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Can two photons interfere with each other 
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#1
Aug2505, 08:36 PM

P: 195

Can two photons interfere with each other, or is interference strictly limited to a photon (et cetera) "interfering with itself"?



#2
Aug2605, 01:11 AM

P: 211

Sure, for example in the Michelson Interferometer two different photons interfere to make a dark or a light region in the pattern you see.



#3
Aug2605, 02:37 AM

P: 4,006

marlon 


#4
Aug2605, 12:05 PM

P: 685

Can two photons interfere with each other
Hello εllipse,
unlike the previous two posters, I have another opinion. Photons do not interfere with each other. Example: Double slit experiment Here, one can show that a photon so to say "interferes with itself". You can read the Marcella paper, where the interference pattern is explained quantum mechanically as single photon interference (it's a very good paper! ): Thomas Marcella, "Quantum interference with slits", European Journal of Physics 23 (2002), pp. 615621 Try to download it here: http://www.iop.org/EJ/abstract/01430807/23/6/303 @Marlon: Diffraction can be explained by single photon interference, it's not a result of two photons interacting with each other (see example above). @mmwave: In the Michelson interferometer two photons also do not interact. Another example is the Mach Zehnder interferometer, where single photons show "interference". There's a nice paper on it: “Photon Quantum Mechanics and Beam Splitters,” C.H. Holbrow, E.J. Galvez, and M.E. Parks, American Journal of Physics 70, 260265 (2002) You can download it here for free: http://departments.colgate.edu/physi...es/ajpbs02.pdf 


#5
Aug2605, 12:42 PM

P: 4,006

marlon 


#6
Aug2605, 12:46 PM

P: 4,006

To first order, photons do not interact with each other but in higher order perturbationtheory photons DO mutually interact (indirectly though) via a process called hadronization. marlon 


#7
Aug2605, 01:30 PM

P: 685

I think εllipse is asking whether photons interact in such a way that they annihilate each other like electromagnetic or sound waves.
The post by mmwave for example shows that there's this misconception. But let's ask εllipse what exactly he means with his question.  side note for Marlon: Classically, where you have electromagnetic waves, I agree with you Marlon that there might be a difference between the terms "diffraction" and "interference". For the double slit we have: a) Two infinite narrow slits => only interference pattern b) Two finite narrow slits => diffraction (in the classical sense) pattern also occurs, which can be explained by single slit with finite width However, there might be misunderstanding: When I mention interference I am talking about quantum interference where you add probability amplitudes if indistinguishable ways occur. Then one explains the double slit interference pattern not as a combination of diffraction and classical interference but only as a result of quantum interference (adding probability amplitudes like in the Marcella paper). 


#8
Aug2605, 09:36 PM

P: 195

In my physics class, my teacher teacher mentioned a little about the wave properties of light, and I assumed it was similar to how two out of phase sound waves can have destructive interference, but in reading about quantum mechanics I've learned that the wave properties of photons, and everything else, are waves or probablity, and then you have the Feynman interpretation, where one particle takes all paths and "interferes with itself"; is that right? So I was asking if two particles will interfere with each other or if the interference is limitted to one particle interfering with itself. Maybe I don't know enough of what I'm talking about to ask the question right. Let me try asking another way, and hopefully it'll make sense. Can two light waves which are out of phase destructively interfere and produce no light? And is this a different question from asking, "Can two photons which are out of phase destructively interfere and produce no photons?" Why is quantum mechanics so much more difficult for me to get a handle on than relativity? 


#9
Aug2705, 06:14 AM

P: 685

Hello εllipse,
I'd like to know in which grade you are, then we know how far we can go with our explanations. It only becomes a problem when you turn down the laser intensity and you see single photons behind the double slit: http://www.colorado.edu/physics/2000...twoslit2.html http://www.colorado.edu/physics/2000...twoslit3.html It's like the photon says: "Heh, there's another photon, but I don't care. I only interfere with myself and only listen to MY propability amplitude." The quantum effects seem so weird, but that's what makes quantum theory so interesting. And a question to you: Do you know the double slit experiment, and what problem comes up when you see single photon dots on the screen? This experiment really helped me to understand what is meant by "the photon interferes with itself". 


