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Why do you first say it is about the "which-way" information beeing somewhere in the universe that let the interference pattern collapse, but later call it observation and "if we watch".
Actually that is the only thing I don't like about this channel. There is a pause button in TH-cam. It is more convenient to use it compared to skipping it and missing some portions
It's kind of amazing that we're even able to conduct an experiment like this. We're "stuck" inside of a universe governed by these rules. Being able to peer into these rules while also being governed by them is almost like an eye looking at itself without a mirror. It's possible, if not likely, that there could be something even deeper, more "source code-ish", than these wave functions, that we'll never be able to observe. When expressed mathematically, there is very little difference between space and time. Yet to our experiences, they are easily distinguishable. This could be because they actually _are_ very different, or it could be that the universe we see is a limited projection of something deeper that we can only measure through conjecture. A classical analogy might be comparing the scientific discoveries and technological developments of two equally-intelligent beings: one that lives on land, and another that lives underwater. It is quite trivial for the land-dweller to conduct chemical experiments that require water, as well as experiments that must be done in the absence or near absence of water. But the aquatic species has a much greater challenge. Even very simple experiments, like mixing baking soda and vinegar, become much more difficult when you're under water. How do you get these chemicals in isolation in the first place, before mixing them? If a chemical reaction requires a flame, how much work is involved in making that happen in the underwater environment? Further, how much longer would it take the aquatic species to even observe fire in the first place, let along master it? Consider also experiments in electromagnetism. You would have to produce a non-conductive environment before you can even get to work putting conductors in it. In this real-world, classical analogy, there are solutions, because it is possible to leave the water and even bring air into the laboratory. But when it comes to quantum mechanics, our observable universe itself might be the water. Even in a perfect vacuum, even with materials at absolute zero, our experiments might be tainted by the nature of our universe.
Maybe you should train the cat to respond to which detector the particle went thru. Then if the experiment only responds to a human measurement, the cat could have the real answer to the question posed by this video. Would the results then change if the cat could signal the information to a human? Someone else probably thought of this before.
Well then, that would mean that the interference pattern would remain in place according to quantum theory. We had a cat like that once. It was also declawed on the front. Poor kitty!
It's the same in school. when the teacher isn't looking the student's actions become alle random and unpredictable, but if the teacher decided to look, the student's will be hard at work. ^^
Except when teacher decides to set up a hidden camera and he actually will be able to see all the unrelated actions without them knowing about observance. Quantum world is far more complicated. But have you ever noticed or felt weird sense of being watched by somebody else? In fact this phenomena is also from quantum world and some people even have this 6th sense developed so good so that they can instantly tell that somebody is watching spying on them, and it is quite easy to learn by anyone and experience quantum world in reality.
Arthur Vin soooooooooo true ..... I was a second grade teacher being evaluated on video and a student was dancing behind my back and I never knew until I saw playback video....
We are made up of quantas of unpredictability from quantum world. This gives us 6th sense, and it will always be unpredictable. Act of observation does affect physical measurement. In classical mechanics, observation does not affect to the extent it does in quantum world because quantum world is so tiny.
Of all videos in the Internet, this video gives the best explanation of the DCQE experiment. Most accurate, as well as comprehensible. Not easy to explain something complex in a field that one has been working on for perhaps decades, to layperson. Incredible.
This is hands down one of the most amazing pieces of information available on the Internet. What is nearly an incomprehensible topic explained so clearly that boggles the mind with its ramifications. You take your time with us so each sentence is really digested by the viewer. Great work Eugene
@@EugeneKhutoryansky The way you construct the ideas when you explain the notions tells about the way you structure them for yourself and this is something to thank for as well.
Except it's incorrect... Retrocausality is not possible we've known that for a while so not really amazing, there's plenty of crazy theories. Time doesn't even exist it's just something that exists in our minds, a tool we created to keep track of things, just like political laws don't really exist, I hope we can move forward beyond Einstein and his spacetime it's time to grow up already and quit playing around and solve the cosmology crisis and quit eating time with "beautiful" theories like string
In case, you have not already seen them, I also uploaded several other videos recently. As always, for each video that you like, you can help more people find it in their TH-cam search engine by clicking the like button, and writing a comment. Lots more videos are coming very soon. Thanks.
Huge fan of your videos Eugene. I have shown them to my professor and he was impressed, particularly with the ones pertaining to the visualization of mathematics. The work you do truly impacts my life and I am very grateful. Never stop spreading knowledge, it makes the world a better place.
Eugene Khutoryansky This answered a longstanding question that I've had. I always wondered if the shear act of measuring was collapsing the wave-function. This proves that it is NOT the measurement itself, but merely the fact that we KNOW information - which leads us all down the path of madness ;-) QM is truly absurd.
Eugene Khutoryansky Brilliant! Brilliant! Brilliant! Bravo! I loved it, this answered some questions raised from previous video on QM as well as tons and tons of other material I watched over the years on the subject. And raised a lot others.
That was a very creepy cat, but this is probably the most well-made video I have ever seen. It made an extremely difficult and non-intuitive topic relatively easy to follow and understand. Great job and I hope to see more like this!
Not really. Nothing about this intuitive especially with the strange cat animation acting as though the mere act of looking at a detector changea reality
FocusReborn So you won't remember most of the important points? What you should do is watch the video first and understand it, and THEN take a bong rip. Once your high, let your imagination wander.
Even if I never fully understand this experiment, I will continue to watch it for the cat. You know that it's not real and that it is just an assembly pixels, yet you still acknowledge it as a cat, wanting to see something less eerily false because your mind has convinced you that it is supposed to be something which it is not. A curious thing. 😵
This is a very interesting "reverse" variation of the Yoon-Ho Kim, Rong Yu, Sergei P. Kulik, and Yanhua Shih Delayed "Choice" Quantum Eraser. In the above video, the entangled pairs are created within the crystal photon detector. What is even more interesting, is that the experiment has both particle and wave behavior occurring simultaneously, and which state it is that you wish to view is determined by which "emitted photon" detector it is that you wish to monitor.
Eugene, congratulations for your fabulous videos! The way you present quantum phenomena is unique. I can understand the great effort required to do so. Especially I want to congratulate you for that: You enter into the essence of the concept - the nature - of observation, something many others avoid thoroughly.
Please someone explain to me how this isn't true: Say you have your double slit in your laboratory on Earth. Each gate has a photon-emitting crystal detector as shown in this video. The photons from the detectors are amplified and then beamed into space directly toward a Mars laboratory. Say Mars is 10 light minutes away. You activate your double slit at precisely 3:00:00. You have a prior arrangement with the astronaut in the Martian laboratory that he will choose to either insert the mirrors and erase the data (stripe pattern) or omit the mirrors and collect the data (collapse the wave function) at, say, precisely 3:09:59, one second before the light from your experiment reaches him from Earth. Wouldn't you already know at 3:00:01 which action he is going to take judging by which pattern appears on the wall behind your double slit on Earth? Couldn't you use this to communicate with him faster than light? What if he also had a double slit and you also had an eraser/detector setup, couldn't you then communicate across infinite distances instantaneously?
Nice thought! I may have an idea why this isn't true, but do note I'm new to this subject. I'm thinking if the Martian 'chooses' whether to insert or omit mirrors, the wave function collapses. It's no longer probability. If instead of choosing it was a probability, then it can't be used for communication. Right?
without the information from the detector, you won't be able to tell the difference between patterns. The blue and purple pattern you see is only formed by matching the data from the beam splitter with the wall.
You say you would already know which action he is going to take at 3:00:01, but that's not true. You already know it before that because of the prior arrangement. If you didn't make an arrangement, he would have to send his data back to earth, otherwise you wouldn't be able to recover any pattern... I think.
@14:30 This is called a Von Neumann Chain. The detectors do not collapse the superposition, but becomes entangled with it, also becoming a superposition, so the whole system will share a common wavefunction until an observation is made. For example: What would happen if we conducted the Schrodinger's Cat experiment inside another bigger box containing both the box with the cat, the scientist and another mechanism to kill the scientist (this is our eraser... haha) if the cat is found dead? The scientist's state would be entangled to the state of the cat, which would be entangled to the state of the radioactive particle, so the whole system would share a common wavefunction which would not collapse until someone from outside the system observe it. Now to blow our minds: What if we conducted this experiment with everyone in the world? Billions of boxes, one inside another, containing a person and a mechanism to kill that person if the previous was found dead? The system's wavefunction would only collapse if it is observed by outside the system. This has two solutions: or the system is never collapsed, what would mean that no one would actually be dead, but both dead and alive, even if the cat was found dead by the first scientist (a sort of solipsism, where the state of the "whole world" depends on you), or there is some sort of "omnipresent cosmic observer" which looks down at us to say we are alive or dead (a sort of theism). This is the Wigner's Friend Paradox.
