adding time of flight measurements to double slit experiment

I'm talking about the case where you have fringes but the path lengths are different. That would correspond to the light hitting a screen at an off-center location. Put the detector on the screen at one of the bright, off-axis fringes. What is the time histogram?

Experimentally, a split-beam interferometer is easier to set up to make interferance with very different path lengths, where it would be practical to histogram the transit times.

Indistinguishable? The paths can certainly be of different lengths. If they had to be of identical length to get interferance, you'd only ever see one fringe.

John

Well, I went over to the SAO/NASA Astrophysics Data System and rummaged around for articles by him. I gather there was a 1972, just by him, and a 1973 by Burgess, with him. No access to the articles, though I did find one dated 1977 on velocity dispersions where he wasn't the lead. Any chance you know where copies can be found on the web where I don't need to pay a fee for them?

Thanks, Jon

behind the other slit.

constant x frequency.

issue.

electrons bound to those.

Hi,

I agree, the quantization states of matter were incorrectly assumed to apply to light, but there is no evidence that light is inherently quantized, and some simple evidence against it being quantized is the paradoxes that result when you assume it is quantized. What kind of detector are you thinking of, maybe an array of micro antennas?

cheers, Jamie

I think you miss an inportant point. How exactly are you going to measure TOF of a single photon ? If you detect it near the source, then you can never detect it again, since it will be absorbed by the detector. Two measurements on one photon are impossible, according to how I understand QM.

--
Regards,

Adrian Jansen           adrianjansen at internode dot on dot net
Note reply address is invalid, convert address above to machine form.

I don't think there are. You can always use ADS to grab the location and then raid your friendly university or copyright library in person (or JSTOR if you have access or your local public library does).

The only free public access article with some details I know of is :

Afraid it isn't much but it is better than nothing. The rough description is a high gain image tube followed by a standard videcon camera and a sophisticated set of electronics to determine the timing and centroid of every photon generated flash. It was typically put on the back end of high dispersion spectrographs and gained a nickname of "Instant Paper Creation Scheme" - basically everything that came off it was publishable provided you pointed it at something half decent.

A picture of one ex AAT is online at the Australian Museum.

Description isn't very exciting.

Regards, Martin Brown

I think quantum mechanics says you can only measure a photon once because the measurement (electron orbital increment) absorbs the photon. It may be possible to do an emission measurement as well when the photon is created (electron orbital decrement) I think there are some devices that can do this like SQID's or something!

cheers, Jamie

On a sunny day (Sun, 29 May 2011 15:58:49 -0700) it happened Jamie wrote in :

behind the other slit.

constant x frequency.

DETECTION issue.

electrons bound to those.

I was thinking that photo-multipliers work by light knocking out one photon (worth of energy) from the orbit of an atom (hence I used the word 'bound'), then accelerating it in an EM field, and creating more upon impact in secondary emission etc.. but I would think that a 'non-bound' electron would be more willing to move into some direction when it encounters an electromagnetic wave. Creating 'non bound' electrons is not that hard, any old radio tube had some floating around the heated cathode. Would such a setup, when you put it into some sort of cavity, work as your 'antenna' and would all them (now it are many) electrons give more output for the same incoming wave than the initial electron in a PMT? Not saying this is so, just some idea. One could perhaps use a combination of positrons and electrons as a 'swing', say 'dipole' antenna, but I really have not tried, so that is all philosophy, I think these days they have very advanced ways of detecting the presence of an electron. A non-bound one that was moved a bit to the detector by incoming EM radiation?

behind the other slit.

constant x frequency.

DETECTION issue.

electrons bound to those.

(worth of energy) from the orbit

an electron.

Hi,

The pressure exerted by light is already used to push matter, like lasers used to super-cool matter by dampening its vibrations or an antenna etc. Whether you could say a photon is absorbed in these processes is the real question I think. If there is no photon absorbed, yet work is being done by the light, then the light must not be quantized. I don't know if it is ever possible to directly measure whether light is quantized or not.

cheers, Jamie

Thanks. I had to at least ask. I looked, too. I'll have to make the trip, then. Thanks.

