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TOPIC: Rodin's Photon Challange

Rodin's Photon Challange 31 Mar 2015 17:17 #21

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rodin wrote:
Blue_Tackler wrote:
Your only valid attempt to 'take it apart' was what you posted on #11 re-two lasers, and that attempt was dislodged by me on #16, and pictured displayed on #17.

Everything else you have typed has nothing to do with the experiment except when you make outakes out of context, looking for a word out of place to clutch at, you can't really find anything wrong with the experiment, you have failed to 'take it apart'.

The point is there is not wave behaviour within the experiment thus the assumption is a photon reality, even the post you quoted to debunk the Aspect experiment stated that only the two lasers would need to be calibrated for the experiment to be good, well the undergraduates have done even better, they have only used one laser.

So in the opinion of your debunking source the experiment is now good. :D

I get that one laser bit BT, we have moved on. I am pointing out that so called photon detector used in the experiment is nothing of the sort.

edit

a similar split beam was used in the old MMX experiment, nothing novel there....

I see, so now that you have failed in your first attempt, you now pick yourself up to try again?
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Last Edit: 31 Mar 2015 17:17 by Frothy.
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Rodin's Photon Challange 31 Mar 2015 17:35 #22

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So are you stating that the single photon counting modules are fakes?

What you miss here sonny boy is that even if they are fake (I don't agree that they are) they still don't signal a wave motion, so even if they don't detect photons ( I think that they do) they are not cohering a wave, thus they are detecting not a wave, a wave would make the same count on all three detectors, this is the main point, the split wave would still be a wave, only particles would arrive at the detectors an inconsistent manner.

Remember the premise of the experiment.
While the classical, wavelike behavior of light ~interference and diffraction! has been easily
observed in undergraduate laboratories for many years, explicit observation of the quantum nature
of light ~i.e., photons! is much more difficult. For example, while well-known phenomena such as
the photoelectric effect and Compton scattering strongly suggest the existence of photons, they are
not definitive proof of their existence. Here we present an experiment, suitable for an undergraduate
laboratory, that unequivocally demonstrates the quantum nature of light. Spontaneously
downconverted light is incident on a beamsplitter and the outputs are monitored with single-photon
counting detectors. We observe a near absence of coincidence counts between the two detectors—a
result inconsistent with a classical wave model of light, but consistent with a quantum description
in which individual photons are incident on the beamsplitter. More explicitly, we measured the
degree of second-order coherence between the outputs to be g(2)(0)50.017760.0026, which
violates the classical inequality g(2)(0)>1 by 377http://people.whitman.edu/~beckmk/QM/grangier/Thorn_ajp.pdf

I'll look into the photon counting modules later but for this fact as long as they do not signal a wave then you have not taken the experiment apart, as the debate is about wave/particle and here there is no wave, by disproving a wave by nature the photon proof is there...
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Rodin's Photon Challange 31 Mar 2015 17:46 #23