#10
Aug2705, 06:28 AM

P: 685

One more thing:
There's a book by Richard Feynman with the title "QED: The strange theory of light and matter". It's a book for everyone. And in the first chapter Feynman gives an example of the photon interfering with itself (glassplate, reflectivity changes with thickness). The photon's probability amplitude is illustrated as arrow in this book, just check it out. 


#11
Aug2705, 11:26 AM

P: 343

stuff to learn to "get a handle on" quantum theory. I don't have a handle on it yet, being only an intermittent student  just some of the basics. Below are some links to papers and lists of references. http://student.science.nus.edu.sg/~g...terference.pdf http://www.bu.edu/qil/pdf/PRL090296.pdf http://physics.umbc.edu/Research/qua...tions.new.html 


#12
Aug2805, 01:52 AM

P: 195

Ok, thanks.



#13
Aug2805, 01:56 AM

P: 195

I'm sorry if the answer to this was addressed in the links you provided. It is late here, and I need to get some sleep. I will read through the links in the morning, thanks. 


#14
Aug2805, 03:26 AM

P: 450

Before everything I would like to apologize if I write something false because I don't have a university level in physics. But your discussion seems to be a central pattern relatively to my own approach. As I remark, a part of the discussion is turning around a definition of concept: diffraction, interference, ... By side, everything in the experiment seems to indicate a possible self interaction for the photon. This fact is discussed here with the usual binoculars. May I introduce some new remarks: It is wellknown that every light can be considerred as the superposition of two ellipsoidal polarized waves (see Landau and Lifschitz). What I mean with this: every light (photon) has from the very beginning a dual nature; a photon is a dual thing. Can not this intrinsic duality be the deep reason explaining why a photon can act (interfere) with itself?



#15
Aug2805, 05:46 AM

P: 5

fibre optics, anyone?



#16
Aug2805, 12:58 PM

P: 685

But I want to stress that I would never tell somebody that the wavemodel is "wrong", since it makes correct predictions. But then like in the double slit, when you have a weak laser such that you see single photons, you must use quantum mechanics and you have individual photons that interfere with themselves. For example read the abstract here: http://prola.aps.org/abstract/PRL/v74/i24/p4763_1 The physicist Paul Kwiat uses a Michelson interferometer to make "quantum mechanical bomb tests" See also here, figure 6: http://www.lanl.gov/orgs/p/pdfs/pr/pr_97_98/ifm.pdf where a Michelson interferometer is shown. But from what I read from another discussion board and a paper [3], it's not to be understood as an interference of two photons: I typed in google interfere "Two lasers" and found the following websites: http://www.madsci.org/posts/archives...4535.Ph.r.html http://www.lns.cornell.edu/spr/199902/msg0014357.html http://www.physicstoday.org/pt/vol54/iss8/p62.html Some quotes from them: Besides, it's nice that you already understand the problem with the double slit experiment.  References [1] "Interference of Independent Photon Beams", R.L. Pfleegor and L. Mandel, Physical Review Letters, Volume 159, Number 5, 1967 http://prola.aps.org/abstract/PR/v159/i5/p1084_1 [2] "Quantum Theory of Interference of Light from Two Lasers", Jordan and Ghielmetti, Physical Review Letters, Volume 12, Number 22, June 1964 http://prola.aps.org/abstract/PRL/v12/i22/p607_1 [3] "Quantum effects in onephoton and twophoton interference", L. Mandel, Review of Modern Physics, Volume 71, Number 2, 1999 http://prola.aps.org/abstract/RMP/v71/i2/pS274_1 http://student.science.nus.edu.sg/~g...terference.pdf 


#17
Aug2905, 12:12 PM

P: 343

light waves. You can do this experiment at home and see the regions of constructive and destructive interference. Get recent textbooks on the classical and quantum theories of light if you can. I have to do this myself. :) There are lots of online sources for good condition used books that will probably fit your budget. I don't know what to recommend at this time since I'm still looking  maybe some of the science advisers here can let us know what they think are some good ones. 


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