I'm a janitor. The toilets in the first floor restroom where I work need to be flushed twice. So I used the principles of retro-causality to make sure it happens. It's effect before cause. I put a sticker that reads "Thank you for flushing twice." Stating what hasn't happened yet as though it has, thus causing it to happen.
@javier.alvarez764
3 ай бұрын
Sounds like a self fulfilling prophecy. It happened because the observer followed the path to make it happen, if he didn't then it wouldn't have happen at all. That's good example though.
@xrp589baby
2 ай бұрын
exaaaaaactly
@LordOfThePancakes
Ай бұрын
But that doesn’t guarantee they will get flushed twice. The only thing you could potentially prove is that the probability of them getting flushed twice increases. But that’s only when looking at multiple points of data. You would need that in order to mathematically conclude an increase in probability. A single instance of whether or not the 1st floor toilet was flushed twice or not, from you putting the sticker thanking the individual for flushing twice, would only give you a single outcome, thus negativity any probability, or in the quantum experiment case, a wave pattern. just like you would get a single pattern when measuring a single electron particle in the double slit experiment. So you’re back to square one buddy. Sorry.
@artemiseritu
26 күн бұрын
That's what you think. In reality, nobody even looks at the stickers, but you think they're flushing twice because the sticker is there.
@QuantenMagier
11 ай бұрын
I think you totally missed the point here. The important part, is that the chosen subsets on detector 1 corresponding to detector 2 or 3 do not show interference, while the subsets corresponding to detector 4 or 5 do show interference on detector 1. This means the selected photons on detector 1 show interference depending on which path they took in the future.
@lex.cordis2
3 ай бұрын
These "debunkers" are brilliant at dismissing key aspects of the experiment. Also, it has nothing to do with time. The point is... there never was a photon or anything in the apparatus at any point until the end. What went through the apparatus was nothing more than a "probability wave."
@olejnikster
2 ай бұрын
Or energy is everywhere first in a set amount like liquid to its mean. But when added to aparatus it then goes into that said as SAME begining and end. But watch the wrap of the wave to have another beginning and end, and viola it interferes with the WHOLE energy subset. Weird, but logical weird. Is maybe energy "alive" in a perplexed way.is watching a capture of the the miniscule short time "living particle".@@lex.cordis2
@endycaceres7327
2 ай бұрын
@@lex.cordis2 that probability wave was collapsed once it went through the BBO crystal . They are in fact particles by the time they hit the detector.
@kurtrawicz1455
27 күн бұрын
@@endycaceres7327 in this case there shouldn't have been an interference pattern at D4 or D5, which is not the case. So there are two options: either electrons "relapse" back into probability function after some time (which looks more probable for the restricted view on the matter that I have now) or they don't collapse at the crystal at the first place. Also, the OP is right, all things said, it looks very much like electrons still predict the longer path in advance, or we both missed the point, in which case the point is not clear at all.
@VictorDiaz97
Жыл бұрын
Arvin is awesome! He admits his mistakes because he genuinely wants to learn and genuinely wants to teach as well. Some people let their egos get in the way. Thanks for the clarification, Arvin! 🌌🌠
@VicMikesvideodiary
Жыл бұрын
Agree!
@daveogfans413
Жыл бұрын
Problem is that society kinda punishes those who admit a mistake (sign of weakness/incompetence) and hold people with overinflated egos in high regard. Luckily the scientific community is different.
@Razor-pw1xn
Жыл бұрын
@@daveogfans413I don't think the scientific community is any different. It would be necessary to see what made him change his mind or by who or who he was convinced. Because honestly, if one reviews the video's claims seriously, they don't hold up.
@squarerootof2
Жыл бұрын
Nah, he's a crackpot.
@daveogfans413
Жыл бұрын
@@Razor-pw1xn So... What is the point? What is disputed? What doesn't convince u? It's unclear what disagreement u have.