+Matheus Adorni Dardenne The problem is that we can observe the cloth pattern BEFORE we decide whether to quantum erase or not (i.e., say the photons must travel an hour before they hit the beam splitters that erase the path information). In this case, since we have already observed the cloth, we know whether or not the wave function collapsed and can use the information to choose to erase or not erase, breaking down this whole system, it seems.
SteelBlueVision The crazyness of it is that whatever answer we observe on the cloth always correlates with our decision to erase the data or not. This is why some (like Wheeler) argue this experiment implies in retrocausation.
+Matheus Adorni Dardenne But, our decision to erase the data or not comes much later in time than our perception of the cloth. This creates a paradox, because our decision can intentionally be the opposite to what we see on the cloth.
+SteelBlueVision it can't, what we decide in the future will correlate with what the cloth shows. How can I put it; the pattern in the cloth is always incomplete until the other photon hits the detector, when it does, the sum of both patterns becomes the final result... we cannot see on the cloth what the decision will be on the future, it seems "ambiguous" until then, and corresponds both with the predictions of wave-like and particle-like behavior.
+Matheus Adorni Dardenne Sorry, but this doesn't make sense to me. What it sounds like you are saying is that the pattern on the cloth does not form until the photon's information is either revealed or erased. But there are four particles at play here, the photons which head off in their own direction and their corresponding larger particles which head for and are detected on the curtain. However, in my thought experiment, the larger particles hit the curtain first (in time), thus forming an interference pattern (or not) on the curtain. This happens > before already formed long ago < on the curtain 2) The curtain pattern changes > retroactively < based on what we decide to do with the photons (also a paradox of sorts?) It then appears to us that even though we had the intention to do the opposite, for some unexplainable reason we chose to act with the photons in a way that corresponds with what appeared on the curtain. We try again, and again, inexplicably, we decide to act with the photons in a way that corresponds with the curtain pattern instead of in contradiction to it. 3) The pattern on the curtain reflect what we will do in the future with the photons and once we see it, try as we might, we will only deal with the photons in a way that is compatible with the curtain pattern.
This is an excellent video. Part of an excellent series. Some of the videos in the series have explained things I've been trying to understand for a long time.
Pseudo That is a matter of considerable debate, and no one knows for sure. Any detector consists of particles which are also described by wave-functions, which don't seem to collapse until they are "observed."
Eugene Khutoryansky Isn't it more about our knowledge of the system rather than observation? As I understand it scientists use some kind of measuring device to measure which slit the particle goes through. So if you don't put a measuring device in front of the slits you'll get an interference pattern, but if you do put a measuring device in front of the slits to measure which slit it goes through you get that clump pattern instead. So, what would happen if you just placed your own two eyes in front of the slits instead of the measuring device? Wouldn't that be an observation too? But then again, your eyes wouldn't be able to see which slit the particle goes through since it's so tiny for us to see, so my prediction would be that if we placed our eyes in front of the slits instead of the measuring device we would get the interference pattern since our eyes can't really see which slit it goes through, hence why I think it's more about knowledge of the system rather than observation. So just by looking at the slits with your own eyes without any detectors/measuring device would NOT qualify as an observation. Am I correct or what, Eugene? What I'm trying to say is that the Delayed Choice Quantum Eraser Experiment shows that it isn't the detectors themselves which cause the wave function to collapse but rather that an observation of a conscious being that does it. So if you know which path the particles took which means you know which slit it went through the wave function collapses e.g. you get a clump pattern. But if you don't know which slit the particles went through you get the interference pattern. But what if a cat were to look at the data instead of a human? I've made the assumption that it's the knowledge of the system which causes the wave function to collapse. (You know which slit the particle went through, therefore the wave function collapses.) But since I would call a cat a concious being, what would happen if a cat were observing the data from the detector instead of a human? I would assume the cat doesn't know anything about the experiment, what it is, what it's all about, which slit the particle went through even if it looked at the data etc. So since the cat doesn't have the knowledge of which slit the particle went through, but is at the same time a conscious being, what would the cat see? Would the cat read something different out of the detector than we would do? Would the cat only see the interference pattern/read it out from the detector since it doesn't have the knowledge of which slit the particle goes through?
+Eugene Khutoryansky The problem is that the decision to "erase" can be made years after the particles have landed on that cloth. That is, whether or not beam splitters are employed can be really really delayed into those futures, so those photons travel for a very long time before the information contained within them is erased. In this case, what is the pattern on the cloth? Since it is formed before the choice of whether beam splitters will be employed to perform quantum erasure.
+mEPknuser "I've made the assumption that it's the knowledge of the system which causes the wave function to collapse. (You know which slit the particle went through, therefore the wave function collapses.)" Yes, you are correct. Its the case. Think about entanglement. If the other particle is to the opposite side of the universe, if you measure the one that is here, you automatically know the status, the reality of the other. Because the two particles, are one system, they are under the same wavefunction.
+Eugene Khutoryansky I have two questions about this video that seem most appropriate to ask in this reply thread. 1. If I understand correctly, a "Quantum Eraser" is essentially an array of reflecting mirrors placed in front of the two detectors/holes to allow for the possibility of the photon passing through either. It would seem then that for this to work, it must be functioning at the time of the experiment itself. How would one "activate" such a device after the fact when the photon/wave has already completed its journey past the point of the detector and through the two holes (or to phrase it perhaps more accurately, "done whatever it has done")? 2. I would also very much like to know what qualifies as an observation. If I understand the information you have presented correctly, it seems as if objects do NOT qualify, but living, thinking observers DO? Or am I misunderstanding? Would a computer recording the event count as an observer if the data on its drive was erased before anyone had the opportunity to look at it? I love your videos, and I thank you very much for making them! These are very difficult concepts to grasp for the uninitiated (people like me).
is that the quantum eraser send information back in time or is it that the particle is deciding after passing through the quantum eraser ? It seems to me it about the timing of the choice being made, not that the "eraser" is doing anything at all...
The Bigger question Ed is does that tree even exist whilst no one is there to observe it and are you just data in my universe till the day I observe you and materialize you into form...you exist in yours whilst you observe yourself, but how about your face and back side ? your not observing those right now ... :p *as Ed reaches round to grab his butt and check if he is real* :p
Thanks for the new video Eugene, ever since I heard about physicists at ANU doing this experiment I have wanted you to make a video on it to allow me to understand it better. Great job, love all your other videos too!
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Because from photon reference frame without rest-mass, there is no causality and all events happen simultaneously from the photon pov. Light speed is causality speed so as instantaneous as you can get. Not from outside inertial frame however (they appear to move lightspeed). Move interactions are physical interactions with another inertial frame so appear to obey causality. This experiment is NOT it is the photon's information being changed, its knowledge and not a material process. It must some how know its own wave function, or pilot wave as an informational omniscient thing...
okay, so it's not so much that the information is observed by a conscious mind, because the wave pattern drops when a detector is turned on regardless of whether a human being ever looks at the result of a detector. Instead, what collapses the wave function is if the information is simply available to the universe by way of entangled particles that can only behave a particular way as a particle if its "partner" is behaving in a particular way as a particle. Then again, maybe the system collapses if observed by the detector, despite the fact that the detector is not conscious. In any case, it seems that human observation is not what collapses the function if simply turning on a detector without looking at the detector result causes humans to observe the no interference pattern on the screen.
THIS. thank you. quantum mysticism gets on my tits and this business about consciousness needs stopping. 'observe' ah its a word, a different definition here, totally. following on from the uncertainty principle which talks about observation, how do you observe without interfering when the particle you use is equal in importance to things being observed and cant be divided. (although technically this experiment isnt uncertainty priciple, its observer effect, similar things really)
@boi detectors dont know anything because they are detectors not people. i dont quite understand the point you are making. a ball doesnt 'know' which angle to bounce, it just does it, its not that different.
