Introduction to Delayed Choice Quantum Eraser Experiment
Physicist Thomas Campbell talks in his lecture about the nature of reality and he claims that we are living in a virtual reality. He comes to this conclusion due to quantum physics or to be more precice due to the results of the double slit experiment. This article will explain the setup and the result of this experiment in easily understandable terms and will then point out Tom's reasoning.
The content of this entire article is also available as a video which might even present the key points in more comprehendable terms due to animated graphics :
1. General introduction to the double slit experiment
The basics on the double slit experiment have already been summarized in a different article in the Knowledge Base, thus only the key points will be revisited here :
This experiment originated from the questions whether light is a wave of a particle. When a wave hits a single slit it produces an effect called diffraction. Diffraction means that a new circular wave is being created behind the slit. When we look at two slits next to each other these two newly created waves interact with each other and create to an interferance pattern.
In the double slit experiment photons are being shot at a double slit and behind the double slit the result of the experiment is being monitored on a screen. If a photon - and you could also say if light - behaves like a wave, then the image on the screen should show an interference pattern of the two newly created waves behind the double slit as it is shown in this image. On the other hand if a photon behaves like a particle, we would simply expect two bars on the screen. Each particle would fly either through the left or the right slit and would cause a spot of light on the screen behind that slit. Repeating the experiment many times would lead to two bars formed by all the accumulated individual dots.
In the basic setup of the double slit experiment we always see an interferance pettern on the screen. So photons appearantly are not particles but behave like a wave, because they show diffraction at the slit and thus cause an interferance pattern that can be measured on the screen.
If a photon detector is placed at each slit it becomes possible to identify each individual photon as it flies through ether slit. After modifying the experiment in this way, the image on the screen suddenly shifts from an interference pattern to only two bars, one behind each slit, just as one would expect it if photons were particles.
By performing a measurement at each of the slits, the photons changed their behaviour from that of a wave to that of a particle. Since measuring through which slit each photon traveled is not quite as simple as "placing a photon detector at each slit" the precise setup of the experiment will now be presented in the second chapter of this article.
2. Delayed Choice Quantum Eraser Experiment
This experimental setup shows the "delayed choice quantum eraser" experiment as it was propsed in 1982 by Scully and Drühl. At that time the required measurement equipment was not available thus the experiment was first performed in 1999. Even though the setup looks a little complicated, you will have understood it in a few minutes :
Behind the double slit a beta barium borate crystal is used, which causes the photons from either slit to split into two identical entangled photons with half the frequency of the original photon. Why this splitting is required will become clear in a minute. The yellow lense has the task to redirect photons which have traveled through the first slit and thus are on the red path and photons which traveled through the second slit and thus are on the blueish path so that either one hits sensor D0 at exactly the same location. The intention behind this is being able to measure at sensor D0 whether a bar or a diffraction pattern is being created by the photon without being able to determine through which slit the photon originally traveled. The information about which slit it came from is deliberately erased by only using one sensor which can not distinguish which slit the photon came from.
Lets first take a look at the red path. A photon flies through the first slit and is split into two identical photons at the beta barium borate crystal. The first of the two identical photons flies towards the yellow lense, the second flies downwards and is redirected by two prisms until it finally hits the first green semi-permeable mirror. The 3 green mirrors all have the same attributes, they allow the light to simply pass through 50% of the time, in the other 50% the light is completely reflected and thus redirected. So the decision of which path the photon travels at the green mirrors is a random process with a 50/50 chance. On average every second photon is redircted upwards and hits sensor D4. In the other case the photon is not affected at all and simply travels through the mirror. It then strikes the grey mirror which simply reflects it an it reaches the second green mirror.
Unfortunetely the depiction of this second green mirror is slightly incorrect in the original graphic and it should rather be oriented as indicated here so that the reflection angle matches the setup. In the first case, the photon is not affected by the mirror, simply travels through it and hits sensor D1. In the second case it is reflected and hits sensor D2.
Lets take a look at the blueish path of photons which traveled through the second slit : They are also split into two identical photons and the one travelling downwards is also redirected by the prisms. At the first green mirror every second photon is reflected and hits sensor D3. In the second case, the photon simply travels through the mirror, hits the grey mirror and subsequently this second green mirror, which you should again imagine to be turned by a few degrees. 50% of all photons travel straight through the mirror and hit sensor D2, the other 50% are reflected and hit sensor D1.
