Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: nilak on 07/09/2016 10:27:53
-
Double slit experiment issue
I would like to show you my own opinion about DSE. I might be silly but I suspect data filtering issue.
Let's suppose we have a detector DA for slit A, DB for slit B and a interference detector D0.
If we consider the photon a wave pulse it means it will go either through a slit or through both. If we don't watch detector A and B we will plot all D0 photons (pulses) and some of them will interfere and create the interference pattern. When we open our "eyes" and watch detectors we correlate DA and DB with photons on D0. If we filter pulses on D0 that are not correlated we obviously won't get a diffraction pattern. D0 Somehow detects the recombining wave. DA and DB either don't detect the split wave or they fire at the same time and the result is excluded because om the experiments only d0 with either da and DB coincidences appear.
Waves don't interfere when we don't have the knowledge which slit they went trough. They interfere when they pass through both slits
I suggest placing an BBo crystal before the double slit to confirm every photon fired.
That's all
-
If we don't watch detector A and B .... When we open our "eyes"
Even if you cover up the display of detectors A & B, detectors A & B are still detecting the photons, and will interact with any photons that go through slit A or B.
I expect this will destroy the diffraction pattern
I suggest placing an BBo crystal before the double slit to confirm every photon fired.
Is this Barium Borate (https://en.wikipedia.org/wiki/Barium_borate) crystal configured for parametric down-conversion?
- I assume that for every photon released, you want two photons out?
- But I understand that the efficiency of this process is very low, so you only get the frequency division effect for about 1 in 1012 photons?
See: https://en.wikipedia.org/wiki/Spontaneous_parametric_down-conversion
-
Yes, that is right the crystal need to be configured for SPDC. Indeed the conversion efficiency seems to be very low and unfortunately will probably create technical problems
-
One photon = one interaction, whether that interaction involves detection before or after a slit, the production of more photons, or stimulation of a photographic film.
The interesting point about Taylor's experiment is that photographic film requires at least two visible photons to strike a halide grain in a short time to produce a stable blackening. If the photon flux is too low, the effect of the first photon will dissipate before the second hits the grain ("reciprocity failure").
Now if a single photon really passes through both slits at the same time, what comes out of each slit must have about half the energy of the initial photon. So if we start with 2 eV (green) photons and put a high-pass (green) filter behind the slits, we won't get an interference pattern because all the half-energy (now infrared) photons will be absorbed by the filter. Has anyone tried this? I don't know of an actual published reference.
The small print of Taylor's experiment says "on average, not more than one photon at a time..." So if that is to be believed, and given that photon emission from the sources available to him is always a statistical business, there will have been times when more than one photon was present, which invalidates the principal conclusion.
On the other hand if there really was only one at a time, the astronomers' trick of pre-fogging a photographic plate to increase its sensitivity (taking it out of the reciprocity failure zone) would have allowed the capture of single-photon events and meant that the observed interactions were effectively between existing and pre-existing photons, one at a time.
-
Due to the exremel low conversion efficiency of the BBo my suggested setup, most probably, won't work.
That was for the "Delayed Choice quantum eraser experiment" which uses BBo crystal to obtain the which path information.
However we can use other method to obtain which path, for example, polatization filters.
My prediction about what is going on is that the photon starts traveling as a EM wave of specific energy. Due to the amplitude it spread out and passes through slits and lands on the panel (you can either see them if you have a stream or detect them using a detector if the come one by one). The electrons on the receiver ( panel or detector) will act like quantum mechanical objects and change state. The probability of changing the state is given by the wave that "lands" on the electron. In other words the electron doesn't change state when receiving the exact quantity coresponding to a photon energy of that specific wavelength. It changes energy the level within the atom following a probability function. And when it does that it either emit one photon or it gets detected by the detector. For example if an hidrogen atom is hit by the full wave of a pulse of light, the electron changes level 100% of times. If it get half wave it does it in 50% of the times.
My prediction might be wrong but the key point is that we need somehow to confirm every photon fired.
-
Now if a single photon really passes through both slits at the same time, what comes out of each slit must have about half the energy of the initial photon. So if we start with 2 eV (green) photons and put a high-pass (green) filter behind the slits, we won't get an interference pattern because all the half-energy (now infrared) photons will be absorbed by the filter. Has anyone tried this? I don't know of an actual published reference.
It is generally thought that the photon only pass through one slit but we simply can't detect which one.
So 2ev will result in also 2ev on the other side of the slits.
My prediction based on this experiment is that the wave pulse splits between slits but the wavelength remains constant. The probability tho get detection of the same wavelength on either sides is 50% for each side. This is extremely similar to quantum spin behavior. The probability to get a detention on the screen at a posion x is given by the probability wave between slits.
-
The situation is complicated, or possibly simplified, by the fact that you can do the experiment with massive particles from electrons up to buckyballs (so far) and get exactly the same result, so the detector must be detecting "entire" photons, neutrons, molecules or whatever.
