: Casparov on May 13, 2014, 05:08:09 PM
The problem with this of course is that it's not just photons that interfere with themselves. Louis de Broglie suggested that electrons should have wave-like properties as well when unobserved and it was experimentally confirmed in 1927. Electrons do experience time. Anton Zeilinger has performed an equivalent of the double slit experiment with "fullerenes" with are 60-70 carbon atom's large and showed that they "interfere with themselves" as well. More recently there has been an experiment done using 430 atoms large molecules and these too "interfere with themselves." Full blown multi-atom molecules do experience time.

You can even do Monroe-Wineland-type experiments on these multi-atom molecules, electrons, or single atoms, proving that they are in a state of superposition up until you make a measurement.

Casparov, you should refrain from answering physics questions as you are clueless about this subject, and will only confuse others. If you want to discuss philosophy I would ask you to do that in another thread.

Thanks

Berati

Quote from: josephpalazzo on May 13, 2014, 02:19:01 PM
Indeed, that is a puzzle with light being a wave and at the same time not having a medium like sound waves or water waves to propagate through. The other piece of the puzzle is that it comes as discrete bundles of energy.
This is one of the confusing parts.
How can anything just "be" a wave. Isn't it always a wave of "somethings"? Sound, for instance, is a longitudinal wave of air. If I flick a rope, I create a transverse wave down the material that is the rope. But light can just be a wave and not a wave of particles? Would it not be more appropriate to think of light as photons moving as a wave, with the particles location or momentum before being measured described as a probability wave?


QuoteThe picture is clearer if you think in terms of you sitting on a photon: according to Relativity, you would experience no time. I don't think that we can speak of the photon experiencing or not the effect of time, only metaphorically.
It occurred to me after I made the post that a particle would have to be in many places at the same time in order to interfere with itself. It wouldn't matter if it was in many different times.  Although I can't help but think speed of light has something to do with the strange results we see.

I looked around a little and could not find the answer to this question. Is the same effect with the interference patterns appearing and disappearing observable when single particles are fired at speeds much slower than the speed of light?
Carl Sagan
"It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring."

Casparov

Quote from: josephpalazzo on May 13, 2014, 05:28:01 PM
Casparov, you should refrain from answering physics questions as you are clueless about this subject, and will only confuse others. If you want to discuss philosophy I would ask you to do that in another thread.

Thanks

http://www.nature.com/news/2011/050411/full/news.2011.210.html

QuoteOne manifestation of quantum superposition is the interference that can occur between quantum particles passing through two or more narrow slits. In the classical world the particles pass through with their trajectories unchanged, like footballs rolling through a doorway.

But quantum particles can behave like waves, which interfere with one another as they pass through the slits, either enhancing or cancelling each other out to produce a series of bright and dark bands. This interference of quantum particles, first seen for electrons in 1927, is effectively the result of each particle passing through more than one slit: a quantum superposition.

As the experiment is scaled up in size, at some point quantum behaviour (interference) should give way to classical behaviour (no interference). But how big can the particles be before that happens?

In 1999, a team at the University of Vienna demonstrated interference in a many-slit experiment using beams of 60-atom carbon molecules (C60), which are shaped like hollow spheres. Now Markus Arndt, one of the researchers involved in that experiment, and his colleagues in Austria, Germany, the United States and Switzerland have shown much the same effect for considerably larger molecules tailor-made for the purpose â€" up to 6 nanometres (millionths of a millimetre) across and composed of up to 430 atoms. These are bigger than some small protein molecules, such as insulin.

Photons moving at the speed of light have nothing to do with superposition and interference patterns.
“The Fanatical Atheists are like slaves who are still feeling the weight of their chains which they have thrown off after hard struggle. They are creatures whoâ€"in their grudge against traditional religion as the "opium of the masses"â€"cannot hear the music of other spheres.” - Albert Einstein

josephpalazzo

Quote from: Berati on May 13, 2014, 06:10:11 PM
This is one of the confusing parts.
How can anything just "be" a wave. Isn't it always a wave of "somethings"? Sound, for instance, is a longitudinal wave of air. If I flick a rope, I create a transverse wave down the material that is the rope. But light can just be a wave and not a wave of particles? Would it not be more appropriate to think of light as photons moving as a wave, with the particles location or momentum before being measured described as a probability wave?

If you think of photons as made of "something", then is that "something" made of "something else"? Where do you stop? String Theory postulates that everything is made of "strings". One could always ask, what is a string made of? At one point we have to think that we have reached the end of the line. Right now, we have no way of testing String Theory, and there's a growing dissatisfaction with a theory that is untestable, and that it might be a deadend.

As to the wave/particle duality, if String Theory is wrong, then most physicists accept that the wave/particle duality is the end of the line, and we are stuck with that conundrum: something that behaves like a wave in some circumstances, and as a particle in other circumstances.   