All the music in this video is from the free TH-cam audio library, and the names of the songs are the following. Stale Mate William_Tell_Overture_by_Rossini 1812_Overture_by_Tchaikosvky
This channel is simply the best for me. A lot of channels illustrate complex concepts like this one, with fancier animations but for inexplicable reasons, this makes actual intellectual undestanding simpler for me. Thanks for the good work!
The pause between important information, as well as the 3D cat, helped more to understand this very difficult topic. Big thanks to the animator for making things basic!
14:32 So this means that there is a difference between a conscious observer like us and and an unconscious observer like the detector? That question is on my mind for quite some time now, does the universe differentiate between consciousness and "non-consciousness" ? Wouldn't that mean that without consciousness there cannot be a definite reality? Hmmm this was probably asked by so many people, what do you think of this? edit: okay i just finished the video, should have waited to ask that question since it is mentioned at the end :D hopefully you will adress this kind of stuff in the future videos
niv skillsurf Whether or not consciousness makes a difference is a matter of debate. There are a number of different philosophical interpretations of Quantum Mechanics. One of them states that a wave-function collapses when it is observed by a conscious observer. The other interpretations have a different explanation. And yes, as you said, I plan to eventually make a video that addresses the different philosophical interpretations.
There is no reason to assume Consciousness has anything to do with it when you entanglement I don't think. You could just say we only see the wave function we entangle with
niv Gnasherus The detectors aren't doing reading. The detectors have to be read by a recording device. Once that happens, the quantum wave collapses. In the real Delayed Choice Quantum Eraser experiment photons are hitting the screen or the detectors at a rate too fast for humans to decide whether or not to read a detector. Fast processors are implementing software to record no not record through which slit the entangled photon and it's entangled partner that hit the screen earlier in time. We can only play back the recording and match entangled particles. From the recording, we see that when it is known through which slit a photon passes, the photon hitting the screen acts like a particle. From the recording, we see that when it is not known through which slit a photon passes, the photon hitting the screen acts like a wave. There is no human consciousness involved. Quantum entanglement appears to break distance and convey information faster than the speed of light, instantaneously. Quantum entanglement appears to break time and convey information backward in time. Three years after this video,I have seen no papers that can satisfactorily tidy up this mess. A decision in the present causes an outcome in the past. 😖😖😖😖😖
@@khaledyasser8293 We do have a reason to assume consciousness is at play because the primary variable in this experiment is knowledge of how its set up.
Theenerd ジェームズ Thanks again for the compliment. I am glad that you love my explanations, and that they are helpful. And yes, lots more videos are on their way.
I really enjoy your videos. I would like to just make a comment about the music selection though. I think it would be VERY impactful if you choose darker music. Much of the "happy" major songs seem to take away from the awe-inspiring effect your videos generally leave upon a person. I see you use music form the Audio Library of TH-cam. If you choose more music from the Dark category (Classical and Ambient are usually the best of the dark genre), music more abstract and maybe even a little disturbing, I think you could greatly enhance the quality of your videos and add a uniqueness factor to your videos (All of the commercial industry already uses happy ukulele songs, you should avoid doing that). If you add this dimension to your videos (haunting music with awe-inspiring physics revelations), I believe you could gain a cult following. I with you the best with your channel and I hope you consider my suggestion.
I'm so glad this video talks about the very fundamental concepts and I think this is the only one I've seen so far which has explained "What erasing of information means", I've been quite confused about it in the other videos which just seem to mention it without really explaining clearly. Thank you!
Thanks, Eugene, another fabulous video--and I'll be re-watching this one more than a few times. Some videos on physics feature narrators who talk really fast--possibly to sufficiently engage attention. I love it that your narrator talks at a normal pace with lots of pauses and sometimes repetitions to allow me to absorb the ideas. Your music and animations do the engaging. And, of course, the animations often help with visualizing. This is a brilliant and unique approach. I wish other video makers understood this.
+Alexandra Hopkins, thanks for the compliment. I am glad that you like the video, and the pace of the narrations. And thanks for the compliments on the animations.
+Alexandra Hopkins -- the fast ones that I despise, are the ones where they finish the video and then edit out the small pauses between sentences/paragraphs. Thus it becomes just one endless no pause nightmare.
Here is the problem. To be an observer one must be conscious. But, we don't know what consciousness is so we don't know what an observer is either. Since we don't know what consciousness is we can't say for certain that that the particles themselves are not conscious. If the particles are conscious, they may change the way the mind perceives the patterns they make.
Steve Bergman How so? It seems to me one of two possible things happen in this scenario 1 - Consciousness - meaning the awareness that some event has taken place - causes the "rest" of the event to also materialize, in the sense that if a particle is measured at a given point, it must have traversed through a certain path to get there, or 2 - All the events have been laid out in advance as an infinite set of possibilities, and when observation - or just the mere fact that an event has taken place - "forces" the event into existence in its entirety. That, however, would imply that time is only a dimension we travel through, and everything that ever was or will be was "created" instantaneously before even the first ever event to take place in our universe. Seems to me like both scenarios imply the existence of consciousness, either within or outside the system. In the first scenario, the universe would be the consciousness I'm referring to. In the second scenario, an outside consciousness would have "created" the entire set of possibilities and then set it in motion. What am I missing?
First of all I would like to say that I think your videos are absolutely fantastic. Except the two about quantum mechanics. You really make it seem like consiousness has some important role in the double slit experiment, which is definitely not the consensus by physicists. Im not sure if you really believe that or if it is a mistake by my part from interpreting the video, but you unfortunately make it look like it (a lot of youtube videos do) for example when the cat is closing its eyes and the results change. "Observing" in quantum mechanics does not mean "consious beeing observing". I believe interfere or disturb is a better word to avoid confusion.
Andreas Henriksson I also thought that consiousness had nothing to do with it, but how can it then be that the wave function does not collapse by measuring, but only by the information that the measurement produces? (As shown by the use of a quantum eraser) Khutoryanski already promised a video about the phylosophical concequences of this.
Andreas Henriksson There are a number of different philosophical interpretations of Quantum Mechanics. One of them is, in fact, the idea that the wave function collapses only when a conscious observer observes it. There are also many other interpretations of Quantum Mechanics, where consciousness does not play a role. However, all these other interpretations have to explain why the data makes it seem as if consciousness is involved. In my videos on Quantum Mechanics, I leave this as an open question, and I only state that it "seems" as if consciousness plays a role. I never explicitly state whether it does or doesn't, as this is a matter of debate, and no on really knows for sure when or how the wave-function collapses.
Eugene Khutoryansky Yes, there is a number of different philosophical interpretations of Quantum Mechanics, and one of the more unpopular (by physicist) and silly ideas is the idea that consciousness plays a role - an idea often used by new-age people and such who misuse Quantum mechanics to fit their own view. What counts as consciousness? can a toddler collapse the wave function, a chimpanzee? dog? insects? This obviously creates some ridiculous problems (and its actually quite arrogant to believe that we humans possess a special ability to collapse the wavefunction..) And I do not agree that the data seems as consciousness has something to do with it, just that your explanation of the problem make it look that way ;) As a matter of fact I have never heard of any physicists that believe in this interpretation (Im a physics student, and have asked my professors about this) I know you never explicitly stated anything, but you sure emphasized this very disfavored interpretation.
Andreas Henriksson All I am doing is leaving open the possibility that consciousness plays a role, without stating whether it does or doesn't, as there is presently no way to prove this one way or the other. Also, I think that the percentage of physicists who think that consciousness plays a role might actually be higher than you think, though they would disagree with each other over what counts as consciousness. In any case, the biggest issue I see for the view that consciousness plays a role is the question of what the Universe was doing before there were conscious observers in it, such as before any planets had yet formed in the Universe to support life.
Andreas Henriksson You are not considering that, maybe, consciousness has something to do. I am not by far instructed at quantum mechanics but using the logic that my knowledge in programming has granted me I can take a shot at it. This is that maybe our "consciousness" is like a system that kind of constructs a solid experience through the possible quantum outcomes so we can actually be self aware of our existence. I mean if you try really hard to think what consciousness is you will realize that it is way beyond understanding; it is like trying to see the back of your head in a place with no reflective surfaces. So what I'm trying to say is that maybe the Universe, time, space, and all energy and particles make no sense and are not correlated at all but our consciousness (which I think might be created by the way the particles in our brains are set up) is so complex that can make everything make sense among the quantum chaos and make us feel, well, conscious.