Photons which traveled through the first slit and thus are on the red path can only reach sensors D1, D2 or D4, they can never reach sensor D3. Which of the 3 sensors they actually hit is a random process that depends on the green mirrors but they will inevitably reach one of these 3 sensors. The same logic applies to the blueish path. Photons which traveled through the second slit, can only reach sensors D1, D2 or D3 but never sensor D4. Thus it should be clear that a photon that hits sensor D4 inevitably traveled through the first slit, because photons who traveled through the second slit have no way to reach sensor D4. The same logic applies for sensor D3, any photons reaching it must have traveled through the second slit. For photons which end up in sensor D1 or D2 it is not possible to determine through which slit they actually traveled because those two sensor can be reached on the red path from the first slit aswell as on the bluish path from the second slit.
Now you have almost understood the setup of the experiment. One element that is missing is the function of sensor D0 at the top and the reason why the photons travelling through either slit had to be split into two entangled photons by the beta barium borate crystal.
Sensors D1 to D4 are identical sensors, they can only detect that a photon has hit the sensor but are not recording any image. Whereas sensor D0 is similar to a camera and is able to record the exact location where the photon ended up on the screen.
The last aspect that needs to be understood before looking at the results of the experiment is related to the time it takes the photons to travel through the experimental setup. Light travels at the speed of light, thus the shorter the path the earlier the photon reaches the sensor. The experiment is designed in a way so that the path of photon travelling towards the yellow lense always hits sensor D0 first, before its entangled partner reaches the first green mirror. Thus the result of the measurement of sensor D0 is always recorded first and then with a short delay the partner photon hits one of the sensor D1 to D4.
The Coincidence Counter on the right has the task to process the result of the measurement of all 5 sensors. It establishes a connection between the measurement result of sensor D0 with the entangled photon detected by sensors D1 to D4. This way every single photon measured by sensor D0 can be precicely assigned to one of the sensors D1 to D4 where its entangled partner was measured. The measurement data of sensor D0 can thus be split up into 4 individual images, each assigned precisely to one of the sensors D1 to D4.
This picture depicts the raw measurement data of sensor D0 on the upper left. This raw data only shows a wide bar of light in the center of the screen so in this raw state the data is pretty much useless. It is only when each individual spot of light of the raw data is assigned to the sensors D1 to D4 where the entangled partner photon was measured, that a pattern becomes visible :
Two aspects stand out immediately : The data assigned to sensor D1 and D2 shows an interference pattern while the data assigned to sensor D3 and D4 shows no interference pattern.
For photons which reached sensor D1 or D2 it is impossible to determine through which of the two slits they traveled, since the path information has been "erased" by the 50/50 chance events at the green mirrors. Their entangled partner always creates an interference pattern, similar to the double slit experiment without photon detectors at the slits.
For photons which reached sensor D3 or D4 the path of the photon through the first of the second slit can be identified. Their entangled partner does not create an interference pattern, similar to the double slit experiment with photon detectors at each slit.
Why should this result really make us think about the nature of reality ?
The problem with this result is that the photon that travels on the upper path reaches sensor D0 at a time, when its entangled partner photon is not even at the first green mirror. At this moment the photon can not really know whether it should create an interference pattern or not because due to the longer path the result which sensor its entangled partner has traveled to is still undetermined.
How can the upper photon know in advance for every single measurement on which path its entangled partner will be travelling through the green mirrors ? It can not know, because this decision at the green mirrors is a random event with a 50/50 chance.
Nevertheless the results show that obviously the upper photon knew exactly what to do in each case, otherwise the data assigned to sensors D1 or D2 would not form an interference pattern, while the data assigned to sensors D3 or D4 shows no interference pattern. Did you grasp the paradoxical nature of the result of this experiment ? In case you didnt, maybe jump back and rewatch the last few minutes.
What do scientists have to say about the results of this experiment ? When approaching the results of the Delayed Choice Quantum Eraser experiment with Newtonian physics and a purely materialistic worldview there is no way of explaining its results, thus many scientist simply avoid the entire topic because it seems as if causality and time are being violated here.