QuoteIt occurred to me after I made the post that a particle would have to be in many places at the same time in order to interfere with itself. It wouldn't matter if it was in many different times.  Although I can't help but think speed of light has something to do with the strange results we see.

I looked around a little and could not find the answer to this question. Is the same effect with the interference patterns appearing and disappearing observable when single particles are fired at speeds much slower than the speed of light?

Electrons travel at a much lower speed than light, and they also exhibit wave/particle duality. So we can safely conclude that wave/particle duality does not dependent on speed.

josephpalazzo

Quote from: Casparov on May 13, 2014, 07:18:40 PM
http://www.nature.com/news/2011/050411/full/news.2011.210.html



That article is about testing the threshold between classical physics and quantum physics. This is called the quantum-to-classical transition. They are also looking at quantum decoherence - that's when the system understudied is interacting with the environment and becomes more and more classical. So the idea is to see if there is interference by passing larger and larger objects through 2, 3 and sometimes 4- slit experiments. In that article the team from Austria were able to pass molecules made up of 430 atoms and they still see interference. As you can tell from the article, nothing knew was learned, just old stuff.

Hakurei Reimu

#82
I find it bizarre that Casparov thinks that citing instances where real entities (430 atom molecules) behave like other real entities (individual photons) is somehow an indictment against realism in any form.
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Berati

Quote from: Casparov on May 13, 2014, 07:18:40 PM
http://www.nature.com/news/2011/050411/full/news.2011.210.html

Photons moving at the speed of light have nothing to do with superposition and interference patterns.
I wasn't asking you as I'm not interested in religious proselytizing.
Carl Sagan
"It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring."

Shol'va

Quote from: Hakurei Reimu on May 13, 2014, 07:56:35 PM
I find it bizarre that Casparov thinks that citing instances where real entities (430 atom molecules) behave like other real entities (individual photons) is somehow an indictment against realism in any form.
That is because he hopes it will fly under the radar of the uninitiated, such as myself (but I always check into it, I never accept it just on, you know, faith). Luckily, there are others here that won't fall for it.

Berati

Quote from: josephpalazzo on May 13, 2014, 07:18:56 PM
If you think of photons as made of "something", then is that "something" made of "something else"? Where do you stop? String Theory postulates that everything is made of "strings". One could always ask, what is a string made of? At one point we have to think that we have reached the end of the line. Right now, we have no way of testing String Theory, and there's a growing dissatisfaction with a theory that is untestable, and that it might be a deadend.

As to the wave/particle duality, if String Theory is wrong, then most physicists accept that the wave/particle duality is the end of the line, and we are stuck with that conundrum: something that behaves like a wave in some circumstances, and as a particle in other circumstances.   


Electrons travel at a much lower speed than light, and they also exhibit wave/particle duality. So we can safely conclude that wave/particle duality does not dependent on speed.

Thanks for the replies.
I'm ok with not having final answers to every question and I feel no need to insert an answer just to make myself feel like the center of the universe.



Carl Sagan
"It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring."

josephpalazzo

Quote from: Hakurei Reimu on May 13, 2014, 07:56:35 PM
I find it bizarre that Casparov thinks that citing instances where real entities (430 atom molecules) behave like other real entities (individual photons) is somehow an indictment against realism in any form.

In Casparov language: real = illusion in THE matrix

Casparov

#87
Quote from: josephpalazzo on May 14, 2014, 08:04:15 AM
In Casparov language: real = illusion in THE matrix

Quote from: Hakurei Reimu on May 13, 2014, 07:56:35 PM
I find it bizarre that Casparov thinks that citing instances where real entities (430 atom molecules) behave like other real entities (individual photons) is somehow an indictment against realism in any form.

Quote“... the atoms or elementary particles themselves are not real; they form a world of potentialities or possibilities rather than one of things or facts.” - Werner Heisenberg

Quote"Quantum states are not physical objects: they exist only in our imagination." - Asher Peres

Quote“If we attempt to attribute an objective meaning to the quantum state of a single system, curious paradoxes appear: quantum effects mimic not only instantaneous action at a distance but also, as seen here, influence of future actions on past events, even after these events have been irrevocably recorded.” Asher Peres

Quote"The objective world of nineteenth-century science was, as we know today, an ideal, limiting case, but not the whole reality." - Niels Bohr

Quote“Solipsism may be logically consistent with present Quantum Mechanics, Monism in the sense of Materialism is not.” - Eugene Wigner

Quote"The material world has only been constructed at the price of taking the self, that is, mind, out of it, removing it; mind is not part of it." - Erwin Schrodinger