@carlosmartinezbadia2532
Жыл бұрын
So many basic errors here...🤦♀️ To start with, what causes the photon to behave like a particle is NOT its interaction with a detector, as if the energy exchange between them broke the photon's wave 'form' : the wave also collapses a) without the photon itself interacting at all with a detector but when its entangled photon interacts with a detector, as happens in this experiment. B) it is also possible to make the wave function collapse and then reconstruct it precisely by manipulating the photon: first change the polarisation of the photon thus making its path distinguishable from the other and the wave collapses; then change the polarisation again down the line, the two paths become indistinguishable again and the wave reappears. That is, the wave is not "broken" by the interaction with a macroscopic element, otherwise you would't be able to reconstruct it with further interaction. Second: by being entangled, the two photons do not just start behaving like particles "because they have become localised". Each entangled photon, as the experiment shows, keeps splitting and recombining and creating interference patterns. The different distances between the slits and detector 1 and between the slits and detectors 2 and 3 have nothing to do at all with their not showing interference patterns. This just happens because D2 and D3 give away which way their twins in D1 went. The fact that the distance from the slits to D2 and D3 is longer than from slits to D1 just seems to prove that this giving away happens AFTER their twins have already hit D1without interfering with each other, and therefore, apparently, they have retroactively forced their twins to choose passing through one slit rather than passing through both. When, on the other hand their which-way info about the slits is not later leaked by their twin photons at D2 and D3 but erased by the latter's recombination before detection at D4 and D5, the photons at D1 behavED like waves at the slits and interferED at D1. That is, the giving away or hiding the which-way information of what happenED at the slits is apparently BOTH the result and the cause of that happened there! And I say there really ARE interference and non-interference patterns at D1 because there's nothing arbitrary in discriminating the pairs of detections that correspond to each other: each pair reveals a different story that really happened at a different time, of two entangled photons, one of which determines (apparently a posteriori) the past trajectory of the other. The interference patters at detectors D4 and D5 is not made up by the experimenters and correspond to detections of their twin photons at D1 at the same time (at our scale, for D1 should light up infinitesimally earlier than the other detectors, as it's closer to the slits) .Then the different pairs of detections are put in 4 sets, each corresponding to the 4 different trajectories of the entangled pairs: all the D1+ D2, all the D1 + D3, all the D1 + D4 and all the D1+ D5. Thus the interference or non-interferece patterns are revealed: revealed, not made up by cherry-picking, for, again, these four sets of detections, do correspond to four different pairs of trajectories that did take place independently from the others and need to be considered separately. Of course if you put them all together you get just a blob: for the same reason that all cats are grey in the dark. I'm not saying that this experiment proves retrocausality, but if not, something equally weird must happen. Dimissing it as the banal result of the confusion of the scientists that created it (and the ones who peer-revewied it) just reveals misunderstanding it.
@nadersaeed
5 ай бұрын
The explanation clarified that there's no retro-causality involved. However, the explanation may suggest another unusual and counterintuitive idea: that the photons going to Detector 1 somehow "knew" which detector their entangled photons would land at, i.e. either (Detector 2 or 3) or (Detector 4 or 5) despite the random selector being present. 1. When the photon takes the shorter path to Detector 1, it registers on "Screen 1" first, regardless of where its entangled pair ends up (Detector 2 or 3) or (Detector 4 or 5). 2. If you then compare the subset of photons registered on "Screen 1" with the patterns on "Screen 4" or "Screen 5" and get an interference pattern, it implies that the photons heading to "Screen 1" "knew" whether to show "Interference pattern" or "No Interference pattern" in that subset of photons, before their entangled pairs even reached the random beam splitter! This implications are even more unsettling, you can't win against Quantum Mechanics.
@alphabetical6
14 күн бұрын
The d1 will always show the spreadout pattern. When it detected at d1 along with say d5... It still shows spread pattern at d1 while showing interference pattern at d5. A pair of entangled photon can show different results if one is known to come from which slit and the other is not known from which slit it came from
@sidgillespie5879
4 күн бұрын
Qbism solves all of it
@cosmic_gate476
Жыл бұрын
Kudos to whoever is animating these experiments 👏
@FASTFASTmusic
Жыл бұрын
Kudos to the sound designer too!
@rickring1396
Жыл бұрын
You’re welcome
@FASTFASTmusic
Жыл бұрын
@@rickring1396I imagine 8-10 minute laser table sounds was a fun day.