While the formulas of quantum physics can describe the effect mathematically, it is difficult for any laymen to grasp these rather abstract derivations and conclusions. As an alternative to these sophisticated formulas I would like to present you now in the third chapter of this article with a model of reality physicist Thomas Campbell has come up with because his model can explain these strange results in easy language.
3. Thomas Campbell's modell of a virtual reality
Thomas usually presents his My Big Toe model of reality in a two day workshop in about 16 hours. Since only few people are willing to invest this much time not to mention reading a 800 page book, this will be an attempt to use only selected aspects of his model to explain as good as possible what might be going on here. So be prepared that not everything will be derived from square one and that a few things will simply be assumed which Tom derives in detail in his book. Tom claims that we are living in a virtual reality. What exactly is this guy talking about ? The basic idea will be explained with the help of the following graphic :
The lower part of this graphic represents our 3D physical reality. In it resides everything that we perceive around us. Tom postulates that there is an additional meta layer of information that contains all information about our physical reality but is located outside of our 3D reality. This meta-layer is indicated in the upper part of this graphic. Higher dimensions as a general concept is not really uncommon. Many different scientific models like string theory use this concept so the assumption that there is something beyond our 3D reality construct is not unscientific at all.
In order to better understand this concept we will be taking a look at entangled particles as an example since they have been used in the delayed choice quantum eraser experiment. Due to the process how entangled particles are created, one has a spin-momentum that is up and one has a spin-momentum that is down. You can visualize spin-up as a particle rotating around its own axis clockwise and spin-down as a particle rotating around its own axis counterclockwise.
Due to physical conservation laws the spin of one particle can not change unless the spin of its entangled partner changes at exactly the same time. This changing at exactly the same time even applies if both particles are separated by a distance of several light-years.
In quantum physics this effect was once called spooky action at a distance by Albert Einstein, because this effect has puzzled scientists for decades. It seems as if the information about the spin is transmitted instantaneously between both particles and thus seems to travel faster than the speed of light, which would violate the theory of relativity. How does Tom explain this phenomenon ?
Tom says, that actually the information about both entangled particles is stored in the meta-information layer outside of 3D reality. Our 3D reality is created based on this information, thus the term virtual reality. If the spin of the left particle is being changed, then this information is available instantaneously on the meta-information layer.
With currently available technology we can only measure the spin of the particles but not actively change it at our will. Tom thinks that this might be possible in the near future. - - - Since information about both particles is stored virtually in the same location on this meta-information layer, changing the information about one particle would directly change also the information about its entangled partner.
Since the entangled partner in 3D reality is also only created based on information stored on the meta-information layer, its spin changes instantaneously in our 3D reality without any time delay whatsoever. No information is transfered between both particles within 3D reality. Since no information is transfered within 3D reality, relativity theory is not being violated. The key point here is that the information was transfered outside of 3D reality not inside of it.
No information is transfered between both particles within 3D reality. Since no information is transfered within 3D reality, relativity theory is not being violated. The key point here is that the information was transfered outside of 3D reality not inside of it.
We will now use the concept of a meta-information layer in combination with an analogy of a 3D computer game : Tom claims that in 3D reality objects only have to be rendered if our eyes can see them directly. The term rendered is used in the same sense as in a 3D computer game where objects are rendered in order to display them on the screen.
If in a 3D computer game our avatar is looking straight ahead he can not see any objects that are located behind him, so these objects do not have to be rendered. Only when our avatar turns around and looks in the opposite direction the objects that used to be behind him and thus were not visible to him enter his field of vision and thus have to be rendered.
So do objects still exist in the computer games reality, when they are behind our avatar ? Well they definitely exist on the level of information which in case of a computer game means in the working memory of our computer but they are not visible on the screen. In our 3D reality we are convinced that objects are always there, even if nobody is looking at them. But this is just an assumption, there is no way of knowing for sure.
If information on the meta information layer is changed, this can appear to us as if our physical 3D reality changed retrocausally. This is possible as long as no evidence within 3D reality exists - like data from a photon detector - which prohibits this from happening. Reality has to be consistent at all times and any evidence or data that exists within 3D reality must not lead to any contraditions.
Our perception that events have changed retrocausally is based on our assumption that reality is objective and exists independantly from us. If our 3D reality is not really objective but is created continiously based on information on the meta-information layer, then it can appear to us as if the deletion of the data of the photon detectors leads to a change of the measurement data of the screen - seemingly reaching backwards in time - when actually all that changed was data on the meta-information layer. And how does Tom explain the delayed choice quantum eraser experiment ?