Any talk of the content of human consciousness being the deciding factor of whether or not "reality" is real is obvious nonsense! There is something fundamental that we have not understood
Here is my opinion. I don't think human consciousness is the deciding factor, but the fact that the information of the experiment exists somewhere in the universe. It can be registered on a sheet of paper, a hard drive or a brain. It looks like we are also entangled with the whole experiment.
I agree. It's very suspicious that this experiment is so accepted among prominent thinkers. The blind jump from physics to philosophy is obscene. Physics has something to gain as does philosophy. Very politicized.
I have sen this experiment described in a different way and I am wondering if it has been done in this way. Particle detectors are put on each slit. The date from the particle detectors goes into a computer and no one sees them until later. Photographic plates are used. The experiment is run multiple times with the particle detectors turned on each time. The plates are developed and fixed. Nobody looks at the plates until two weeks after the experiment. A that time no one has seen either the plates or the results in the computer. Now the computer randomly picks half the experiments and erases the results. When the data is looked at the results for each experiment that had the detector data erased shows an interference pattern on the plates and the ones for which the particle detector data was kept show the pattern of individual particles. Has this experiment ever been done? Could it be done?
Does the two slit experiment need to be done in a vacuum in case the air in the room interacts with the particle therefor theoretically you could figure out which slit the particle went through? Or on a different scale, don't particles cause gravity so theoretically you can measure the particles gravitational wave effects somehow and determine which slit it went through? In that case you wouldn't really be affecting or touching the particle as it flies through the slit? I'm trying to think of a way you might theoretically detect something without actually disturbing it.
In the delayed eraser double-slit experiment, if they have a video camera looking at the detector data, instead of the scientist, and the scientist erase the detector data before looking at it, will they see a diffraction pattern or a two lines on the screen? If they see the diffraction pattern and then look at the footage from the camera and then look at the screen again will it change to two lines? If they see two lines but decide to delete the video before watching it will it change to a diffraction pattern?
Just one question: Why is the blue striped pattern skewed to the left (yellow detector) and purple to the right (towards the green detector) instead of vice versa?
What are the limitations of the quantum eraser? Does it still restore the interference pattern if we endow the photons emitted by one crystal with another certain property (say, a specific polarisation)? Is the result of that the same, if the four final detectors for the photons measure not only light, but also polarisation?
At 22:50, there are 2 cases out of 4 where we can tell form which hole particle passes. Here also we get interference pattern(as per video). what will happen if we go on increasing this possibility.like ,8 out of 10 ....or 98 out of 100 cases we know (which mean almost all the time we know).will there be interference pattern ? or it will be dark two strips with light interference ?
What if when the electron passes through the cristal, it gets itself entangled with the photon that is emitted? So when the photon is measured, it "passes the information" instantly to the electron that created it, then the pattern instantly colapses to a wave-like pattern or a particle-like pattern (depending on whether the quantum eraser was activated or not), even though they have already passed through the detector, forming the four possible patterns that overlap (as shown in the video). Does it make any sense?
can we alter the path such that the path is known once it has been been determined that pattern is interference formed by wave........suppose we have decided to activate the quantum eraser and we observe striped pattern but the entangled pair of the particles, or photons emitted via detector still has to reach the photon detector........now by observing the results it can be known that the path that will be taken by photons would make it impossible to determine which hole it passes......suppose if i elongate the path significantly which then allows me to rig the experiment........say a step deactivating or nullifying the results of an eraser making the path determinable? Can we rig the experiment once we have obtained the stripped pattern result??
So what happens if one looks at the cloth to notice two xor more stripes, and then activates the quantum eraser (agreed beforehand to be executed several light-seconds away)?
I don't understand about there being two offset possibilities of a striped wave interference pattern. How is that the two different offset patterns can emerge? Have I missed something? Also, does this mean that if we shoot many particles through the slits without the detectors present, it will always eventually add up to a non-interference pattern because the two offset patterns will combine to that? I don't think that's the case as when I used a laser light to shine through multiple slits there was always an interference pattern. So what's that about?
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Why do you first say it is about the "which-way" information beeing somewhere in the universe that let the interference pattern collapse, but later call it observation and "if we watch".
Not a subtitle suggestion, rather just the thought that the script might want to say “equally possible” at 20:47
Terima kasih.
I like the fact that you pose for 5 seconds between the sentences. It gives me time to think about what you just said. Keep up the good work.
Thanks.
Actually that is the only thing I don't like about this channel.
There is a pause button in TH-cam.
It is more convenient to use it compared to skipping it and missing some portions
@@the_sophile there is playback speed button in youtube, which allows you to change the running speed of a video
True, I love that!
It's too slow for the average person, I'd say. Certainly not done to lengthen the video, I'm sure
It's kind of amazing that we're even able to conduct an experiment like this. We're "stuck" inside of a universe governed by these rules. Being able to peer into these rules while also being governed by them is almost like an eye looking at itself without a mirror.
It's possible, if not likely, that there could be something even deeper, more "source code-ish", than these wave functions, that we'll never be able to observe. When expressed mathematically, there is very little difference between space and time. Yet to our experiences, they are easily distinguishable. This could be because they actually _are_ very different, or it could be that the universe we see is a limited projection of something deeper that we can only measure through conjecture. A classical analogy might be comparing the scientific discoveries and technological developments of two equally-intelligent beings: one that lives on land, and another that lives underwater.
It is quite trivial for the land-dweller to conduct chemical experiments that require water, as well as experiments that must be done in the absence or near absence of water. But the aquatic species has a much greater challenge. Even very simple experiments, like mixing baking soda and vinegar, become much more difficult when you're under water. How do you get these chemicals in isolation in the first place, before mixing them? If a chemical reaction requires a flame, how much work is involved in making that happen in the underwater environment? Further, how much longer would it take the aquatic species to even observe fire in the first place, let along master it? Consider also experiments in electromagnetism. You would have to produce a non-conductive environment before you can even get to work putting conductors in it.
In this real-world, classical analogy, there are solutions, because it is possible to leave the water and even bring air into the laboratory. But when it comes to quantum mechanics, our observable universe itself might be the water. Even in a perfect vacuum, even with materials at absolute zero, our experiments might be tainted by the nature of our universe.
(Kind) Wisdom very intelligent prose (prose is a talented writing) wisely stated
Shrodinger's cat looks happy that she's not the object of this experiment.
+Austin Geary she also *is* the object of this experiiments.
Maybe you should train the cat to respond to which detector the particle went thru. Then if the experiment only responds to a human measurement, the cat could have the real answer to the question posed by this video. Would the results then change if the cat could signal the information to a human? Someone else probably thought of this before.
@@conniejurgs9427 Castrated cat WILL NEVER cooperate with human being, therefore it won't respond to your answer. LOL.
Well then, that would mean that the interference pattern would remain in place according to quantum theory. We had a cat like that once. It was also declawed on the front. Poor kitty!
Hmm
It's the same in school. when the teacher isn't looking the student's actions become alle random and unpredictable, but if the teacher decided to look, the student's will be hard at work. ^^
Except when teacher decides to set up a hidden camera and he actually will be able to see all the unrelated actions without them knowing about observance. Quantum world is far more complicated. But have you ever noticed or felt weird sense of being watched by somebody else? In fact this phenomena is also from quantum world and some people even have this 6th sense developed so good so that they can instantly tell that somebody is watching spying on them, and it is quite easy to learn by anyone and experience quantum world in reality.
Yeah that being watched feeling phenomenon would be quite cool if it wasn't faulty.
Made my day, after 2years
Arthur Vin soooooooooo true ..... I was a second grade teacher being evaluated on video and a student was dancing behind my back and I never knew until I saw playback video....
We are made up of quantas of unpredictability from quantum world. This gives us 6th sense, and it will always be unpredictable. Act of observation does affect physical measurement. In classical mechanics, observation does not affect to the extent it does in quantum world because quantum world is so tiny.
Of all videos in the Internet, this video gives the best explanation of the DCQE experiment. Most accurate, as well as comprehensible. Not easy to explain something complex in a field that one has been working on for perhaps decades, to layperson. Incredible.
Thanks for the compliment about my explanation.
This is hands down one of the most amazing pieces of information available on the Internet. What is nearly an incomprehensible topic explained so clearly that boggles the mind with its ramifications. You take your time with us so each sentence is really digested by the viewer. Great work Eugene
Thanks for the compliments.
@@EugeneKhutoryansky The way you construct the ideas when you explain the notions tells about the way you structure them for yourself and this is something to thank for as well.