Jon

t)

behind the other slit.

ts)

onstant x frequency.

CTION issue.

d electrons bound to those.

I believe that is what Phil said. So sure the QM happens at the detector. Going through the double slit you use Maxwells equations.

Have you looked at how we do this? The detector is a single PMT, we move a small single slit across the face of the pmt to measure the light intensity at that point.

You can turn down the light intensity and see no change in the interference pattern. (well dark counts from the PMT eventually limit things.)

George H.

behind the other slit.

constant x frequency.

DETECTION issue.

electrons bound to those.

Non-demolition measurement - explain using Maxwell.

--
Dirk

http://www.neopax.com/technomage/ - My new book - Magick and Technology

One could pulse a laser and attenuate the output to the point that, say, 0.001 photons on average got through at each pulse. It's easy to measure when the laser fired, so, whenever you detect a photon at the end of the experimental gadget, you'd know when it started. Histogramming arrival times would show path lengths.

A multihit detector could tell when there was a pileup, namely more than one photon got into the system. For the 0.001 photon/shot case, that would happen about 1 shot in a million.

A modelocked laser will make, say, 10 million pulses per second, with each pulse picoseconds wide. You'd probably need a CW laser, HeNe or something, to get light with a long coherence length, suitable for playing with interferance over long path lengths; so that would have to be chopped with some sort of optical modulator to dole out single photons. This sort of experiment is within the range of an "Amateur Scientist" kind of project.

John

On a sunny day (Mon, 30 May 2011 06:41:16 -0700 (PDT)) it happened George Herold wrote in :

Phil looks at it as a math issue. In my view (tm) the math issue has polluted most of physics. That started with Einstein, who would replace logical reasoning of WHY something happens with and abstract mathematical idea of space-time varying. Einstein was pushed by the US at that time (even pushed into a Nobel for 'photon' while many scientists objected), pushed to 'up' the Jewish image a bit. They picked the wrong guy, Einstein probably had his brain damaged when he was working for the patent office and did see too many designs of perpetuum stuff, etc etc, and finally pulled his own on the science community. I am NOT saying the math is not correct, I AM saying that this mindless parroting of a complete idiot has lead to the weirdest dark ages in science that have ever been.

I was thinking this morning, that long time ago when I first started reading 'sci.physics' it was sort of: "shut up and do the math', the guy who said that actually got some reward but he left Usenet for all I know. There is this momentum that status quo (the peers) has (have), and I do not expect to see any changes in my lifetime, except in a global war where things that HAVE to work WILL be used. This is perhaps one of the purposes of war. But if humanity will last past those wars I dunno, in my view (tm) it may well be the mosquitos that will rule earth after us, as we did (do) after the dinos. Mosquitos were found to survive on the outside of the international space station for weeks. Anyways, sure do the math, and it may just give some result that corresponds with current theory. I have read lots of stuff by Feynman, and seen videos of some of his lectures (for example 'photons particles of light' is on the web somewhere). But Feynman was a 'show man' I do not think he really was that good, and carried away by the same Einsteinian BS as all the others, and maybe enhancing it. So keep it simple, keep a 'mechanical' analogy of what happens at all times, and you will outpace all of them

21 century pseudo science, and that includes CERN. My view (tm) is that "If you cannot do it with those small particles on the desktop, then you cannot do it with a machine the size of the universe'. So, anyways, waves, and of course logic then pops up and says 'what waves? (what is it that waves)'. So there must be, at a much finer level then we at present can detect, some substance (todays pseudo science calls it 'virtual particles popping in and out of existence', in the good old days (tm?) it was called 'ether'), some substance, and THAT is EXACTLY where Maxwell's equations came from, he got them from a fluid model (look him up on wikipedia). So here we are, in an ether, space, like a fish in a tank perhaps,

You may know that not so long ago, when sun was though to orbit earth, there was a theory called 'epicycles' that exactly explained the positions of the planets over time. It was VERY complicated, frightenly complicated, and only a small self promoting clan of 'scientists' could do the calculations and understand it. Now here is something we now see again with all that QM. Probabilities, with a 100% one of QM being complete bullshit, IN SPITE of it giving the right answers. Or basically in Einstineinian land any answer you like, if it does not work 'rework' your math (as we see in LIGO looking for gravity waves). Now there is an interferometer max size, and still nothing after M&M (not the candy).

