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Measuring single quanta...
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Existential Angst
Jun 9, 2013, 3:31:44 PM6/9/13
to
So ahm watchin Morgan Freeman and his universe/Wormhole stuff, and they are
showing QM experiments where they are feeding/measuring SINGLE QUANTA at a
time.... ie, one photon. Double slit experiments, some tuning-fork
experiment at 0 deg K, some entanglement stuff....
Is it really possible to do meaningful (read: "real") experiments with
single photons??? These Wormhole guys certainly think so, and I would
imagine it took $millions to set these experiments up.
I mean, if we can't meaningfully pinpoint an electron, how can these guys be
sure wtf is going on with a SINGLE photon??
Now, as I think about it, they seem to be able to detect particle collisions
is bubble chambers, and the resulting sub-particles (incl photons, I
presume), so I guess it is possible to at least detect such things.... at
least in bubble chambers.
But it's hard to imagine single photons, even single electrons being
*controlled* in circuits, etc.
Just curious.
--
EA
Salmon Egg
Jun 9, 2013, 4:19:09 PM6/9/13
to
In article <51b4d813$0$20207$607e...@cv.net>,
It is certainly possible to reduce the intensity of light in a two-slit
apparatus to where the probability of having more than one photon in the
apparatus is tiny. For example, in a three-meter device with an average
of one photon per second, the probability of having two simultaneous
photons is of the order of 1E-08 per second. While relatively slow, an
hour should give pretty good evidence of interference.
Photomultipliers in the green can have quantum efficiency of about 20%.
So you miss 80% of the photons going through. big deal. You do have to
cool the photosurface and dynodes to minimize dark current, but liquid
nitrogen is good enough.
--
Sam
Conservatives are against Darwinism but for natural selection.
Liberals are for Darwinism but totally against any selection.
apparatus to where the probability of having more than one photon in the
apparatus is tiny. For example, in a three-meter device with an average
of one photon per second, the probability of having two simultaneous
photons is of the order of 1E-08 per second. While relatively slow, an
hour should give pretty good evidence of interference.
Photomultipliers in the green can have quantum efficiency of about 20%.
So you miss 80% of the photons going through. big deal. You do have to
cool the photosurface and dynodes to minimize dark current, but liquid
nitrogen is good enough.
--
Sam
Conservatives are against Darwinism but for natural selection.
Liberals are for Darwinism but totally against any selection.
benj
Jun 9, 2013, 5:24:00 PM6/9/13
to
On Sun, 09 Jun 2013 13:19:09 -0700, Salmon Egg wrote:
> It is certainly possible to reduce the intensity of light in a two-slit
> apparatus to where the probability of having more than one photon in the
> apparatus is tiny. For example, in a three-meter device with an average
> of one photon per second, the probability of having two simultaneous
> photons is of the order of 1E-08 per second. While relatively slow, an
> hour should give pretty good evidence of interference.
>
> Photomultipliers in the green can have quantum efficiency of about 20%.
> So you miss 80% of the photons going through. big deal. You do have to
> cool the photosurface and dynodes to minimize dark current, but liquid
> nitrogen is good enough.
Salmon egg forgot to mention that what with cheap lasers and
> It is certainly possible to reduce the intensity of light in a two-slit
> apparatus to where the probability of having more than one photon in the
> apparatus is tiny. For example, in a three-meter device with an average
> of one photon per second, the probability of having two simultaneous
> photons is of the order of 1E-08 per second. While relatively slow, an
> hour should give pretty good evidence of interference.
>
> Photomultipliers in the green can have quantum efficiency of about 20%.
> So you miss 80% of the photons going through. big deal. You do have to
> cool the photosurface and dynodes to minimize dark current, but liquid
> nitrogen is good enough.
photomulitplier tubes today, this isn't millions of dollars but funding
at levels high school students can manage. And if you do a step up in
cost you can use night vision gear that let's you collect the diffraction
pattern as an image instead of scanning for it. I'm sure you've seen
night vision pictures that have that "sparkly" look. Those are individual
photons arriving to make an image.
If you are interested in this you should have already read:
https://en.wikipedia.org/wiki/Double-slit_experiment
Which shows the sort of thing you get, although those images are for
electrons rather than photons which solves the efficiency loss problem of
a photoelectric conversion layer.
Absolutely Vertical
Jun 10, 2013, 3:18:08 PM6/10/13
to
google 'single photon detector'
1treePetrifiedForestLane
Jun 10, 2013, 3:18:22 PM6/10/13
to
there are not any massless rocktons per se, and
Huyghen's terminology of "photon" certainly cannot bbe said
to "mean that," since he uses an explicit "wavelets" construction;
those being spherical waves, emanating from every point
that was excited by th e wavefront (starting
with the initial "point source," such as it is.
I would have to guess, though,
that "the unit photon" is the indivisible period
of whatever waveform, assuming that it is "rational" (or
just a "pure sine wave").
Huyghen's terminology of "photon" certainly cannot bbe said
to "mean that," since he uses an explicit "wavelets" construction;
those being spherical waves, emanating from every point
that was excited by th e wavefront (starting
with the initial "point source," such as it is.
I would have to guess, though,
that "the unit photon" is the indivisible period
of whatever waveform, assuming that it is "rational" (or
just a "pure sine wave").
Shmuel Metz
Jun 10, 2013, 11:05:07 AM6/10/13
to
FUP set
In <51b4d813$0$20207$607e...@cv.net>, on 06/09/2013
>I mean, if we can't meaningfully pinpoint an electron,
Who says that we can't? What we can't do is to simultaneously measure
complementary observables to arbitrary precision. But unless you want
to discuss operator algebras, sci.physics is where you should be
asking.
--
Shmuel (Seymour J.) Metz, SysProg and JOAT <http://patriot.net/~shmuel>
Unsolicited bulk E-mail subject to legal action. I reserve the
right to publicly post or ridicule any abusive E-mail. Reply to
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In <51b4d813$0$20207$607e...@cv.net>, on 06/09/2013
at 03:31 PM, "Existential Angst" <fit...@optonline.net> said:
>So ahm watchin Morgan Freeman and his universe/Wormhole stuff, and
>they are showing QM experiments where they are feeding/measuring
>SINGLE QUANTA at a time.... ie, one photon. Double slit
>experiments, some tuning-fork experiment at 0 deg K, some
>entanglement stuff....
>Is it really possible to do meaningful (read: "real") experiments
>with single photons???
Not in sci.math; your question has nothing to do with Mathematics.
>So ahm watchin Morgan Freeman and his universe/Wormhole stuff, and
>they are showing QM experiments where they are feeding/measuring
>SINGLE QUANTA at a time.... ie, one photon. Double slit
>experiments, some tuning-fork experiment at 0 deg K, some
>entanglement stuff....
>Is it really possible to do meaningful (read: "real") experiments
>with single photons???
>I mean, if we can't meaningfully pinpoint an electron,
complementary observables to arbitrary precision. But unless you want
to discuss operator algebras, sci.physics is where you should be
asking.
--
Shmuel (Seymour J.) Metz, SysProg and JOAT <http://patriot.net/~shmuel>
Unsolicited bulk E-mail subject to legal action. I reserve the
right to publicly post or ridicule any abusive E-mail. Reply to
domain Patriot dot net user shmuel+news to contact me. Do not
reply to spam...@library.lspace.org
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