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The SPCMs use an avalanche photodiode operated in Geiger
mode to detect the light. They output a 30 ns, 4.5 V ~into
50 V! pulse when they detect a photon, with a 50 ns dead
time between pulses. The SPCMs have a specified quantum
efficiency of ;50% at 810 nm, and the model we used had
dark count rates of ;250 cps. With this dark count rate and
our 2.5-ns coincidence window, coincidences due to dark
counts are negligible.
C. Coincidence counting electronics
As described above, we are interested in detecting coincidence
counts between the outputs of different detectors. We
use a coincidence window of 2.5 ns, and coincidences are
determined using a combination of a time-to-amplitude converter
~TAC! and a single-channel analyzer ~SCA!. Three
such coincidence units are used ~one each for GT, GR, and
GTR coincidences!, and their outputs are recorded by a
counting board in our computer. We briefly describe how we
use the TAC/SCA to determine twofold GT coincidences.
(GR coincidences are determined in the same manner!.
Modification of the TAC/SCA configuration to obtain threefold
GTR coincidences also is described.
A TAC operates by receiving two inputs, called START
and STOP, and then outputing a pulse, the amplitude of
which is proportional to the time interval between the rising
edges of the START and STOP signals. The proportionality
between the amplitude and the time interval is controlled by
the gain of the TAC, and we typically use a value of 0.2
V/ns. To measure GT coincidences, the START input comes
from the output of detector G and the STOP input comes
from detector T ~see Fig. 5!. To ensure that the START pulse
precedes the STOP pulse, we insert an extra length of coaxial
cable, corresponding to a delay of ;6 ns, between T and the
STOP input. Thus, if detectors G and T record simultaneous
detections, the delay between START and STOP signals is 6
ns, and the output from the TAC is 1.2 V.
The SCA operates by receiving an input pulse, and then
outputing a pulse ~with an amplitude of 5 V! only if the
amplitude of the input pulse falls within a certain voltage
window. The width of the window is adjustable, as is thelower level of the window. The input to the SCA is the output
from the TAC. Using the values for the TAC output
above, a coincidence window of 2.5 ns centered about 6 ns
corresponds to a voltage range of 0.95–1.45 V, and our SCA
is configured to output a pulse if the amplitude of the input
pulse lies within this range. The only trick to configuring the
TAC/SCA setup is in properly setting the SCA window to
maximize true coincidences and reject false coincidences.
This procedure is described in Appendix B.
In order to measure the threefold GTR coincidences, we
use T as the START input and R as the STOP input, and
configure the TAC/SCA as described above to register TR
coincidences. To ensure that these TR coincidences also are
coincident with a detection at G, we operate the TAC in
‘‘start gate coincidence’’ mode, and feed the G signal to the
START GATE input of the TAC. If an output pulse from G is
not present at the START GATE when the pulse from T
arrives at START, then the timing circuitry in the TAC is
disabled, and no output is produced.
There is one last trick used in setting up this threefold
coincidence unit. The technique for setting the SCA window
described in Appendix B relies on observing coincidences
between the detectors measuring the START and STOP input;
however, we expect an absence of coincidences between
T and R. In order to obtain coincidences between these detectors
so that we can set the window, we switch the fiber
optic cables so that the idler ~gate! beam is fed into the
detector that ordinarily measures the R output. Now, we have
coincident photons entering the two detectors, so that we can
set the window as described in Appendix B. The delays are
all set by the coaxial ~electrical! cables between the detectors
and the coincidence units. Because all of the fiber cableshave the same length, the optical delays are the same, and
switching the fiber cables back after the window is set does
not affect the timing.
We measure a total of six photocounts in each data acquisition
interval: singles counts from each of the three detectors,
NG , NR , and NT , as well as the coincidence counts
NGR , NGT , and NGTR . We use a counting board that plugs
into a PCI slot in our computer, and it simultaneously records
these counts on six different channels. A LABVIEW program
reads the data from the board, computes the second-order
coherence @Eq. ~14!#, and saves the data.

You're not doing very well at taking it apart you know.
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Rodin's Photon Challange 31 Mar 2015 18:00 #24

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OK there are two points here, you agree and understand so far?

1) Are the photon counters so called really measuring photons, or are they measuring detector granule wave radiation saturation points?

2) Would discrepancies in time/amplitude distribution from detector to detector prove that each detector was not getting same radiation?

Correct?
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Rodin's Photon Challange 31 Mar 2015 19:31 #25

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rodin wrote:
OK there are two points here, you agree and understand so far?

1) Are the photon counters so called really measuring photons, or are they measuring detector granule wave radiation saturation points?

2) Would discrepancies in time/amplitude distribution from detector to detector prove that each detector was not getting same radiation?

Correct?

1) That's more or less what the experiment has set out to prove, that they are measuring photons as by random inconsistencies that are expected to occur at the QM level.

2) Possibly, if the experiment was set up poorly, though the experimenters appear to have been very thorough with regards to setting up, testing and calibrating their equipment as to ensure the same radiation is supplied to each photon counter, as shown here.....
IV. EXPERIMENT
We now describe the major components for our updated
version of the experiment of Grangier et al. The layout of
these components is presented in Fig. 4. In brief, a beam of
ultraviolet laser light enters a nonlinear crystal where, via
spontaneous parametric downconversion, some of the light is
converted into IR light in two beams. Light from one of the
IR beams ~the idler! is used as a gating beam and passes
directly from the crystal into a photodetector. Light from the
other beam ~the signal!, which we shall call the experiment
beam, is directed into a 50/50 BS and subsequently observed
by photodetectors placed in both the transmission and reflection
ports of the beamsplitter. A photodetection in the gating
beam is used to signal that the experiment beam has been
prepared in the proper single-photon state, and it is the light
in the experiment beam whose second-order coherence is
measured. Detections from the three detectors G, T, and R
are registered by a series of time-to-amplitude converters and
single-channel analyzers; coincidence statistics are then compiled
and analyzed.
For a more detailed discussion, it is convenient to group
components of the instrument into three categories: ~i! light
source, ~ii! light detection, and ~iii! coincidence-counting
electronics; there also are some diagnostic instruments that
make the experiments easier to perform. A list of major components,
manufacturers, and part numbers is provided in Appendix
C; all of the equipment is commercially available and
relatively affordable; a complete parts list and further information
is available on our website.27
people.whitman.edu/~beckmk/QM/grangier/Thorn_ajp.pdf

It appears that you might agree that the experiment is workable but you query the results by judging the experimenters as being incompetent
with their equipment.