Quote"Bell's theorem represents a significant advance in understanding the conceptual foundations of quantum mechanics. The theorem shows that essentially all local theories of natural phenomena that are formulated within the framework of realism may be tested using a single experimental arrangement. Moreover, the predictions by those theories must significantly differ from those by quantum mechanics. Experimental results evidently refute the theorem's predictions for these theories and favour those of quantum mechanics. The conclusions are philosophically startling: either one must totally abandon the realistic philosophy of most working scientists, or dramatically revise our concept of space-time." J F Clauser and A Shimony

Quote"Consciousness is much more of the implicate order than is matter . . . Yet at a deeper level they are actually inseparable and interwoven , just as in the computer game the player and the screen are united by participation." - David Bohm

Quote“Hence it is clear that the space of physics is not, in the last analysis, anything given in nature or independent of human thought. It is a function of our conceptual scheme. Space as conceived by Newton proved to be an illusion...” - Max Jammer

Quote“I regard consciousness as fundamental. I regard matter as derivative from consciousness. We cannot get behind consciousness. Everything that we talk about, everything that we regard as existing, postulates consciousness.” - Max Planck

Quote"The very study of the external world led to the scientific conclusion that the content of the consciousness is the ultimate universal reality.” - Eugene Wigner

Quote"We do not belong to this material world that science constructs for us. We are not in it; we are outside. We are only spectators. The reason why we believe that we are in it, that we belong to the picture, is that our bodies are in the picture. Our bodies belong to it. Not only my own body, but those of my friends, also of my dog and cat and horse, and of all the other people and animals. And this is my only means of communicating with them." - Erwin Schrodinger

Quote"As a man who has devoted his whole life to the most clear headed science, to the study of matter, I can tell you as a result of my research about atoms this much: There is no matter as such. All matter originates and exists only by virtue of a force which brings the particle of an atom to vibration and holds this most minute solar system of the atom together. We must assume behind this force the existence of a conscious and intelligent mind. This mind is the matrix of all matter." - Max Planck

Quote"Multiplicity is only apparent, in truth, there is only one mind... Consciousness is never experienced in the plural, only in the singular. Not only has none of us ever experienced more than one consciousness, but there is also no trace of circumstantial evidence of this ever happening anywhere in the world. If I say that there cannot be more than one consciousness in the same mind, this seems a blunt tautology â€" we are quite unable to imagine the contrary..." - Erwin Schrodinger

Quote"In itself, the insight is not new. The earliest records, to my knowledge, date back some 2500 years or more... the recognition ATMAN = BRAHMAN (the personal self equals the omnipresent, all-comprehending eternal self) was in Indian thought considered, far from being blasphemous, to represent the quintessence of deepest insight into the happenings of the world." - Erwin Schrodinger

Quote"It is not possible that this unity of knowledge, feeling and choice which you call your own should have sprung into being from nothingness at a given moment not so long ago; rather this knowledge, feeling, and choice are essentially eternal and unchangeable and numerically one in all men, nay in all sensitive beings. But not in this sense â€" that you are a part, a piece, of an eternal, infinite being, an aspect or modification of it... For we should then have the same baffling question: which part, which aspect are you? what, objectively, differentiates it from the others? No, but, inconceiveable as it seems to ordinary reason, you â€" and all other conscious beings as such â€" are all in all. Hence, this life of yours... is, in a certain sense, the whole..." - Erwin Schrodinger

Quote"So many people today â€" and even professional scientists â€" seem to me like someone who has seen thousands of trees but has never seen a forest. A knowledge of the historic and philosophical background gives that kind of independence from prejudices of his generation from which most scientists are suffering. This independence created by philosophical insight is â€" in my opinion â€" the mark of distinction between a mere artisan or specialist and a real seeker after truth." - Albert Einstein

Quote“A human being is a part of the whole called by us 'universe', a part limited in time and space. He experiences himself, his thoughts and feeling as something separated from the rest, a kind of optical delusion of his consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection for a few persons nearest to us. Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty.” - Albert Einstein

Quote"The history of science shows that the progress of science has constantly been hampered by the tyrannical influence of certain conceptions that finally came to be considered as dogma. For this reason, it is proper to submit periodically to a very searching examination, principles that we have come to assume without any more discussion." - Louis de Broglie

“The Fanatical Atheists are like slaves who are still feeling the weight of their chains which they have thrown off after hard struggle. They are creatures whoâ€"in their grudge against traditional religion as the "opium of the masses"â€"cannot hear the music of other spheres.” - Albert Einstein

josephpalazzo

^^^^

Perfect example of someone who knows little about physics, and goes on quote-mining to prove an ideology. Creationists, Young-Earth-Creationists, Heliocentrists, Conspiracy theorists, and many other fanatics do exactly that.

Hijiri Byakuren

Quote from: Casparov on May 16, 2014, 02:40:42 AM

Ah, the appeal to authority. Classic. You realize that these 10 second sound bytes prove nothing, yes? No? Of course not, you're a moron.
Speak when you have something to say, not when you have to say something.

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