@nag0074
11 ай бұрын
@@rickring1396are you the one who animated these?
@rickring1396
11 ай бұрын
@@nag0074 No, I was just being polite
@antimatterhorn
Жыл бұрын
there's still some mystery in that selecting a subset of particles in D1 that went into D4 or D5 recovers an interference pattern, but selecting D2 or D3 particles from D1 does not. /that/ is the delayed choice, that particles that will eventually end up in D4 or D5 but haven't yet hit the recombiner still nevertheless make an interference pattern at D1 (if you select them out afterward). like most things having to do with entanglement, there's no useful data to glean at the time of the experiment, but looking back at the data from the future shows that the data was nevertheless encoded with something, albeit unreadable in the present. that is still in conflict with the copenhagen interpretation, but then so is everything because that interpretation hand-waves "probability collapse" in a way that violates every conservation law, simply to preserve some irreducible level of indeterminacy and to preserve free will, and it isn't fair to say "how this happens isn't well understood" because "how this happens" has no explanation whatsoever in the copenhagen interpretation.
@DylanRJohnston
Жыл бұрын
Exactly! This explanation doesn’t get rid of the retrocausality at all! The photon pattern on D1 is created before the the beam splitter either preserves or erases the path information. It doesn’t matter that it requires correlating the photons from the detectors afterwards. You could imagine a more sophisticated version of this experiment where instead of a probabilistic beam splitter you had an actual person making a choice.
@gizmodelacruz
Жыл бұрын
There was a reply here, which sadly was deleted. I was vested in the follow up, please anon repost. Thank you, and thank you @antimatterhorn for your insight!
@nickrr5234
Жыл бұрын
I also agree that this doesn't debunk the retrocausality. The fact the the patterns at 4 and 5 combine to apparently give no pattern is because there is interference (which is the important fact) but it's out of phase when you combine them.
@user-sl6gn1ss8p
Жыл бұрын
@CraigGidney has a video called "The non-quantum delayed choice eraser". He kinda whizzes by going back from the classical analogy to the quantum system (as he admits in a comment), but to me it helped a lot in getting a taste of what to look for. He has a follow-up video setting up a simple simulation of the quantum system as well.
@gcewing
Жыл бұрын
What D1 records is always a superposition of two interference patterns, regardless of what happens later at any of the other detectors. It's just that D4 and D5 give you the information needed to separate those patterns, whereas D2 and D3 don't.
@ernestuz
Жыл бұрын
Man, this video is great. The user correcting you and then you explaining it to us is Internet at is best.
@JDTradesFutures
Жыл бұрын
Hi Arvin, thanks for the updated explanation. I am still wondering about the retro causality question though. If the D1 photons can be parsed out from the record of their entanglement with D2, D3, D4 & D5, and the difference between D2/D3 and D4/D5 patterns is caused by the erasure of the "which way" information which happens after the first entangled photons have already reached D1, doesn't that imply retro-causality? To make my point, for any particular photon that has just landed on D1, it's entangled particle will later land on D2-D5. If it lands of D2 or D3, it will be a "blob" pattern on D1 after parsing but if it lands on D4 or D5, it can be parsed into a wave pattern, caused by a beam splitter that RANDOMLY lets particles through or reflects them. This random act happened after recording the photon at D1 but it's influence can be seen at D1. What am I missing that says this isn't retro-causality? Also, if I understand you correctly. you said that the BBO crystal causes the which way information of the photon to be known, so why are we still seeing wave patterns at D4 and D5? Does it return to a wave once the which way information is destroyed? That still doesn't explain the ability to parse the entangled D1 photons into waves without some retro-causality. Genuinely interest if you or anyone else can enlighten me..
@alexfan3816
Жыл бұрын
wondering the same. ignoring the BBO lens issue, how does d1's result look and how does manual seletion on d1 work? seems to me the video says d1's pattern remain unchanged and the researcher picked out the fraction of photons entangled to those reaching d4d5 by data post-processing?? or by some quantum effect?? if it is the latter case, it is still retro-causality. And the former case sounds completely pointless to do.