It's like you're hoping to find a mistake in their method because the experiment in itself is sound. :dunno:
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Rodin's Photon Challange 31 Mar 2015 21:19 #26

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Nothing wrong with the experimenters.

Please note point 2) is what you would EXPECT if discrete photons were involved, and because they get this they say it proves photons.

It does not, however.

The detectors are giving a result that MIMICS the expected. Remember, each firing of the detector is not because of a single photon as the manufacturer claims. This is impossible, once again refer to Gray's paper and thread. Why they see this apparent randomness between detectors firing is because the detection process itself is random, detectors need to absorb enough wave energy to fire, and this varies from detection point to detection point.
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Last Edit: 31 Mar 2015 21:20 by rodin.
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Rodin's Photon Challange 01 Apr 2015 10:27 #27

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rodin wrote:
Nothing wrong with the experimenters.

Please note point 2) is what you would EXPECT if discrete photons were involved, and because they get this they say it proves photons.

It does not, however.

The detectors are giving a result that MIMICS the expected. Remember, each firing of the detector is not because of a single photon as the manufacturer claims. This is impossible, once again refer to Gray's paper and thread. Why they see this apparent randomness between detectors firing is because the detection process itself is random, detectors need to absorb enough wave energy to fire, and this varies from detection point to detection point.

Nice try but fail.

The experimenters are expecting to discover if light has a particle granular property IE photons, or is it simply nothing but a wave.

If it were a wave, and no more than a wave, with no photons nor granular properties then the detectors would collect the wave as it approached them an would log the wave presence as a coherent wave pattern.

They know how a wave behaves and that QM particles behave outside of this range, hence that they detected was not what they would EXPECT from a wave but what they would EXPECT from QM particles ie photons.

The experiment is in tact, your position is becoming quite idiotic and your trying to use semantics to 'take it apart' it's obvious for anyone to read.

Edit - the experiment was carefully set up so that the detectors were receiving the same even flow and portion of light, so no partial wave patterns can be misread as false photons.

Edit 2 - What you propose with regards to the detectors is wrong, because if they were fired by wave portions, the waves would be even and fire them simultaneously and with the same input trigger causing a pattern from source as the laser flow was not altered.

No flow, no wave, simples :yup:
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Last Edit: 01 Apr 2015 10:50 by Frothy.
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Rodin's Photon Challange 01 Apr 2015 11:13 #28

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Edit - the experiment was carefully set up so that the detectors were receiving the same even flow and portion of light, so no partial wave patterns can be misread as false photons.

Edit 2 - What you propose with regards to the detectors is wrong, because if they were fired by wave portions, the waves would be even and fire them simultaneously and with the same input trigger causing a pattern from source as the laser flow was not altered.

No flow, no wave, simples :yup:

I will be out all day but can I leave you once again with the facts of the matter.

Because detectors fire as individual grains in the detector get saturated with radiation RANDOMLY, they give the APPEARANCE of being not 100% cohesive. The same principle applies in the "one photon at a time" double slit experiment. Please read and understand all of reason 4) in the OP here....
4) Wave Particle Duality

One thing unique to QM theory is its invention of the wave-particle paradox. It seemed like wave-particle duality was necessary because the evidence was mounting for the baffling behavior of both light and electrons. In particular, the most baffling of these was the low intensity double slit experiment. Look on the net and see that this experiment is still being argued around after nearly a century....

www.scienceforums.com/topic/11645-7-reasons-to-abandon-quantum-mechanics-and-embrace-this-new-theory/

....speak again this evening
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All establishment lies pass through three stages
First, they are accepted as being self evident
Second, they are exposed by diligent research
Third, they are enforced

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Last Edit: 01 Apr 2015 11:16 by rodin.
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Rodin's Photon Challange 01 Apr 2015 11:46 #29

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rodin wrote:
Edit - the experiment was carefully set up so that the detectors were receiving the same even flow and portion of light, so no partial wave patterns can be misread as false photons.

Edit 2 - What you propose with regards to the detectors is wrong, because if they were fired by wave portions, the waves would be even and fire them simultaneously and with the same input trigger causing a pattern from source as the laser flow was not altered.

No flow, no wave, simples :yup:

I will be out all day but can I leave you once again with the facts of the matter.