Tom's explaination is that we are not living in an objective reality and that the photon reaching sensor D0 does not really have to decide immediately whether it should create an interference pattern or not. From a 3D reality viewpoint the result of the measurement of sensor D0 remains undeterminated until its partner photon reaches one of the sensors D1 to D4 and then the data of sensor D0 is determinated in a way that does not violate the consistency rules of reality.
We will never know that there was a short period of time where the result of the measurement was not available because we have no way of looking at this short gap in the data. The 3D reality created after this decision is made is based on data from the meta-information layer and it will have covered up the gap and filled it with consistent data.
If the partner photon hits sensor D3 or D4 the measurement of sensor D0 has to reflect the behaviour of a particle. If the partner photon hits sensor D1 or D2 the measurement of sensor D0 has to show an interference pattern. The key element here is that 3D reality has to be consistent with all data available within 3D reality. The measurement results of sensor D0 have to come out this way in order to be consistent with the measured data of sensors D1 to D4.
At this point it should be clarified that the phrase "the measurement collapses the probability distribution to a physical particle" has not really been accurate. Because if we consider Tom's model to be correct, everything is information only. Every conscious observer perceives 3D reality based on the information of the meta information layer and consistency of the experiences of all observers is guaranteed by ensuring consistency of the information their experience is based upon.
It is not easy to get our mind acquainted to this way of thinking, because we are so used to linear thinking and assuming that reality is objective. Even though this way of looking at the results of the double slit experiments can explain its strange results and behaviour, it will probably still take a long time until scientists are willing to open their minds to this new perspective.
500 years ago everybody was convinced that the earth was flat, will it take another 500 years until the idea that we are living in a virtual reality and that reality is not objective will be an accepted concept. Who knows, hopefully it wont take that long but until we get there, it might be your job to at least spend a few more minutes thinking about what you have just learned.
Information about all the events within 3D reality that you are learning about in the news might be interesting but information about reality itself might actually be important because if Tom's model of reality is correct, changing information on the meta information layer can change the 3D reality that is being created and within certain limitations everybody can access this meta information layer.
If you want to learn more about this, maybe take a look at Tom's lectures on Youtube or at his book that is available for free on Google books. Several short video segments with Tom have been collected in this article. All of Tom's information is available for free because Tom does not want to sell you any snake oil, he only wants to present you with a different way of looking at the world, because he knows from personal experience that this new viewpoint can be really empowering.
Comments
The only aspect with the experiment you're proposing that needs clarification is what happens to the data that is not looked at on the second day. If you keep it but just not look at it and then have someone look at the D0 data on the third day, the data that was not looked at but is still available would have an effect on the D0 data because consistency of both data sets must be ensured. You can't have all slit information available and still get an interference pattern as if all slit information is available you'll just end up with two dots.
As long as all you have is recorded data on a computer and there is no way for anyone to look at, the entire outcome of the experiment would remain in probability and by choosing what you do with the data (e.g. delete all slit information on the second day) you should end up with only an interference pattern when looking at D0 data on the third day. Whereas if you look at some slit data the second day but still keep the rest of the data, you should end up only with two dots. If you delete half of the slit data on the second day, you should see an interference pattern on the third day corresponding to the slit data you deleted and you should see two dots corresponding to the slit data you kept. This is an idea Tom has been talking about for a while but I'm not aware that this kind of an experiment has actually been done so it remains a hypothesis for now also the mechanism you use to delete data would have to be permament and reconstruction must not be possible, otherwise you would end up with inconsistencies .
Does this sound reasonable to you, or what am I missing?
Here is another article talking about the wrong interpretations of the quantum erasers:
www.mathblog.ellerman.org/2011/11/a-common-qm-fallacy/
So if at some point we found a way to actually control the state of entangled particles and could flip their spin at our will - which as far as I understand we currently can not - then this kind of tunneling of information might become possible by sending a binary code through spin-up / spin-down alterations.