So, LOL, I like to write these things as a wake up call, but I also know the brain dead do not wake up again likely. That is a good thing in one way: Einstein IS dead, and he wont be able to play an other one on the poor kids that perhaps are to come.

Right, of course a light bulb does not put out very coherent light either but waves at many wavelength, and amplitudes. So 'noise' would be more appropriate perhaps.

I have done the double slit several times myself, and you may have noticed my views on those experiments by now.

I guess this generation (of science rapists) and perhaps the next one too, must die before we see the rising sun of common sense again. Or it may take thousands of years, as we have seen after the Greek civilisation, the Roman civilisation, before somebody sees the emperor has no clothes. After the north American civilisation.

The flip side of this is that you can also produce quantum mechanical diffraction patterns by firing electrons, atoms and even quite hefty robust molecules at a suitably sized regular pattern of slits.

These objects are most definitely normally thought of as particles but can be made to show wave properties. To do the experiment the particles are singly ionised and accelerated then filtered to be monoenergetic. The heaviest molecule I am aware of having been made to perform this trick is the buckminsterfullerene C60 m=720.

Regards, Martin Brown

On a sunny day (Mon, 30 May 2011 18:04:18 +0100) it happened Martin Brown wrote in :

This can be mathematically worked out using the De Broglie wavelength of these macro objects, And it is exactly that same De Broglie who by the end of his life proposed that in QM we only work with the probability where we see a maximum of the wave (that a particle is), but he can say it better than me:

This is the English translation of his 1987 paper I recommend reading it, it does get a bit into the math, but he has a refreshing view. And in fact the only one I have seen that I can agree with. It is also nice that he regularly falls back on fluid mechanics... ether.

Of course you can also look at this another way, and say that your double slits are already measuring the differential TOF. The wave/photon passing through one slit has a path difference compared to the other slit. At a bright band on the receiver, the diff is an even number of half wavelengths. At a dark band its an odd number. So the diff between two adjacent bright bands is just the TOF for 1 wavelength. You can work out what this is for whatever wavelength you use. Is this not the measurement you want ?

The 'interesting' thing is that this does give you a way of making two measurements on one photon, which is where classical explanations of QM fall over.

--
Regards,

Adrian Jansen           adrianjansen at internode dot on dot net
Note reply address is invalid, convert address above to machine form.

something happens

It began earlier with Maxwell

--
Dirk

http://www.neopax.com/technomage/ - My new book - Magick and Technology

snipped-for-privacy@netfront.net ---

Yes. What's cool is that one could run a photon through an interferometer with different path lengths, and get an interferance pattern some distance away from the optics, on a simple screen maybe.

In order to get interferance, the photon has to travel both legs of the interferometer. A photodetector placed in a bright fringe on the screen will tell you, through TOF, which path the photon took. That knowledge is acquired *after* the photon clears the interferometer. So the detection event reaches back in time to force the photon into one leg or the other, even after it's exited the paths. So photon behavior isn't even causal.

Now wonder people have a hard time applying human, logical, verbal explanations to photon behavior. There are no logical explanations.

John

something happens

bit.

office

Einstein predicted all sorts of stuff that later turned out to be both true and useful. Mass/energy conversion. Stimulated emission. Various relativistic effects. Many of them he himself considered to be impractical, by they were there in the math. As far as I know, he didn't get anything wrong. And, as far as I know, everything he found in the math has been experimentally verified.

As far as the Jew thing goes, Jews have been wildly disproportionate contributors to science. That may be part cultural, part genetic, but it's real.

'sci.physics'

some reward

expect to see

work WILL be used.

be the mosquitos

station for weeks.

with current theory.

(for example 'photons particles of light' is

carried away by the same

and you will outpace all of them

There is no mechanical analogy that explains photon behavior. Much less a classical theory that predicts actual photon behavior.

John