Because detectors fire as individual grains in the detector get saturated with radiation RANDOMLY, they give the APPEARANCE of being not 100% cohesive. The same principle applies in the "one photon at a time" double slit experiment. Please read and understand all of reason 4) in the OP here....
4) Wave Particle Duality

One thing unique to QM theory is its invention of the wave-particle paradox. It seemed like wave-particle duality was necessary because the evidence was mounting for the baffling behavior of both light and electrons. In particular, the most baffling of these was the low intensity double slit experiment. Look on the net and see that this experiment is still being argued around after nearly a century....

www.scienceforums.com/topic/11645-7-reasons-to-abandon-quantum-mechanics-and-embrace-this-new-theory/

....speak again this evening

I'm not taking information from randoms on science forums, as fact.

The point is, if the detectors are as you say (I don't agree) they would be saturated by the 'wave' simultaneously, there is no difference with the detector settings or their radiation input.

They don't act randomly, they react to input, and the input is the same, the 'saturation' would be the same, no matter how you try and spin the results, if it was the effect of a wave, the reaction to the detectors would be the same.

There is no reason why the detectors would give different results when they are confronted with an even wave pattern, any saturation would be the same in all detectors, as they are the same, their setting is positioned the same, their input radiation is the same.

The fact that what they result is not the same disproves a wave effect and proves what the experimenters would EXPECT to see from random QM events.

Thus the detectors not only capture photons as per their manufacturing properties but also by their behaviour in the experiment of not cohering a wave.

This conversation is now becoming circular, though I don't see the experiment 'taken apart' it's just that you disagree with the results and the detectors, you disagree with the facts.
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Last Edit: 01 Apr 2015 11:50 by Frothy.
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Rodin's Photon Challange 01 Apr 2015 11:59 #30

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Will you read it here then?

One thing unique to QM theory is its invention of the wave-particle paradox. It seemed like wave-particle duality was necessary because the evidence was mounting for the baffling behavior of both light and electrons. In particular, the most baffling of these was the low intensity double slit experiment. Look on the net and see that this experiment is still being argued around after nearly a century.

The double slit output:



Questions:
1) How can the "photon" know about the other slit if it goes through just one?
2) How can the "photon" interfere with itself it if it just goes through one slit?

The first myth that needs to be cleared up is cleared up with the following statement:

One film dot ≠ One photon detection.

Many QM books have pictures of film dots accumulating like the above picture. Well consider this:

For 200 ISO film, minimum blackening is .004 lux-sec, or 0.27 millijoules/cm². See: stjarnhimlen.se/comp/radfaq.html

So take 1% of this minimum blackening illumination, and consider 0.0027 mJ/cm². This illumination is below the threshold of the film. In other words, this illumination is so weak that no dots are formed on the film. Now, one visible photon has an energy of about 5 x 10-19 Joules
If you do the division, you get that about 5 quadrillion photons can strike a cm² of the film without producing a film dot. Think about this for a moment. 5 quadrillions-worth of photon-energy can strike a cm² of the film and not produce a single film-dot. So these pictures, like the one above, in first year QM books are a serious exaggeration.

So what would happen if an extremely low intensity wave were incident on some ISO 200 speed film? Well, film has tiny silver bromide crystals. These crystals must have crystal defects, or they are not light sensitive at all. So a lot of light could hit these crystals with no effect.

But some crystals have defects, some with more defects than others. These are the most light sensitive crystals. These "most sensitive" crystals are randomly distributed across the film. When the incident light wave intensity just reaches the threshold for film-dot production, it is these "most sensitive" crystals that are randomly activated first. This random activation of the "most sensitive" crystals would start to make a pattern like that seen in figure 5.25A from being struck by a low intensity wave.

A low intensity wave incident on film would produce the patterns seen in the above figure because the film is discrete crystals.

No harm done, you say as you consider yourself an advanced physicist? OK, then let's move on to the next best "one-photon-at-a-time" claim, photomultipliers. The double slit can be done with supposedly "one-photon-at-a-time" photomultipliers!

The same myth needs to be cleared with the following statement:

One photomultiplier tick ≠ One photon detection.

The same reasoning applies to this apparatus. Photomultipliers, like any detection device (be it film, digital camera, etc) have a threshold illumination below which no detection takes place. For example, take the photomultiplier tube in the above paper, with, for example, a blocking area of 10 μm². put it 1 meter away from the double slit and set the crossed polarizers so that the illumination is so low that the photomultiplier ticks once per second. Now move that photomultiplier 100 meters away from the double slit, and increase the blocking area proportionately so it is looking down the same solid angle. Theoretically, according to QM, the same number of photons going down the solid angle at one meter will still be going down the solid angle at 100 meters. So the number of ticks supposedly will be the same. Wrong, the intensity at 100 meters is so low that the photomultiplier will not record one tick per second. It will record nothing but noise. Not convinced? Try it yourself.
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Rodin's Photon Challange 01 Apr 2015 13:51 #31

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You've completely missed the point of the experiment that you have failed to 'take apart'.