-
macroscopic version of the experiment is shown in quantum walker http://arxiv.org/pdf/0706.3181.pdf
-
macroscopic version of the experiment is shown in quantum walker 3181.pdf
If I'm not wrong, that is not an experiment but a simulation of a quantum walker. Also the algebra it's too complicated to me to be honest. What I understand is that the walker position in never known but the probability of being in a certain position is given by the probability distribution. The probability wave goes through both slits and interfere with itself. But you never know which slit the walker gets through. I have no idea how to simulate the detection process. Simulation of the delayed choice quantum eraser would be epic.
For the photons we can only see quantum behavior during interactions because we can only detect interactions. In the case of the photon the wave is real and the interaction of the wave produces a quantum behavior. That is the difference.
-
you can see the experiment here
youtu.be/fnUBaBdl0Aw
youtu.be/nmC0ygr08tE
-
The experiment with the silicone drop is fascinating. However it shows a particle generating a wave. Then the wave interacts whith obstacles and in the case of the DSE it can pass through both slits and interract with itself on the other side. Only the visible waves interact with the particle. The waves contain some information about the past as well. Now, in this experiment, we always know where the drop is but the wave is always present and interference can occur. Also in order interference to occur the wave must have a certain spread-out to enable enterting through both slits. In an analogy with the EM pulse wave, we should get a light interference when sendind the beam through 2 slits even when we know the which path, if the slits are small enough, for example 1/4 of the original and distance between slits, 1/4 as well.
It is normal that when the wave pases both slits produces interference and when passing through only one producess way less.
In the DSE experiment using light, we never know where the photon is when the interference appears. When it is detected the interference disapears. That is the mistery.
-
Another aspect. All DS experiments point to a weird conclusion. All universe is full of photons that always travel as waves. We are always surrounded by photons that travel like waves an never like particles, ...except for a few insignificant photons that decide to become particles when sometimes few scientists make a DS experiment and find wich way path. They do something that they never did before in the whole universe, travel as a particle. Who cares about them?
-
If we go to the mathematical model, it shows that the probability of the photon of coming through slit A, is the probability generated by the slit A, plus another probability that is independent of which slit it goes through divided by two - 2Re(A(s1)A*(s2)). The explanation is that we always filter this term in these experiments.
-
Although it is of no concern, I also believe a real interference is taking place. Of course the prevailing theory is that there is not a real interference but the convergence of multiple, possible paths at the correct time distance interval to allow photon actualization. However, I admire your train of thought and your desire to verify it through experimentation.
I believe there has already been experiments of this type. Aephram Seinberg at the University of Toronto used low level energy to photograph photons in transit. It was demonstrated that the photons passed through only one or the other of the slits and then proceeded to the double slit nodal position at the final screen. Low energy photography by others also verified that photons can only be detected along a path at the appropriate time distance intervals. Thirty or forty years ago there was a demonstration at a Canaveral Hanger in which high energy particles were sent through a double slit. Some of the particles did not make it to the target screen but ionized atoms in the atmosphere. This provided a very visible tracing of the paths. The results were the same. Any explanation of the double slit experiments must take these results into account.
The path through which slit has always been determinable form very early on. This is because the angle of incidence for each photon corresponds to only one path. Kiem and Lowel used lenses to separate the photons by the angle of incidence and did not disrupt the double slit pattern. The early experiments with slits and the Fresnel mirror achieved the same thing even more dramatically. Why the concept that path determination can destroy an interference pattern has become a sacred cow is a mystery to me. I am sure there will be plenty who will answer it.
Anyway keep on thinking and designing experiments and augment it with as much existing experimental results as possible. There is a growing call for new theory and you may stumble across it.
-
The delayed choice quantum eraser invokes retrocausality.
This phenomenon is also predicted by Wheeler-Feynman absorber theory which basically says a positron is actually an electron going back in time.
It might be that these almost absurd conclusion of these theories to be correct.
A simple example of time travel: imagine an universe made of empty space and two perfect spheres going toward each other. After they colide say they move in opposite directions, the same speed as before. Now either going backwards in time or plotting the future is absolutely the same thing. In this example we don't need retrocausality to explain what happens but in reality some phenomena might be explained by it.
-
Update:
There is a concept of matter and space that I'm currently analizing. If parts of this are correct it implies a certain photon behaviour.
Photons are generated by electrons lowering their energy level. But, from my model it results that electrons always generate 2 twin photons, and the trajectory is determined by restrictions. If you have a laser both twins go the same direction.
To detect a photons, detectors use photoelectric effect. But If the energy emmited by an electron is the energy of 2 photons of the same wavelength, it means to produce one photoelectron you also need 2 photons at the same time (or more, but it is highly improbable).
When one photon goes through one slit and the other twin through the other slit, these photon can't be detected. But after they go through the slits they can interfere and cancel each others energy, or to add up.
The only problem I see here is that the photons should be all in the same phase, otherwise the interference gets random and will apear as continuous band, not stripes. However photon pairs that don't are not in phase arrive at different times and the electron looses it's energy until the other twin arrives. So they must arrive at almost the same time.