@TysonJensen
Жыл бұрын
1. If the photons really exist in the first place, and we presume our interpretation is "quantum mechanics is secretly wrong" as so many physicists have, then retro causality is implied. 2. In Copenhagen, photons and electrons and all that aren't actually real. Only final measurements. The final measurements will always be found to magically agree with prediction, and we shouldn't worry our tiny little brains about what "really" happened. 3. In pilot-wave theory, the pilot wave is already a wibbly-wobbly timey-wimey sort of thing so it sees no surprises here. 4. Many Worlds can't explain this result at all (as with so many of the more recent experiments) and is probably just incorrect. 5. The quantum decoherence model would not say that the detector 1 "measurement" happened first at all. Instead, quantum states don't collapse, but rather "decohere" as everything finally comes to a final state. So the final measurement of detector 1 doesn't really exist until all the other measurements finish the decoherence process.
@wiesawnykiel1348
Жыл бұрын
@JDTradesFutures In this version of the experiment, we will not obtain two interference patterns in (the D1-D4 and D1-D5 coincidence)! Interference is not caused by lack of knowledge about the photon's path. For this to happen, the photon must move in a superposition of both paths (i.e., as if moving "both at once") and both components interfere on BS. The interference depends on the amplitudes from both photon paths and the phase difference of their optical paths.
@burt591
Жыл бұрын
Yep I'm wondering the same too
@JDTradesFutures
Жыл бұрын
@wiesawnykiel1348 but the interference pattern on d1 related to the entangled photons from d4 and d5 happens before the entangled photons pass through the beam splitter that randomly assigns them to d4 or d5. You cannot parse the information from d4 and d5 to get an interference pattern on d1 with a linear time explanation. At least I can't understand how..
@dorktime4526
3 күн бұрын
I was looking for an expert explanation of this experiment for so long because I felt like the results were dumbed down or sensationalized and all I could find were blog posts, KZitem videos, and articles regurgitating the same basic stuff with no real details. Thank you for finally explaining what is actually happening, this was driving me nuts.
@talleyhoe846
Жыл бұрын
Arvin has a real talent for making explanations of the complex and complicated so readily accessible.
@srb00
Жыл бұрын
He also has no idea what he's talking about. He completely missed the point in this "explanation" of his.
@EJBert
Жыл бұрын
How so or is this just a drive by comment?@@srb00
@talleyhoe846
Жыл бұрын
@@srb00 What is the point you claim that he completely missed. I'm quite sure he is not the one who has no idea what he is talking about.
@srb00
Жыл бұрын
@@talleyhoe846 How do the photons from the subset of D1 know they LATER ON landed on D4 or D5? They need to know that in order for the subset to generate an interference pattern.
@talleyhoe846
Жыл бұрын
@@srb00Suggest you rewatch the video (from around 9 minutes on) where he provides a detailed explanation of how the relationship and interdependence of the D1/D4/D5 outputs are formed and constituted. He further explains that the confusion arises from treating an interpretation of the experiment founded on an arbitrary and incomplete sampling of outputs as reflecting the comprehensive sampling of outputs. The alleged retro-causation manifested in D1 vanishes once the result of the full suite of interactions is taken into account. If you consider his explanation is in error, then explain what specifically is the error, where does the error occur, what is the correct explanation and what is the science-based justification for this explanation.
@Beerbatter1962
Жыл бұрын
Very cool. The overlapping of the patterns to show how the subsets combine did it for me. Until then, I still hadn't grasped an understanding. But after the merge, it was so much more intuitive. Well done.
@Razor-pw1xn
Жыл бұрын
The overlaping pattern doesn't explain anything. This is also present in the original paper of the experiment. It is one of the effects in creating the photon pair in which the phase is shifted by 1/2. For this reason there is interference patter and interference "anti-patern" or if you prefer, 2 well-differentiated interference patterns, which when analyzing the total sum of all the impacts appear as if there were no interference pattern.
@craigtevis1241
Жыл бұрын
Razor is right. Go read Ash's link "Original 1998 paper by Kim et al:" Scroll to the bottom to see the results.