It's got nothing to do with the double split experiment.

The detectors in the experiment that you have yet to 'take apart' are all set to the same setting, they have the same radiation input.

If one detector behaves in a particular way due to the volume of radiation input, so does the others, this is the point that you appear to miss...

The detectors are the same, the radiation input is the same, everything is the same, the saturation 'would be' the same.... if we were dealing with waves.

Until you accept this the conversation is pointless and the experiment is in tact.
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Rodin's Photon Challange 01 Apr 2015 14:50 #32

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Some light reading for you in the meantime.
Some kinds of photodetectors are so sensitive that they allow the detection of single photons. It is then possible to register single photon absorption events, rather than measuring an optical intensity or power. It is also possible to register coincidences between two or more detectors; this is very important for many experiments in quantum optics.

− Important Properties of Photon Counters


Photon counting detectors have characteristic properties which are somewhat different from those of other photodetectors. The most important ones are the following:
The dark count rate is the average rate of registered counts without any incident light. This determines the minimum count rate at which the signal is dominantly caused by real photons. The false detection events are mostly of thermal origin and can therefore be strongly suppressed by using a cooled type of detector. To some extent, it also helps to reduce the active area.
The maximum count rate is determined by the speed of the detector or the corresponding electronics. This speed can be limited e.g. by a dead time.
The quantum efficiency is the fraction of incident photons which can be registered. Detection with a small quantum efficiency (i.e., missing out many photons) introduces noise which can be very disturbing particularly for the detection at the quantum noise level (see also: shot noise).
The timing jitter as a qualitative term is the uncertainty of the timing of the registered photon events. It is usually quantified with an r.m.s. (root-mean-square) value.
Particularly for photomultipliers, there is also some fixed time delay between photon absorption and the output of an electrical pulse.

− Photodetectors for Photon Counting


The classical way of single photon detection is to use a photomultiplier tube. Particularly with a cooled photocathode, such a device can have a very low dark count rate. The quantum efficiency can reach several tens of percent in the visible spectral region, whereas devices for infrared light achieve quantum efficiencies of at most a few percent.

Avalanche photodiodes (APDs) can be operated in the Geiger mode for photon counting. Here, the applied reverse voltage is slightly above the avalanche breakdown voltage. An electron can then be triggered by a single photon, and must be stopped by lowering the voltage for a short time interval, which determines the dead time. Depending on the wavelength, the quantum efficiency can be well above 50%. The dark count rate can be strongly reduced by cooling the diode, but this can increase the rate of after-pulses caused by trapped electrical carriers. Silicon-based APDs are used between roughly 350 and 1050 nm and can reach dark count rates of only a few hertz. A typical r.m.s. timing jitter is some tens of picoseconds. For longer wavelengths in the near-infrared region, devices based on indium gallium arsenide (InGaAs) and indium phosphide (InP) or germanium (Ge) are used. Their quantum efficiency is lower than that of silicon devices in the visible spectrum, but higher than for IR photomultipliers. Count rates are typically limited to a few megahertz, or more for silicon APDs.

Hybrid photomultipliers (see the article on photomultipliers) are essentially consisting of a vacuum tube with an integrated avalanche diode; they offer the combination of some beneficial features of photomultipliers and avalanche diodes, in particular a high speed, a high pulse height resolution and a compact setup.

For longer wavelengths, sum frequency generation in a nonlinear crystal allows one to upconvert the photons to the visible spectral range, followed by detection with a silicon APD. A less common approach is to use a superconducting single photon detector.

− Applications


Single photon counters are used in various areas of science and technology:
Some fields of quantum optics, in particular quantum information technology (e.g. quantum cryptography), require single photon detection, often with a high quantum efficiency and with a precise timing for coincidence detection.
Methods such as LIDAR (light detection and ranging) and OTDR (optical time domain reflectometry) have to work with very low light levels and can therefore profit from photon counting detectors.
www.rp-photonics.com/photon_counting.html
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Rodin's Photon Challange 01 Apr 2015 15:13 #33

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Ok, now I pity you as your in check mate.

So I'll give you another chance, do you recall that I stated to you on another thread about Toshiba and their claim to use photons as a code for a communications device?
I recall you answering ''I'll ask a higher power, don't wait up'' or something like that...

Well I think it's time to look into this photon/quantum cryptography a little deeper... hmmmm :ponda: Now I don't want to start you off with anything too complicated, you might in such case just cry 'BOLSHEVIKS' so here's your starter for ten.

Using Quantum Cryptology

Quantum cryptography uses photons to transmit a key. Once the key is transmitted, coding and encoding using the normal secret-key method can take place. But how does a photon become a key? How do you attach information to a photon's spin?