Except it's incorrect... Retrocausality is not possible we've known that for a while so not really amazing, there's plenty of crazy theories. Time doesn't even exist it's just something that exists in our minds, a tool we created to keep track of things, just like political laws don't really exist, I hope we can move forward beyond Einstein and his spacetime it's time to grow up already and quit playing around and solve the cosmology crisis and quit eating time with "beautiful" theories like string
In case, you have not already seen them, I also uploaded several other videos recently. As always, for each video that you like, you can help more people find it in their TH-cam search engine by clicking the like button, and writing a comment. Lots more videos are coming very soon. Thanks.
Huge fan of your videos Eugene. I have shown them to my professor and he was impressed, particularly with the ones pertaining to the visualization of mathematics. The work you do truly impacts my life and I am very grateful. Never stop spreading knowledge, it makes the world a better place.
Logan Retamoza Eugene has a very special way of explaining things. Even this video is mind-blowing.
Eugene Khutoryansky This answered a longstanding question that I've had. I always wondered if the shear act of measuring was collapsing the wave-function. This proves that it is NOT the measurement itself, but merely the fact that we KNOW information - which leads us all down the path of madness ;-) QM is truly absurd.
Eugene Khutoryansky Brilliant! Brilliant! Brilliant! Bravo! I loved it, this answered some questions raised from previous video on QM as well as tons and tons of other material I watched over the years on the subject.
And raised a lot others.
By using the beam splitters we erase information from which detector we want it to detect the photon.
That was a very creepy cat, but this is probably the most well-made video I have ever seen. It made an extremely difficult and non-intuitive topic relatively easy to follow and understand. Great job and I hope to see more like this!
Not really. Nothing about this intuitive especially with the strange cat animation acting as though the mere act of looking at a detector changea reality
@@Berniebud Hi. May i recommend you; a science-youtube-fan;
some more science-youtuber?
@@Berniebud The cat is very important
The cat's creepiness was needed to kinda erase the multiple questions from each fact, to not block more information 😁
Dammit i told you the universe wasn't ready for offical release yet.
It doesn't show any programming bugs in this one. I'll say it works perfectly. Just doing the math algorithms, only when necessary.
Eugene, you posses a very unique and effective view of the pedagogical approach needed for a gradual explanation of these phenomena.
Giovanni Andreani Thanks for the compliment.
Now's a good time to get my bong out
FocusReborn So you won't remember most of the important points? What you should do is watch the video first and understand it, and THEN take a bong rip. Once your high, let your imagination wander.
I like the way you think.
+Alexandro Ochoa Me too!
+Alexandro Ochoa I find that THC helps me concentrate. If I were sober I probably wouldn't have paid full attention to the whole video.
after a dessert of shroms
Mind = Blown, or least I think, I haven't observed it yet to confirm...
Even if I never fully understand this experiment, I will continue to watch it for the cat. You know that it's not real and that it is just an assembly pixels, yet you still acknowledge it as a cat, wanting to see something less eerily false because your mind has convinced you that it is supposed to be something which it is not.
A curious thing. 😵
This has got to be one of the best explanations for the Delayed Choice Quantum Eraser. Thank you :)
This is a very interesting "reverse" variation of the Yoon-Ho Kim, Rong Yu, Sergei P. Kulik, and Yanhua Shih Delayed "Choice" Quantum Eraser. In the above video, the entangled pairs are created within the crystal photon detector. What is even more interesting, is that the experiment has both particle and wave behavior occurring simultaneously, and which state it is that you wish to view is determined by which "emitted photon" detector it is that you wish to monitor.
my mind is in a superposition of blown and confused
Welcome to the club...🤔
Oh my god! That was hands down the best explanation I never came across in my life. Thank you!
Thanks for the compliment about my explanation.
Chaitanya kumar Try Tom Campbell.
Eugene, congratulations for your fabulous videos! The way you present quantum phenomena is unique. I can understand the great effort required to do so. Especially I want to congratulate you for that: You enter into the essence of the concept - the nature - of observation, something many others avoid thoroughly.
Thank you for keeping up these videos, for me this is the best explanation
jeez, the universe is so troll
Bohr is the fucking troll. He was a fucking idealist. Check out pilot wave theory or Bohmian mechanics.
@@BlingSco you are a Physics noob. Or worse, a Physics troll.
@@BlingSco Bohemian mechanics are the best.
As always, great work Eugene.
My brain wasn't ready for this. Amazing stuff. Thank you.
Please someone explain to me how this isn't true:
Say you have your double slit in your laboratory on Earth. Each gate has a photon-emitting crystal detector as shown in this video. The photons from the detectors are amplified and then beamed into space directly toward a Mars laboratory. Say Mars is 10 light minutes away. You activate your double slit at precisely 3:00:00. You have a prior arrangement with the astronaut in the Martian laboratory that he will choose to either insert the mirrors and erase the data (stripe pattern) or omit the mirrors and collect the data (collapse the wave function) at, say, precisely 3:09:59, one second before the light from your experiment reaches him from Earth. Wouldn't you already know at 3:00:01 which action he is going to take judging by which pattern appears on the wall behind your double slit on Earth? Couldn't you use this to communicate with him faster than light? What if he also had a double slit and you also had an eraser/detector setup, couldn't you then communicate across infinite distances instantaneously?
Nice twist :)
Nice thought!
I may have an idea why this isn't true, but do note I'm new to this subject.
I'm thinking if the Martian 'chooses' whether to insert or omit mirrors, the wave function collapses. It's no longer probability. If instead of choosing it was a probability, then it can't be used for communication. Right?
without the information from the detector, you won't be able to tell the difference between patterns. The blue and purple pattern you see is only formed by matching the data from the beam splitter with the wall.
You say you would already know which action he is going to take at 3:00:01, but that's not true. You already know it before that because of the prior arrangement.
If you didn't make an arrangement, he would have to send his data back to earth, otherwise you wouldn't be able to recover any pattern... I think.
You can't erase the information after the particles hit the cloth, therefore, you'll never observe a stripped pattern.
@14:30
This is called a Von Neumann Chain. The detectors do not collapse the superposition, but becomes entangled with it, also becoming a superposition, so the whole system will share a common wavefunction until an observation is made.
For example:
What would happen if we conducted the Schrodinger's Cat experiment inside another bigger box containing both the box with the cat, the scientist and another mechanism to kill the scientist (this is our eraser... haha) if the cat is found dead? The scientist's state would be entangled to the state of the cat, which would be entangled to the state of the radioactive particle, so the whole system would share a common wavefunction which would not collapse until someone from outside the system observe it.
Now to blow our minds:
What if we conducted this experiment with everyone in the world? Billions of boxes, one inside another, containing a person and a mechanism to kill that person if the previous was found dead? The system's wavefunction would only collapse if it is observed by outside the system. This has two solutions: or the system is never collapsed, what would mean that no one would actually be dead, but both dead and alive, even if the cat was found dead by the first scientist (a sort of solipsism, where the state of the "whole world" depends on you), or there is some sort of "omnipresent cosmic observer" which looks down at us to say we are alive or dead (a sort of theism).
This is the Wigner's Friend Paradox.
+Matheus Adorni Dardenne The problem is that we can observe the cloth pattern BEFORE we decide whether to quantum erase or not (i.e., say the photons must travel an hour before they hit the beam splitters that erase the path information). In this case, since we have already observed the cloth, we know whether or not the wave function collapsed and can use the information to choose to erase or not erase, breaking down this whole system, it seems.
SteelBlueVision The crazyness of it is that whatever answer we observe on the cloth always correlates with our decision to erase the data or not. This is why some (like Wheeler) argue this experiment implies in retrocausation.
+Matheus Adorni Dardenne But, our decision to erase the data or not comes much later in time than our perception of the cloth. This creates a paradox, because our decision can intentionally be the opposite to what we see on the cloth.
+SteelBlueVision it can't, what we decide in the future will correlate with what the cloth shows. How can I put it; the pattern in the cloth is always incomplete until the other photon hits the detector, when it does, the sum of both patterns becomes the final result... we cannot see on the cloth what the decision will be on the future, it seems "ambiguous" until then, and corresponds both with the predictions of wave-like and particle-like behavior.
+Matheus Adorni Dardenne Sorry, but this doesn't make sense to me. What it sounds like you are saying is that the pattern on the cloth does not form until the photon's information is either revealed or erased. But there are four particles at play here, the photons which head off in their own direction and their corresponding larger particles which head for and are detected on the curtain.