There is a no communication theorem that Tom should have studied and all others and if somebody could prove with FTL that that theorem is wrong should speak up to help humanity:
en.wikipedia.org/wiki/No-communication_theorem
"They took the tapes out ... detectors detecting but not recording and they found out ..." and so on saying the same lies as Ross Rhodes
That's a lie because it never happened. He should have said "I think you would get this ..." not that "they got this"
I know that Tom may be didn't do it as trying to lie since he thought he was 100% right but yet he acted irresponsible and yet he lied but not making sure what the results are. Search the internet like I did and you won't find any information from any experiment where anybody noticed any difference on detectors not recording or recording. Yet Tom thinks that the rest of the world is wrong.
I like the fact that you are acting responsible about the information you supply. I wish others follow you (like Ross Rhodes and Tom).
Ross Rhodes has no background in science, only in acting and law as you can see in his public profile in LinkedIn:
www.linkedin.com/pub/ross-rhodes/9/7a5/481
And Tom just followed the conclusions from a lawyer.
Ross Rhodes wrote in bottomlayer.com/bottom/reality/chap2.html
He stated an "analysis" of things that happened, but they never happened, so they are all lies in that sense like:
1. Turn off the electron detectors at the slits. Suppose we take our modified double slit set up -- with electron detectors at the slits -- and leave everything intact. But, we will conduct the experiment with the electron detectors at the slits turned off, so that we will not actually detect any electrons at the slits.
The result upon analysis: an interference pattern at the back wall. So it seems that mere passage through the electron detectors at the slits does not affect the electron, so long as those electron detectors are not functioning.
2. Leave the electron detectors on, but don't gather the information. Suppose we take our modified double slit set up -- with electron detectors at the slits -- and still leave everything intact. And we will keep the electron detectors at the slits turned on, so that they will be doing whatever they do to detect electrons at the slits. But, we will not actually look at the count of electrons at the slits, nor will we record the count at the slits in any way, so that we will not be able to obtain any results from these fully-functioni ng electron detectors.
The result upon analysis: an interference pattern at the back wall. So it seems that the electron detectors located at the slits do not themselves affect the electron, even when the equipment is fully functioning and detecting (in a mechanical sense) the electrons, so long as we don't obtain the results of these measurements.
.. and so on like he mentions that a politician can later on choose the outcome of an experiment ... all very shocking conclusions but which are not true but yet completely taken as true by Tom
Since I portrayed these thought experiments as real experiments in my article and video I removed this particular aspect from the article and took down the video until I have time to redo the parts in question and also correct the D1-D4 only being event detectors aspect if the DCQE experiment.
I don't know if the words deceive and lie are really appropriate. Neither Tom nor Ross set out to mislead people but they have chosen to put the results of the DCQE experiment in a way that is only a thought experiment and has not been proven yet. Even Ron says in is lecture the "IF all entanglements could be undone the measurement would change" but he thinks they can not be undone. So we're again back to belief and we need real experiments. On one hand a real "deleting all double slit data permanently and looking at the screen" experiment and then Ron's EPR paradox experiment will really have to be done to know for sure if FTL communication is possible or not because if one photons gets changed on one side and the other one changes instantaneously then this method could be used as a FTL communication channel to transfer bits of information. Of which Ron says it won't work and Tom says it will work. The experiment does not seem to be that difficult to do so I hope someone will do it but who will if its results could put new questions on the table instead of removing existing ones
Still I would have never bothered to read any of those papers if I did not get hooked on the subject first by Tom/Ross's easily graspable metaphors. Deception might not quite be the right word... Did my 8th grade physics teacher also deceive me when he talked about the nucleus being a solid ball with solid electrons flying around it ? At grade 8 probability distributions are just too far out to grasp... It's all metaphors and some are useful for some time until they turn out to be not quite accurate.
You wrote: "Thanks for pointing out that paper. Had not seen it before. I just don't see where it would contradict Tom's interpretation. In chapter 3 the paper says that the whole "collapsing the wave function" thing is a wrong way of interpreting quantum mechanics and that "the measurement at one entangled particle changes the probabilities of the measurement for the other one". Isn't that exactly what Tom says ?"
As far as I know I don't see Tom ever talking about entanglement, it is something that he never mentioned in the recent thread in the board. Instead Tom apparently thinks that no matter the measurement, no matter the entanglement, what matters is the availability of information. Tom states a lie in the videos saying that people took the media out and then interference disappears, detectors not recording make the interference disappear. He follows the conclusion from Ross Rhodes (wrong conclusion) that if you don't record you get interference. I was pointing that error below with the quote from Wikipedia that you never get interference in D0, only in the correlations when observing the coincidences due to the entanglement. You can give it a try to see if you can find a paper talking about the influences of recordings in the outcomes of interference in a double slit. The first searches will just lead you to the discussions in the physicsforums.c om site where they say Ross Rhodes and Tom are wrong.