This is where binary code comes into play. Each type of a photon's spin represents one piece of information -- usually a 1 or a 0, for binary code. This code uses strings of 1s and 0s to create a coherent message. For example, 11100100110 could correspond with h-e-l-l-o. So a binary code can be assigned to each photon -- for example, a photon that has a vertical spin ( | ) can be assigned a 1. Alice can send her photons through randomly chosen filters and record the polarization of each photon. She will then know what photon polarizations Bob should receive.

When Alice sends Bob her photons using an LED, she'll randomly polarize them through either the X or the + filters, so that each polarized photon has one of four possible states: (|), (--), (/) or ( ) [source: Vittorio]. As Bob receives these photons, he decides whether to measure each with either his + or X filter -- he can't use both filters together. Keep in mind, Bob has no idea what filter to use for each photon, he's guessing for each one. After the entire transmission, Bob and Alice have a non-encrypted discussion about the transmission.

The reason this conversation can be public is because of the way it's carried out. Bob calls Alice and tells her which filter he used for each photon, and she tells him whether it was the correct or incorrect filter to use. Their conversation may sound a little like this:
•Bob: PlusAlice: Correct
•Bob: PlusAlice: Incorrect
•Bob: XAlice: Correct

Since Bob isn't saying what his measurements are -- only the type of filter he used -- a third party listening in on their conversation can't determine what the actual photon sequence is.

Here's an example. Say Alice sent one photon as a ( / ) and Bob says he used a + filter to measure it. Alice will say "incorrect" to Bob. But if Bob says he used an X filter to measure that particular photon, Alice will say "correct." A person listening will only know that that particular photon could be either a ( / ) or a ( ), but not which one definitively. Bob will know that his measurements are correct, because a (--) photon traveling through a + filter will remain polarized as a (--) photon after it passes through the filter.

After their odd conversation, Alice and Bob both throw out the results from Bob's incorrect guesses. This leaves Alice and Bob with identical strings of polarized protons. It my look a little like this: -- / | | | / -- -- | | | -- / | … and so on. To Alice and Bob, this is a meaningless string of photons. But once binary code is applied, the photons become a message. Bob and Alice can agree on binary assignments, say 1 for photons polarized as ( ) and ( -- ) and 0 for photons polarized like ( / ) and ( | ).

This means that their string of photons now looks like this: 11110000011110001010. Which can in turn be translated into English, Spanish, Navajo, prime numbers or anything else the Bob and Alice use as codes for the keys used in their encryption.
science.howstuffworks.com/science-vs-myth/everyday-myths/quantum-cryptology4.htm
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Rodin's Photon Challange 01 Apr 2015 15:41 #34

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Advancing secure communications: A better single-photon emitter for quantum cryptography

ANN ARBOR—In a development that could make the advanced form of secure communications known as quantum cryptography more practical, University of Michigan researchers have demonstrated a simpler, more efficient single-photon emitter that can be made using traditional semiconductor processing techniques.

Single-photon emitters release one particle of light, or photon, at a time, as opposed to devices like lasers that release a stream of them. Single-photon emitters are essential for quantum cryptography, which keeps secrets safe by taking advantage of the so-called observer effect: The very act of an eavesdropper listening in jumbles the message. This is because in the quantum realm, observing a system always changes it.

For quantum cryptography to work, it's necessary to encode the message—which could be a bank password or a piece of military intelligence, for example—just one photon at a time. That way, the sender and the recipient will know whether anyone has tampered with the message.

While the U-M researchers didn't make the first single-photon emitter, they say their new device improves upon the current technology and is much easier to make.

"This thing is very, very simple. It is all based on silicon," said Pallab Bhattacharya, the Charles M. Vest Distinguished University Professor of Electrical Engineering and Computer Science, and the James R. Mellor Professor of Engineering.

Bhattacharya, who leads this project, is a co-author of a paper on the work published in Nature Communications on April 9.

Bhattacharya's emitter is a single nanowire made of gallium nitride with a very small region of indium gallium nitride that behaves as a quantum dot. A quantum dot is a nanostructure that can generate a bit of information. In the binary code of conventional computers, a bit is a 0 or a 1. A quantum bit can be either or both at the same time.

The semiconducting materials the new emitter is made of are commonly used in LEDs and solar cells. The researchers grew the nanowires on a wafer of silicon. Because their technique is silicon-based, the infrastructure to manufacture the emitters on a larger scale already exists. Silicon is the basis of modern electronics.

"This is a big step in that it produces the pathway to realizing a practical electrically injected single-photon emitter," Bhattacharya said.

Key enablers of the new technology are size and compactness.