However, in my thought experiment, the larger particles hit the curtain first (in time), thus forming an interference pattern (or not) on the curtain. This happens > before already formed long ago < on the curtain
2) The curtain pattern changes > retroactively < based on what we decide to do with the photons (also a paradox of sorts?) It then appears to us that even though we had the intention to do the opposite, for some unexplainable reason we chose to act with the photons in a way that corresponds with what appeared on the curtain. We try again, and again, inexplicably, we decide to act with the photons in a way that corresponds with the curtain pattern instead of in contradiction to it.
3) The pattern on the curtain reflect what we will do in the future with the photons and once we see it, try as we might, we will only deal with the photons in a way that is compatible with the curtain pattern.
The 5 second delay between sentences is killing me
+aroseland1 fast forward , video speed 1.25 .
5 seconds quantumlly erased
Watch at double speed and read the captions.
Watch at double speed and read the captions.
The background music is a distraction too.
I really love your quantum science videos. I am so glad you are going to make another one.
space laser dank raccoon Thanks. I am glad to hear that you love my quantum videos.
This is an excellent video. Part of an excellent series. Some of the videos in the series have explained things I've been trying to understand for a long time.
Are the speech pauses to allow time for information to travel backwards through time?
So, that MUST be Schrodinger's cat, right?
Yes, that is Schrodinger's cat. He makes appearances in many of my videos.
@@EugeneKhutoryansky 🤣🤣🤣🤣
Another great lecture. It's amazing how Theoretical physics is yielding such good communicators.
I think this is one of your best. I look forward to seeing your next masterpiece when it comes out :)
pendalink Glad you liked it. Lots more videos are on their way.
4:10 - 4:25
... according to my calculations: in order for the experiment to work, we must kill the cat.
🐱
The creepiest cat I have ever seen
It's the quantum cat. Everybody recognizes her.
at 11:29 i started thinking that a bunch of hunters had it with its creepiness and were after its head.
The cat is stressed out by 80 years of rumors of having his life threatened.
that is a shrodingers cat.. 🐈
This is what happens when a cat is both alive AND dead at the same time...
Thank you for these wonderful videos!
Still blows my mind as it did 7 years ago,love your channel
Thanks.
What exactly qualifies as observation?
Pseudo That is a matter of considerable debate, and no one knows for sure. Any detector consists of particles which are also described by wave-functions, which don't seem to collapse until they are "observed."
Eugene Khutoryansky Isn't it more about our knowledge of the system rather than observation?
As I understand it scientists use some kind of measuring device to
measure which slit the particle goes through. So if you don't put a
measuring device in front of the slits you'll get an interference
pattern, but if you do put a measuring device in front of the slits to
measure which slit it goes through you get that clump pattern instead.
So, what would happen if you just placed your own two eyes in front of
the slits instead of the measuring device? Wouldn't that be an
observation too?
But then again, your eyes wouldn't be able to see which slit the
particle goes through since it's so tiny for us to see, so my prediction
would be that if we placed our eyes in front of the slits instead of
the measuring device we would get the interference pattern since our
eyes can't really see which slit it goes through, hence why I think it's
more about knowledge of the system rather than observation.
So just by looking at the slits with your own eyes without any detectors/measuring device would NOT qualify as an observation.
Am I correct or what, Eugene?
What I'm trying to say is that the Delayed Choice Quantum Eraser Experiment shows that it isn't the detectors themselves which cause the wave function to collapse but rather that an observation of a conscious being that does it. So if you know which path the particles took which means you know which slit it went through the wave function collapses e.g. you get a clump pattern. But if you don't know which slit the particles went through you get the interference pattern.
But what if a cat were to look at the data instead of a human? I've made the assumption that it's the knowledge of the system which causes the wave function to collapse. (You know which slit the particle went through, therefore the wave function collapses.) But since I would call a cat a concious being, what would happen if a cat were observing the data from the detector instead of a human? I would assume the cat doesn't know anything about the experiment, what it is, what it's all about, which slit the particle went through even if it looked at the data etc. So since the cat doesn't have the knowledge of which slit the particle went through, but is at the same time a conscious being, what would the cat see? Would the cat read something different out of the detector than we would do?
Would the cat only see the interference pattern/read it out from the detector since it doesn't have the knowledge of which slit the particle goes through?
+Eugene Khutoryansky The problem is that the decision to "erase" can be made years after the particles have landed on that cloth. That is, whether or not beam splitters are employed can be really really delayed into those futures, so those photons travel for a very long time before the information contained within them is erased. In this case, what is the pattern on the cloth? Since it is formed before the choice of whether beam splitters will be employed to perform quantum erasure.
+mEPknuser "I've made the assumption that it's the knowledge of the system which
causes the wave function to collapse. (You know which slit the particle
went through, therefore the wave function collapses.)"
Yes, you are correct. Its the case. Think about entanglement. If the other particle is to the opposite side of the universe, if you measure the one that is here, you automatically know the status, the reality of the other.
Because the two particles, are one system, they are under the same wavefunction.
+Eugene Khutoryansky I have two questions about this video that seem most appropriate to ask in this reply thread.
1. If I understand correctly, a "Quantum Eraser" is essentially an array of reflecting mirrors placed in front of the two detectors/holes to allow for the possibility of the photon passing through either. It would seem then that for this to work, it must be functioning at the time of the experiment itself. How would one "activate" such a device after the fact when the photon/wave has already completed its journey past the point of the detector and through the two holes (or to phrase it perhaps more accurately, "done whatever it has done")?
2. I would also very much like to know what qualifies as an observation. If I understand the information you have presented correctly, it seems as if objects do NOT qualify, but living, thinking observers DO? Or am I misunderstanding? Would a computer recording the event count as an observer if the data on its drive was erased before anyone had the opportunity to look at it?
I love your videos, and I thank you very much for making them! These are very difficult concepts to grasp for the uninitiated (people like me).
25:27 revenge of the Shrodinger's cat?
Nice vid. I love the cat so please keep him/her around for the future quantum videos.
+9009Hayden, thanks. And yes, the cat will always stay alive and healthy for future videos.
+Physics Videos by Eugene Khutoryansky phew...
+Physics Videos by Eugene Khutoryansky Just don't let that Schrödinger guy around him. If you do, you'll never know what could happen to him
NyteMunkey XD
A huge thanks for your videos. I have wanted to have something in-depth like this for a good while.
Thanks. I am glad you like my videos.
is that the quantum eraser send information back in time or is it that the particle is deciding after passing through the quantum eraser ? It seems to me it about the timing of the choice being made, not that the "eraser" is doing anything at all...
So if a tree falls in the forest, and no one is there, does it make it sound?
The Bigger question Ed is does that tree even exist whilst no one is there to observe it and are you just data in my universe till the day I observe you and materialize you into form...you exist in yours whilst you observe yourself, but how about your face and back side ? your not observing those right now ... :p *as Ed reaches round to grab his butt and check if he is real* :p
That cat is far more stranger than quantum mechanics ^_^
I kept wondering if it was supposed to be Schrödinger’s or if the narrator is a serious cat lady.
Cat catter cattest
The clarity and precision of the English voice-over is exceptional which give even more value to this extra-ordinary video.
Thanks for the compliments.
Thanks for the new video Eugene, ever since I heard about physicists at ANU doing this experiment I have wanted you to make a video on it to allow me to understand it better. Great job, love all your other videos too!
blake301987 Thanks. I am glad that you liked this video, and all my other videos too. Lots more are on their way.
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Thanks.
so..if I jump of a really high building with my eyes closed?....
I hypothised a future pridictor using this
Music name till 2:25???
How can I communicate with you?
@@user-sm9yg8sr1l ??to whom..
im thinking this is more about how mass, space and time are tied together than wave particle duality
Because from photon reference frame without rest-mass, there is no causality and all events happen simultaneously from the photon pov. Light speed is causality speed so as instantaneous as you can get. Not from outside inertial frame however (they appear to move lightspeed).
Move interactions are physical interactions with another inertial frame so appear to obey causality.
This experiment is NOT it is the photon's information being changed, its knowledge and not a material process. It must some how know its own wave function, or pilot wave as an informational omniscient thing...
Thanks so much for these videos!
Fantastic soundtrack, and great animations. I particularly like the cat looking very inquisitively at the little puffs of wave.
+Dion Silverman, glad you liked my video.
