My understanding about a photon is this:-
If you set up a few detectors at different distances from a photon emitting source and not one behind the other but randomly arranged and emit a single photon (and the apparatus to do this exists and is used in modern dual slit experiments) it behaves as a wave until it interacts with a detector at which point the wave collapses and cannot be detected by any other detectors further away from the triggered detector. You can also disable detectors so they don’t interact with the photon, but only with those that are enabled.
If you set up a few detectors at different distances from a photon emitting source and not one behind the other but randomly arranged and emit a single photon (and the apparatus to do this exists and is used in modern dual slit experiments) it behaves as a wave until it interacts with a detector at which point the wave collapses and cannot be detected by any other detectors further away from the triggered detector. You can also disable detectors so they don’t interact with the photon, but only with those that are enabled.
^ that would be because the "act of detecting" the photon requires a transfer of energy and thus the photon no longer exists... huh?
If you set up a few detectors at different distances from a photon emitting source and not one behind the other but randomly arranged and emit a single photon ... it behaves as a wave until it interacts with a detector at which point the wave collapses and cannot be detected by any other detectors further away from the triggered detector.
According to QED, rather than taking a single path from A to B, a photon takes every possible path connecting these points, and it takes them all simultaneously.
Detect any one of those possible paths and the wave function of the photon collapses.
The collapse of the wave function is the transformation from a superposition of different probabilities into a 100% probability, i.e., into a localised particle.
Yes detectors but this shows that even in QM the waves are real.If you set up a few detectors at different distances from a photon emitting source and not one behind the other but randomly arranged and emit a single photon
A detected photon via some "electric" detector is rather different.
There is a wiki entry on the emitters that has this comment
The Heisenberg uncertainty principle dictates that a state with an exact number of photons of a single frequency cannot be created. However, Fock states (or number states) can be studied for a system where the electric field amplitude is distributed over a narrow bandwidth. In this context, a single-photon source gives rise to an effectively one-photon number state.
😉 good luck following that up.
https://en.wikipedia.org/wiki/Single-photon_source
Heck, you can do the same thing with electrons, protons, even bowling bowls 🎳 assuming you can make the slits big enough. The line between classical physics and quantum mechanics is disappearing fast.
@gpauk You are probably of the age when a sodium lamp was used as the monochromatic light source and you had to peer at a dim, squashed up interference pattern on a small paper screen.
The demonstration became much more dramatic when lasers became available to school physics departments. The bright red maxima a laser produced could be separated to the extent that the interference pattern spread across the entire wall of the lab!
The demonstration became much more dramatic when lasers became available to school physics departments. The bright red maxima a laser produced could be separated to the extent that the interference pattern spread across the entire wall of the lab!
well, true... I was lucky - I was at school in a short era of very high quality science and maths teaching.. We were very well equipped.
Photon detected : Does that imply the photon is destroyed ?
In other words, do we deal with destructive tests only ? I think so; Non destructive test inducing photon wave collapse would be too much on m'y mind!
Anyway, there is no way to understand QM.
In other words, do we deal with destructive tests only ? I think so; Non destructive test inducing photon wave collapse would be too much on m'y mind!
Anyway, there is no way to understand QM.
I am not surprised that you made no attempt to summarise the content of your link! 😉
Path integral?
We can think of the path integral as stating that a quantum particle samples 'all possible paths'.
Path integrals were invented by Feynman as an alternative formulation of quantum mechanics.
The point I'm making is that the wave collapses when it interaction with an electron. But, the wave is not a point particle - it appears it has volume and it's the whole volume that collapses just like popping a bubble. This can be demonstrated by having randomly located detectors. Turn the closest one on and none of the others get anything. Turn the closest one off, and one of the further away ones on and it detects photons.^ that would be because the "act of detecting" the photon requires a transfer of energy and thus the photon no longer exists... huh?
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I wonder if the path integral was just a mathematical way to describe something that cannot be understood. In other words, to use Feynman's own characterization of another of his pieces of work, renormalization, it's 'mathematical hocus pocus'
As I understand it, the photon's energy is transferred to an electron, which absorbs the energy and it then transits to a higher energy band around the atom it is associated with. It then drops back to its original energy band and in doing so emits a photon, but at a lower frequency.Photon detected : Does that imply the photon is destroyed ?
In other words, do we deal with destructive tests only ? I think so; Non destructive test inducing photon wave collapse would be too much on m'y mind!
Anyway, there is no way to understand QM.
Photon detected : Does that imply the photon is destroyed ? In other words, do we deal with destructive tests only ?
Detecting a photon usually means 'destroying' it in the sense outlined by Bonsai above.
However, in 2013, physicists devised a way to detect single photons of visible light without ending their existence.
The technique observes the 'envelope' containing the information of the photon while leaving the quantum information inside intact.
That way, the photon can 'fly by' after its detection.
The experimental technique is outlined here: https://www.nature.com/articles/nature.2013.14179
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Path Integral formulation is, of course, very Feynman. Very QED.
https://en.wikipedia.org/wiki/Path_integral_formulation#Feynman's_interpretation
One of several mainstream approaches. Principle of Constant Action. Planck's Constant of Action is units Energy x Time too, so its reasonable IMO.
But I prefer Schrodinger waves, just because they are more my sort of familiar study.
https://phys.libretexts.org/Bookshelves/Modern_Physics/Book:_Spiral_Modern_Physics_(D'Alessandris)/6:_The_Schrodinger_Equation/6.2:_Solving_the_1D_Infinite_Square_Well
I have a Lisa Randall book on the go about dark matter.
She's pretty good. And quite wild on speculation!
https://www.thegreatminds.com/speaker/lisa-randall
Just for you, Bonsai, this looks a decent telescope for Christmas!
https://www.jessops.com/p/celestron/ps1000-newtonian-reflector-telescope-97399
Looks alright. Cold business, Astronomy. Ideally you have a South facing window to stay indoors. 🙂
https://en.wikipedia.org/wiki/Path_integral_formulation#Feynman's_interpretation
One of several mainstream approaches. Principle of Constant Action. Planck's Constant of Action is units Energy x Time too, so its reasonable IMO.
But I prefer Schrodinger waves, just because they are more my sort of familiar study.
https://phys.libretexts.org/Bookshelves/Modern_Physics/Book:_Spiral_Modern_Physics_(D'Alessandris)/6:_The_Schrodinger_Equation/6.2:_Solving_the_1D_Infinite_Square_Well
I have a Lisa Randall book on the go about dark matter.
She's pretty good. And quite wild on speculation!
https://www.thegreatminds.com/speaker/lisa-randall
Just for you, Bonsai, this looks a decent telescope for Christmas!
https://www.jessops.com/p/celestron/ps1000-newtonian-reflector-telescope-97399
Looks alright. Cold business, Astronomy. Ideally you have a South facing window to stay indoors. 🙂
Heck, you can do the same thing with electrons, protons, even bowling bowls 🎳 assuming you can make the slits big enough.
To produce significant diffraction, the width of the slits must be of the order of the wavelength being used.
A 7 kg bowling ball traveling at 5 m/s would have a wavelength of around 1.9 x 10^-26 nanometres.
https://www.vcalc.com/wiki/KurtHeckman/DeBroglie+wavelength+(relativistic)
In our everyday life we are protected from such 'quantum weirdness' by the smallness of Planck's constant.
Yeah- I was hoping for you to google something up and post it here ;-DI am not surprised that you made no attempt to summarise the content of your link! 😉
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