"By making the diameter of the nanowire very small and by altering the composition over a very small section of it, a quantum dot is realized," Bhattacharya said. "The quantum dot emits single-photons upon electrical excitation."

The U-M emitter is fueled by electricity, rather than light—another aspect that makes it more practical. And each photon it emits possesses the same degree of linear polarization. Polarization refers to the orientation of the electric field of a beam of light. Most other single-photon emitters release light particles with a random polarization.

"So half might have one polarization and the other half might have the other," Bhattacharya said. "So in cryptic message, if you want to code them, you would only be able to use 50 percent of the photons. With our device, you could use almost all of them."

This device operates at cold temperatures, but the researchers are working on one that operates closer to room temperature.

The paper is titled "Electrically-driven polarized single-photon emission from an InGaN quantum dot in a GaN nanowire." The first author is Saniya Deshpande, a graduate student in electrical engineering and computer science. The work is supported by the National Science Foundation. The device was fabricated at the U-M Lurie Nanofabrication Facility.
www.ecnmag.com/news/2013/04/better-single-photon-emitter-quantum-cryptography

Let me know when you've thought up an excuse for this will ya :dunno:
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Rodin's Photon Challange 01 Apr 2015 15:57 #35

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Single Photon 80 Km Quantum Cryptography Communications



Hokkaido University and Mitsubishi Electric Corporation (MEC) have developed a high precision quantum cipher communication device with a single photon source as a quantum cipher system using a BB84 protocol, and have succeeded in a demonstration of the quantum cipher principle at a distance of 80 km, the world’s longest transmission distance to date.



Hokkaido University developed single photon source capable of suppressing the possibility of the simultaneous generation of more than two photons, and MEC developed a high-precision quantum cipher communication device using this single photon source. Hokkaido University and MEC, in collaboration, succeeded an 80 km demonstration.



Hokkaido University and MEC were financially supported by the Japanese governmental programs JST (Japan Science and technology Agency)-CREST (Core Research for evolutional Science and Technology) and NICT (National Institute of Information and Communications Technology), respectively.


A. Major Achievements 1. Development of a single photon source with a low possibility (one in ten thousand) of simultaneous generation of two photons by Hokkaido University and JST. • Shigeki TAKEUCHI, an associate professor at the Research Institute for Electronic Science, Hokkaido University, achieved a high degree of technical precision with his newly developed single photon source based on a non-linear effect. His technology reduces the possibility of two photons being generated to less than one in ten thousand, a figure that could not be realized using extant ultra-weak pulsed laser source technology. • With this new, single-photon source, researchers could communicate without fear of eavesdropping. 2. Scientists developed a quantum cipher communications device with high precision and stability by MEC and NICT 3. Hokkaido University, MEC, JST and NICT scientists developed an accurate and quantitative security evaluation procedure, and demonstrated communications at a distance of 80 km, the furthest to date in the world. • Incorporating single photon source developed by Hokkaido University, and using electrical signal called heralded signal and clock signal with high time precision, they succeeded in quantum cipher communications device with high precision of detecting single photon and good stability. • Scientists have developed a procedure for quantitatively evaluating information leakage by considering the photon generation process used. • Using this evaluation procedure, scientists confirmed secure communications at a distance of 80 km based on equipment that demonstrated an interface employing a single photon. B. Future Research Scope www.atip.org/atip-publications/atip-news/2007/5126-070119an-80-km-single-photon-quantum-cryptography-communications.html

Be as well stop right there professor Shigeki TAKEUCHI, as rodin say's photon's don't exist, they can't be detected thus you waste your time.
:twitch:
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Rodin's Photon Challange 01 Apr 2015 18:26 #36

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Blue_Tackler wrote:
You've completely missed the point of the experiment that you have failed to 'take apart'.

It's got nothing to do with the double split experiment.

The detectors in the experiment that you have yet to 'take apart' are all set to the same setting, they have the same radiation input.

If one detector behaves in a particular way due to the volume of radiation input, so does the others, this is the point that you appear to miss...

The detectors are the same, the radiation input is the same, everything is the same, the saturation 'would be' the same.... if we were dealing with waves.

Until you accept this the conversation is pointless and the experiment is in tact.

No the radiation is only the same at each detector when averaged out over the macro. At low sensitivities (similar to single photon double slit experiment) there would be an expected spread of triggering due to anisotropy of the detectors. Forget what is says on the box, when "calibrating" these detectors the same error is made, one wonders if it really is a mistake....

Your other experiment I am unable to comment on at this time
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Rodin's Photon Challange 01 Apr 2015 20:18 #37

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rodin wrote:
Blue_Tackler wrote:
You've completely missed the point of the experiment that you have failed to 'take apart'.

It's got nothing to do with the double split experiment.