This video scares me. What in the world in going on at the Quantum level?
sounds like just like a videogame, things aren't rendered if there are no players around.
okay, so it's not so much that the information is observed by a conscious mind, because the wave pattern drops when a detector is turned on regardless of whether a human being ever looks at the result of a detector. Instead, what collapses the wave function is if the information is simply available to the universe by way of entangled particles that can only behave a particular way as a particle if its "partner" is behaving in a particular way as a particle.
Then again, maybe the system collapses if observed by the detector, despite the fact that the detector is not conscious.
In any case, it seems that human observation is not what collapses the function if simply turning on a detector without looking at the detector result causes humans to observe the no interference pattern on the screen.
THIS. thank you. quantum mysticism gets on my tits and this business about consciousness needs stopping. 'observe' ah its a word, a different definition here, totally. following on from the uncertainty principle which talks about observation, how do you observe without interfering when the particle you use is equal in importance to things being observed and cant be divided. (although technically this experiment isnt uncertainty priciple, its observer effect, similar things really)
@boi detectors dont know anything because they are detectors not people. i dont quite understand the point you are making. a ball doesnt 'know' which angle to bounce, it just does it, its not that different.
YES
Eugene, your animations are great. I especially love the videos with cats.
Geoff Mulberry Thanks. I am glad that you like my animations, and that you like the cats.
Eugene Sir, what is the name of the music in the starting? it perfectly blended with your beautiful presentation
All the music in this video is from the free TH-cam audio library, and the names of the songs are the following.
Stale Mate
William_Tell_Overture_by_Rossini
1812_Overture_by_Tchaikosvky
Thank you so much. The animation really helps. Quantastic!
+Deacon Verter, glad you liked it. Thanks.
especially that cat, this video would be pointless without it.
Quantum physics is so crazy! Very good video.
jmanc3 Thanks for the compliment about the video.
This channel is simply the best for me. A lot of channels illustrate complex concepts like this one, with fancier animations but for inexplicable reasons, this makes actual intellectual undestanding simpler for me. Thanks for the good work!
Thanks!
The pause between important information, as well as the 3D cat, helped more to understand this very difficult topic. Big thanks to the animator for making things basic!
Thanks.
@@EugeneKhutoryansky 7 year old video, and a reply within minutes!? 😊 I wasn't prepared for that!
This is a tough one. Will rewatch.
14:32 So this means that there is a difference between a conscious observer like us and and an unconscious observer like the detector? That question is on my mind for quite some time now, does the universe differentiate between consciousness and "non-consciousness" ? Wouldn't that mean that without consciousness there cannot be a definite reality?
Hmmm this was probably asked by so many people, what do you think of this?
edit: okay i just finished the video, should have waited to ask that question since it is mentioned at the end :D hopefully you will adress this kind of stuff in the future videos
niv skillsurf Whether or not consciousness makes a difference is a matter of debate. There are a number of different philosophical interpretations of Quantum Mechanics. One of them states that a wave-function collapses when it is observed by a conscious observer. The other interpretations have a different explanation. And yes, as you said, I plan to eventually make a video that addresses the different philosophical interpretations.
There is no reason to assume Consciousness has anything to do with it when you entanglement I don't think. You could just say we only see the wave function we entangle with
niv Gnasherus The detectors aren't doing reading. The detectors have to be read by a recording device. Once that happens, the quantum wave collapses. In the real Delayed Choice Quantum Eraser experiment photons are hitting the screen or the detectors at a rate too fast for humans to decide whether or not to read a detector. Fast processors are implementing software to record no not record through which slit the entangled photon and it's entangled partner that hit the screen earlier in time. We can only play back the recording and match entangled particles. From the recording, we see that when it is known through which slit a photon passes, the photon hitting the screen acts like a particle. From the recording, we see that when it is not known through which slit a photon passes, the photon hitting the screen acts like a wave. There is no human consciousness involved. Quantum entanglement appears to break distance and convey information faster than the speed of light, instantaneously. Quantum entanglement appears to break time and convey information backward in time. Three years after this video,I have seen no papers that can satisfactorily tidy up this mess. A decision in the present causes an outcome in the past. 😖😖😖😖😖
@@khaledyasser8293 We do have a reason to assume consciousness is at play because the primary variable in this experiment is knowledge of how its set up.
Very great video!! I just loved your explanations, you've helped me a lot!
Please keep these videos coming!!
Theenerd ジェームズ Thanks again for the compliment. I am glad that you love my explanations, and that they are helpful. And yes, lots more videos are on their way.
great explanation, very insightful, good work as always!
Anon Ymous Thanks for the compliment. I am glad you liked it.
I really enjoy your videos. I would like to just make a comment about the music selection though. I think it would be VERY impactful if you choose darker music. Much of the "happy" major songs seem to take away from the awe-inspiring effect your videos generally leave upon a person. I see you use music form the Audio Library of TH-cam. If you choose more music from the Dark category (Classical and Ambient are usually the best of the dark genre), music more abstract and maybe even a little disturbing, I think you could greatly enhance the quality of your videos and add a uniqueness factor to your videos (All of the commercial industry already uses happy ukulele songs, you should avoid doing that). If you add this dimension to your videos (haunting music with awe-inspiring physics revelations), I believe you could gain a cult following. I with you the best with your channel and I hope you consider my suggestion.
Hey Daniel. I really enjoy the background music to be honest. I was wondering where is he taking it from. Do you know? Thanks in advance mate!
music is william tell overature, the lone ranger bit is at the end.
That cat gives me nightmares.
I'm so glad this video talks about the very fundamental concepts and I think this is the only one I've seen so far which has explained "What erasing of information means", I've been quite confused about it in the other videos which just seem to mention it without really explaining clearly. Thank you!
Thanks.
Thanks, Eugene, another fabulous video--and I'll be re-watching this one more than a few times. Some videos on physics feature narrators who talk really fast--possibly to sufficiently engage attention. I love it that your narrator talks at a normal pace with lots of pauses and sometimes repetitions to allow me to absorb the ideas. Your music and animations do the engaging. And, of course, the animations often help with visualizing. This is a brilliant and unique approach. I wish other video makers understood this.
+Alexandra Hopkins, thanks for the compliment. I am glad that you like the video, and the pace of the narrations. And thanks for the compliments on the animations.
+Alexandra Hopkins -- the fast ones that I despise, are the ones where they finish the video and then edit out the small pauses between sentences/paragraphs. Thus it becomes just one endless no pause nightmare.
Ha! Schrodenger's cat's person.
Here is the problem. To be an observer one must be conscious. But, we don't know what consciousness is so we don't know what an observer is either. Since we don't know what consciousness is we can't say for certain that that the particles themselves are not conscious. If the particles are conscious, they may change the way the mind perceives the patterns they make.
+CurbsideJimmy Haha lol. Everything is alive and watching you. They are keeping tabs on what you do whether you like/know it or not. c:
Curbside Jimmy No, an observer can be an nonconscious thing such as polarisation glasses
Steve Bergman
How so? It seems to me one of two possible things happen in this scenario
1 - Consciousness - meaning the awareness that some event has taken place - causes the "rest" of the event to also materialize, in the sense that if a particle is measured at a given point, it must have traversed through a certain path to get there, or
2 - All the events have been laid out in advance as an infinite set of possibilities, and when observation - or just the mere fact that an event has taken place - "forces" the event into existence in its entirety. That, however, would imply that time is only a dimension we travel through, and everything that ever was or will be was "created" instantaneously before even the first ever event to take place in our universe.
Seems to me like both scenarios imply the existence of consciousness, either within or outside the system. In the first scenario, the universe would be the consciousness I'm referring to. In the second scenario, an outside consciousness would have "created" the entire set of possibilities and then set it in motion.
What am I missing?
nice video, I am excitedly looking forward to your video about the interpretations of the experiments! best regards
Hans HansHans Thanks, and I am glad to hear that you are looking forward to my video on the different interpretations on Quantum Mechanics.
This is a great video. nice explanation, and WEIRD stuff!
First of all I would like to say that I think your videos are absolutely fantastic.
Except the two about quantum mechanics. You really make it seem like consiousness has some important role in the double slit experiment, which is definitely not the consensus by physicists. Im not sure if you really believe that or if it is a mistake by my part from interpreting the video, but you unfortunately make it look like it (a lot of youtube videos do) for example when the cat is closing its eyes and the results change. "Observing" in quantum mechanics does not mean "consious beeing observing". I believe interfere or disturb is a better word to avoid confusion.