The latest paper says that the order does not matter, what matters is the math (which is the typical findings in papers), QM really follows math. If the order does not matter then why would it matter if the information is available (available when? before, after? it is irrelevant). But Tom will ignore so many things that point him wrong. I hope you can start at least having doubts.
Thank you for letting me give my opinions. Tom does not allow me to give mine in his forums, you can, not me. I don't want people to be deceived. I think QM is the output of a virtual reality, just without the errors that Tom states.
The paper uses a different language but the term "Nothing happens along these slices (horizontal lines of Figure 2)" and "implications on conditional probabilities hold for other measurements throughout the entire spacetime, present and past" Isnt that exactly what Tom's says about communication outside of 3D reality and the databases of the actualized past and probable future ?
In the conclusion the paper says "The lesson we draw here is that this very correlation between distant measurements does not feel their relative time ordering: it does not distinguish between future and past". Doesnt this sound again exactly like what Tom says when he speaks about the databases of the actualized past and probable future ? They exist outside of 3D-time-space. Where is the contradiction ? Its is different words saying the same thing.
The only thing is that the paper says in Figure 1 that WHY we see this behaviour is irrelevant. Isnt the WHY the key point we're trying to figure out ? Tom says WHY is because it is a virtual reality, because there are these databases, etc. The paper shows WHAT is happening and in the WHAT I see no contradiction to what Tom says. The question is WHY do we see this behaviour...
On Ron's math...I'm only an engineer and understood parts of it but I'm not familiar with the notation/symbol s used in QM so particularly in the information theory part I got lost.
Still Ron's conclusion that measurement = entanglement kind of makes sense to me and I had to smile at 54:12 when Ron says "We're a simulation running on a quantum computer". Isnt that again what Tom says ? So I'm actually starting to wonder if there is any real contradiction at all. In essence Tom and Ron come to the same conclusion, they just call it by different names.
I still think Ron's proposed EPRG paradox experiment should be done, because it would help to get to the bottom of the whole topic.
I think you are making a big mistake by reducing Ron Garret's exposure to the EPR paradox. I will give you more info on the EPR when I find more time. Did you follow the behavior of the polarizers in his exposure and the math explanation?
I think Tom is talking about the same experiment, since D1-D4 are not measuring position, only D0 does.
Here is also one of the papers that show the DCQE is not a big deal and the experiment does not prove at all that detectors not recording or erasing the recordings make any changes as Tom states (there is no experimental evidence to support his claims):
arxiv.org/pdf/1007.3977v1.pdf
I guess the EPRG paradox experiment that Ron Garret proposes at 25:50 of the video you referenced will have to be done to know for sure. If doing a measurment on the left changes interference on the right obviously there is faster than light communication which Ron simply dismisses as impossible. Tom would say that it is possible and explain it with the entangled particle communication outside of 3D reality. With Ron's attitude "we dont need to do this experiment as we know its results because faster than light communication is obviously impossible" we'll never find out. Ron's entire theory falls if this communication proven. I guess we can not know if Ron is right or Tom is right until somebody performs the EPRG paradox experiment...
"If the coincidence data is not collected or erased, then the idler photons are irrelevant to the experiment. Here are the results if you erase the coincidence data: since there is no "which way" information this experiment reduces to the regular double slit with no detector and D0 will show an interference pattern. All of the "D3 and D4 data" that would have ended up in piles behind each slit is now distributed in the interference pattern. Every particle that enters the apparatus ends up in a diffraction pattern lake any other DS experiment with no detector."
Can you trust an explanation from Tom that does not even know the results of the experiment and he predicts interference. If he would have at least studied the DCQE experiment like Jeff and me he would have at least known the actual results. Tom judgement is based only on which way information, ignoring the actual configuration of the experiment and the fact that the beam splitters create a different in phase of Pi. The following link explains the actual reason that Tom does not understand and keeps stating bigger errors:
www.youtube.com/watch?v=dEaecUuEqfc
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