The detectors in the experiment that you have yet to 'take apart' are all set to the same setting, they have the same radiation input.

If one detector behaves in a particular way due to the volume of radiation input, so does the others, this is the point that you appear to miss...

The detectors are the same, the radiation input is the same, everything is the same, the saturation 'would be' the same.... if we were dealing with waves.

Until you accept this the conversation is pointless and the experiment is in tact.

No the radiation is only the same at each detector when averaged out over the macro. At low sensitivities (similar to single photon double slit experiment) there would be an expected spread of triggering due to anisotropy of the detectors. Forget what is says on the box, when "calibrating" these detectors the same error is made, one wonders if it really is a mistake....

Your other experiment I am unable to comment on at this time

No, the experimenters say that they took particular care to ensure as an exact 50/50 split at the BS as possible thus the detectors would be receiving the same input. They're not going to take up such an experiment and correct the Aspect two laser possible error and then not have the same input themselves, it's all explained on the webpage linked, the detectors are receiving the same input but display different results, that's the entire point of the experiment, the experimenters are not going to attempt the experiment under the conditions that you describe, as they themselves would know the experiment under those conditions would be false, that's why they went to so much of an extent to avoid having different inputs to the detectors, it seems that you have not properly read the experiment details.
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Rodin's Photon Challange 01 Apr 2015 21:23 #38

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Blue_Tackler wrote:

No, the experimenters say that they took particular care to ensure as an exact 50/50 split at the BS as possible thus the detectors would be receiving the same input. They're not going to take up such an experiment and correct the Aspect two laser possible error and then not have the same input themselves, it's all explained on the webpage linked, the detectors are receiving the same input but display different results, that's the entire point of the experiment, the experimenters are not going to attempt the experiment under the conditions that you describe, as they themselves would know the experiment under those conditions would be false, that's why they went to so much of an extent to avoid having different inputs to the detectors, it seems that you have not properly read the experiment details.

Bloody hell, am I not explaining very well? I assume the experimenters ARE performing a 50/50 split in the light beam, no argument there. The problem lies with the detectors, which claim to detect a single photon but in fact only detect a single detector grain firing once it has been heated up by absorbing enough radiation. And there is no saying which one will fire first, be it detector R or T
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Rodin's Photon Challange 08 Apr 2015 13:57 #39

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rodin wrote:
Blue_Tackler wrote:

No, the experimenters say that they took particular care to ensure as an exact 50/50 split at the BS as possible thus the detectors would be receiving the same input. They're not going to take up such an experiment and correct the Aspect two laser possible error and then not have the same input themselves, it's all explained on the webpage linked, the detectors are receiving the same input but display different results, that's the entire point of the experiment, the experimenters are not going to attempt the experiment under the conditions that you describe, as they themselves would know the experiment under those conditions would be false, that's why they went to so much of an extent to avoid having different inputs to the detectors, it seems that you have not properly read the experiment details.

Bloody hell, am I not explaining very well? I assume the experimenters ARE performing a 50/50 split in the light beam, no argument there. The problem lies with the detectors, which claim to detect a single photon but in fact only detect a single detector grain firing once it has been heated up by absorbing enough radiation. And there is no saying which one will fire first, be it detector R or T



BLOODY HELL!!

Can't you understand that there is no difference to the input nor the detectors, so one detector would detect first in a 'united pattern form with the others' to display the heat grain firing signals as you say....

But in the experiment the detectors are not firing as per wave behaviour, their input is the same...

Yet they fire randomly which is what would be expected with QM.

IE no wave pattern detected = no wave detected but the detectors are the same, input the same, if they were cohering a wave, a wave pattern would be displayed in the results.

If two upright poles are inserted into a lake, if a stone is then thrown into the lake and causes a wave disturbance to the surface of the lake, the wave ripples hitting the poles, even if it does not hit them both at the same time, would have a coherent pattern, a wave flow, the wave would have a consistent behavoiur against the two poles as long as it exists, that's what is expected from a wave, same thing with the detectors with this experiment, though here there is no wave pattern to cohere. :thumbup:
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Last Edit: 08 Apr 2015 16:39 by Frothy.
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Rodin's Photon Challange 08 Apr 2015 18:04 #40

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Dear boy, there IS a difference between the detectors. Each one has a detecting substrate, and these cannot be made EXACTLY the same. It's a bit like expecting 2 identical snowflakes every time.... Therefore regardless if they get exactly the same radiation they will fire according to nanocrystal defect distribution which is random. At higher intensities this randomness is lost due to massive sampling numbers, but at low intensity you get one grain firing at a time.

Plant a row of carrot seeds at exactly the same depth. Do they all sprout at the same instance?
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