Andreas Henriksson I also thought that consiousness had nothing to do with it, but how can it then be that the wave function does not collapse by measuring, but only by the information that the measurement produces? (As shown by the use of a quantum eraser) Khutoryanski already promised a video about the phylosophical concequences of this.
Andreas Henriksson There are a number of different philosophical interpretations of Quantum Mechanics. One of them is, in fact, the idea that the wave function collapses only when a conscious observer observes it. There are also many other interpretations of Quantum Mechanics, where consciousness does not play a role. However, all these other interpretations have to explain why the data makes it seem as if consciousness is involved. In my videos on Quantum Mechanics, I leave this as an open question, and I only state that it "seems" as if consciousness plays a role. I never explicitly state whether it does or doesn't, as this is a matter of debate, and no on really knows for sure when or how the wave-function collapses.
Eugene Khutoryansky Yes, there is a number of different philosophical interpretations of Quantum Mechanics, and one of the more unpopular (by physicist) and silly ideas is the idea that consciousness plays a role - an idea often used by new-age people and such who misuse Quantum mechanics to fit their own view.
What counts as consciousness? can a toddler collapse the wave function, a chimpanzee? dog? insects? This obviously creates some ridiculous problems (and its actually quite arrogant to believe that we humans possess a special ability to collapse the wavefunction..)
And I do not agree that the data seems as consciousness has something to do with it, just that your explanation of the problem make it look that way ;)
As a matter of fact I have never heard of any physicists that believe in this interpretation (Im a physics student, and have asked my professors about this)
I know you never explicitly stated anything, but you sure emphasized this very disfavored interpretation.
Andreas Henriksson All I am doing is leaving open the possibility that consciousness plays a role, without stating whether it does or doesn't, as there is presently no way to prove this one way or the other. Also, I think that the percentage of physicists who think that consciousness plays a role might actually be higher than you think, though they would disagree with each other over what counts as consciousness. In any case, the biggest issue I see for the view that consciousness plays a role is the question of what the Universe was doing before there were conscious observers in it, such as before any planets had yet formed in the Universe to support life.
Andreas Henriksson You are not considering that, maybe, consciousness has something to do. I am not by far instructed at quantum mechanics but using the logic that my knowledge in programming has granted me I can take a shot at it. This is that maybe our "consciousness" is like a system that kind of constructs a solid experience through the possible quantum outcomes so we can actually be self aware of our existence. I mean if you try really hard to think what consciousness is you will realize that it is way beyond understanding; it is like trying to see the back of your head in a place with no reflective surfaces. So what I'm trying to say is that maybe the Universe, time, space, and all energy and particles make no sense and are not correlated at all but our consciousness (which I think might be created by the way the particles in our brains are set up) is so complex that can make everything make sense among the quantum chaos and make us feel, well, conscious.
Any talk of the content of human consciousness being the deciding factor of whether or not "reality" is real is obvious nonsense! There is something fundamental that we have not understood
why?
Here is my opinion.
I don't think human consciousness is the deciding factor, but the fact that the information of the experiment exists somewhere in the universe. It can be registered on a sheet of paper, a hard drive or a brain. It looks like we are also entangled with the whole experiment.
I agree. It's very suspicious that this experiment is so accepted among prominent thinkers.
The blind jump from physics to philosophy is obscene. Physics has something to gain as does philosophy. Very politicized.
I have sen this experiment described in a different way and I am wondering if it has been done in this way.
Particle detectors are put on each slit. The date from the particle detectors goes into a computer and no one sees them until later. Photographic plates are used. The experiment is run multiple times with the particle detectors turned on each time. The plates are developed and fixed. Nobody looks at the plates until two weeks after the experiment. A that time no one has seen either the plates or the results in the computer. Now the computer randomly picks half the experiments and erases the results.
When the data is looked at the results for each experiment that had the detector data erased shows an interference pattern on the plates and the ones for which the particle detector data was kept show the pattern of individual particles.
Has this experiment ever been done? Could it be done?
I love this cat and your videos!! So good!
The more I watch his videos the more surprised I get. Love your work as always Eugene
Thanks!
This is one of the finest videos on this channel...😍😍😍😍
Mindblowing. Excellent video, as always
+AC Souza, thanks.
thank you for this amazing video !
bannajirocks You are welcome. Glad you liked it. Thanks.
Love how amaze science is!
Does the two slit experiment need to be done in a vacuum in case the air in the room interacts with the particle therefor theoretically you could figure out which slit the particle went through?
Or on a different scale, don't particles cause gravity so theoretically you can measure the particles gravitational wave effects somehow and determine which slit it went through? In that case you wouldn't really be affecting or touching the particle as it flies through the slit? I'm trying to think of a way you might theoretically detect something without actually disturbing it.
Thanks for these!
BigBad Wolfe You're Welcome!
Have you made the video for the different philosophical interpretations of this experiment yet?
In the delayed eraser double-slit experiment, if they have a video camera looking at the detector data, instead of the scientist, and the scientist erase the detector data before looking at it, will they see a diffraction pattern or a two lines on the screen? If they see the diffraction pattern and then look at the footage from the camera and then look at the screen again will it change to two lines? If they see two lines but decide to delete the video before watching it will it change to a diffraction pattern?
Just one question: Why is the blue striped pattern skewed to the left (yellow detector) and purple to the right (towards the green detector) instead of vice versa?
Thx for the video, you provided a easier way to understand this difficult and strange phenomenon
Barry D Glad to hear that my video made this phenomena easier to understand. Thanks.
What are the limitations of the quantum eraser?
Does it still restore the interference pattern if we endow the photons emitted by one crystal with another certain property (say, a specific polarisation)?
Is the result of that the same, if the four final detectors for the photons measure not only light, but also polarisation?
At 22:50, there are 2 cases out of 4 where we can tell form which hole particle passes. Here also we get interference pattern(as per video). what will happen if we go on increasing this possibility.like ,8 out of 10 ....or 98 out of 100 cases we know (which mean almost all the time we know).will there be interference pattern ? or it will be dark two strips with light interference ?
What if you have the double slits and another column of double slit right behind that but spaced out differently, would that affect the pattern?
lovely video, and i have to say... fantastic music selection for the subject matter. lol it's perfect
Thanks for the compliment.
I really like the creepy cat please never abandon him and let him stay in your vids
What if when the electron passes through the cristal, it gets itself entangled with the photon that is emitted? So when the photon is measured, it "passes the information" instantly to the electron that created it, then the pattern instantly colapses to a wave-like pattern or a particle-like pattern (depending on whether the quantum eraser was activated or not), even though they have already passed through the detector, forming the four possible patterns that overlap (as shown in the video). Does it make any sense?
How does a detector in front of the slit detect the photon without altering its velocity? Doesn't that interaction necessarily affect the outcome?
In the actual experiment, i I believe the detectors aren't actually making contact with the particles, not sure
I looked at myself in the mirror and my spin collapsed to be up. Incredible!
can we alter the path such that the path is known once it has been been determined that pattern is interference formed by wave........suppose we have decided to activate the quantum eraser and we observe striped pattern but the entangled pair of the particles, or photons emitted via detector still has to reach the photon detector........now by observing the results it can be known that the path that will be taken by photons would make it impossible to determine which hole it passes......suppose if i elongate the path significantly which then allows me to rig the experiment........say a step deactivating or nullifying the results of an eraser making the path determinable? Can we rig the experiment once we have obtained the stripped pattern result??
Does the Quantum Eraser is just another probability, of the 4 detectors, Of the 1/2 of the two holes and to the same of the beam splitters?
So what happens if one looks at the cloth to notice two xor more stripes, and then activates the quantum eraser (agreed beforehand to be executed several light-seconds away)?
Is it possible to get the striped pattern inside a computer simulation?
What´s the reason for the two striped patterns being offset from each other when the eraser is active?
what is the link to the video about the last question pls.
I don't understand about there being two offset possibilities of a striped wave interference pattern. How is that the two different offset patterns can emerge? Have I missed something?
Also, does this mean that if we shoot many particles through the slits without the detectors present, it will always eventually add up to a non-interference pattern because the two offset patterns will combine to that? I don't think that's the case as when I used a laser light to shine through multiple slits there was always an interference pattern. So what's that about?
Which delayed choice quantum eraser experiment are you exactly referring to in the video?
I love your channel
Glad to hear that. Thanks.