Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Geezer on 24/09/2009 18:57:08
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Many experiments (e.g. Young's experiment) rely on the production of single photons. What methods are used to produce individual photons, and what methods are used to confirm that only single photons are produced? Also, can I do this at home?
Any useful references would be appreciated - Thanks!
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I have a spare neutron accelerator in the basement. Would that help?
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Generally, the intensity of a source of light can be measured in terms of the # of photons/unit time that it emits. You can turn down the intensity of your source enough to get only 1 photon out per unit time if you want.
Of course this is all quantum mechanics, so the best you generally know is that on average, you expect photons to be emitted at that rate. You might have quantum fluctuations that give you 5 photons at once, for example, but they'd be somewhat rare.
You might also be able to entangle two light "blobs" such that if you measured one with a detector and saw a single photon "hit," you'd know the other bit of light had only one photon in it.
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I have a spare neutron accelerator in the basement. Would that help?
That does not surprise me. No doubt you keep it for self-defence. Probably entirely legal in Texas too.
You ought to change your handle to "JohnnyNeutron".
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No. I am more interested in the answer Mr. Petruccelli gave. He didn't say anything about the measurement aspect but given the answer he wrote, I suspect that this is a moot point.
Besides, I don't interrupt scientific discussions with inane remarks.
And, oh, yes. The accelerator is legal. A lot of aliens 'round here - from space, moron, not Mexico.
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... what methods are used to confirm that only single photons are produced?
Eye of newt toad ...
In 1979 Baylor, Lamb and Yau were able to use toads' rods* placed into electrodes to show directly that they respond to single photons.
http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
[* rod cells in retina]
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... what methods are used to confirm that only single photons are produced?
Eye of newt toad ...
In 1979 Baylor, Lamb and Yau were able to use toads' rods* placed into electrodes to show directly that they respond to single photons.
http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
[* rod cells in retina]
I think I'm out of toads this week and the toadmonger in town folded a couple of weeks ago. Another victim of the recession. Now, my neigbour is a pissed AS a newt, but I don't suppose that would work. But wait, he's got a cat!
"Here, kitty kitty! Here, kitty kitty!"
[No cats were actually harmed during the creation of this posting]
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I think cats would do well to keep clear of quantum enthusiasts
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I think you're on to something there Syhprum.
We already have a "Popular Mechanics" magazine. How about "Popular Quantum Mechanics"?
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jpetrocelli is right as far as I know. It is only necessary to reduce the emissions to an arbitrary low level, via something as simple as a very dark filter for example. Such filters behave in a simple linear way so that the filter will (on average) reduce the number of photons by a fixed factor each time. It is easy then to extrapolate the effects of cascading such filters from measurements of lots of photons to very few - so few that you could ensure that the statistical likelyhood of having more than one photon in your experiment at any one time is as low as needed.
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[...]
It is easy then to extrapolate the effects of cascading such filters from measurements of lots of photons to very few - so few that you could ensure that the statistical likelyhood of having more than one photon in your experiment at any one time is as low as needed.
...especially after the discover of the "photon antibunching" effect.
http://en.wikipedia.org/wiki/Photon_antibunching
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...especially after the discover of the "photon antibunching" effect.
http://en.wikipedia.org/wiki/Photon_antibunching
Woe is me! I think I'll stick to Boolean Algebra.
Why do I get the distinct impression that quantum mechanics was invented by a bunch of bookies? [;D] (gaming bookmakers)
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...especially after the discover of the "photon antibunching" effect.
http://en.wikipedia.org/wiki/Photon_antibunching
Woe is me! I think I'll stick to Boolean Algebra.
Why do I get the distinct impression that quantum mechanics was invented by a bunch of bookies? [;D] (gaming bookmakers)
Quantum Mechanics was created by loonies.
Ahhh... the best of us eh?
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Right! I should have said "deranged bookies".
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http://www.teachspin.com/instruments/two_slit/experiments.shtml
And a little more technical explanation.
http://spie.org/etop/2007/etop07expX.pdf
Or this :)
www.ptep-online.com/index_files/2007/PP-09-19.PDF
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http://www.teachspin.com/instruments/two_slit/experiments.shtml
And a little more technical explanation.
http://spie.org/etop/2007/etop07expX.pdf
Or this :)
www.ptep-online.com/index_files/2007/PP-09-19.PDF
Great links! Thanks yor_on. The last one even contains a Truth Table!
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I know, kind of 'meaty' though :)
Digestively seen I mean.