@jamesyoungquist6923
Жыл бұрын
Yeah, this doesn't help me understand the why. Yes, if you add up the energies across the detectors then you'll get the same values, that's at least plausible. But not why those particular patterns show up, from an infinite set of possibilities
@craigtevis1241
Жыл бұрын
@@jamesyoungquist6923 Why is always tricky with quantum physics. Ash is right that this experiment doesn't prove retrocausality. But if a detector shows which slit the photon went through the pattern on the D1 screen is that of a single slit. If not the pattern shows a wave went through both slits.
@Beerbatter1962
Жыл бұрын
The important thing to understand, which is what the purpose of the video is, is that the pattern at D1 (particles or waves) does not magically change depending on which other detector you choose to look at. The pattern at D1 due to ALL of the photons is ALWAYS a spread out pattern. Because the which way information is always known by D1. And this is where the importance of understanding entaglement and superposition comes in. Encoded whithin all the photons reaching D1 is all the other possibilities about which slit the photon went through. And because of entanglement, one can determine which set of photons within ALL the photons reaching D1 correlate with those reaching one of the other detectors. The screen at D1 doesn't magically change. They used the screen at D1 to show the SUBSET of photons that correlate with one of the other detectors. That subset will show as an interference pattern if it correlates with detectors D4 or D5, because in those photons, the which way info is lost due to recombination. Conversely, the subset of photons displayed on the D1 screen will show a spread out pattern (wave function collapsed) for those photons correlated with detectors D2 and D3, because in those detectors, the which way info is still known. What I think this experiment really shows is the amazing phenomenon of entanglement, and due to it, you can instantly deduce information about an entagled partner, even though those two particles are separated by ANY distance.
@colintidwell8902
Жыл бұрын
Wow, this is a fantastic video. I’ve never seen this explain so clearly and succinctly. I love the de-mystification of quantum mechanics. It’s cool and interesting enough, no need to make it sound like magic. Thank you Arvin.
@VikingTeddy
Жыл бұрын
One of the worst offenders has imo been using the word "measure" when explaining to non scientist. I mean sure we measure the particle, but maybe we should go with something like "disturb", "collide", or even "poke". Then it wouldn't invoke the classical meaning of the word. A huge amount of woo comes from misunderstanding the word.
@cmddcd
Жыл бұрын
Wrong !!!
@VikingTeddy
Жыл бұрын
@@cmddcd What a thoughtful response, I'll have to chew on that for a while.
@colintidwell8902
Жыл бұрын
@@VikingTeddy yeah that’s a great point.
@steveunderhill5935
Жыл бұрын
Video gets real at 14:10
@TheMrDarius
Жыл бұрын
That’s a true teacher. Admitting where he was wrong and showing why and explaining what is now currently known. Yup new subscriber now.
@dysfunc121
10 ай бұрын
@anolakes Imagine being so bitter you can find issue with another thinking it's good to admit when you are wrong.
@kahlesjf
9 ай бұрын
He has more to lose as far as damage to his reputation and people second guessing past and future presentations if he does not correct his mistake ASAP. The comments below his original video include a challenge to his conclusion from someone with a Ph.D. in quantum optics. What is he going to do when he realizes that he made a mistake, just ignore it? Doesn't work that way in most of science. It is much more embarrassing to hang on to your mistake. He did not have to be so thorough in explaining his error, but he is a teacher with integrity.
@kahlesjf
9 ай бұрын
@anolakes Wherever it is you live, certainly there are politicians. Politicians do not only deny mistakes they know they have made, they create them intentionally. And yes, like actors and celebrities, they tend to be very insecure. Their jobs and livelihood depend on how they are perceived. You can pretend your circle only includes honest people, but the dishonest ones, especially politicians, affect your life whether you include them or not.
@kahlesjf
9 ай бұрын
@anolakes I also have an academic background with a Ph.D., now retired. Not sure why you are including me with your use of the phrase "you guys". In my comment above the one directed to you, I stated: "What is he going to do when he realizes that he made a mistake, just ignore it? Doesn't work that way in most of science. It is much more embarrassing to hang on to your mistake." I did not read your original comment carefully enough. But academics also emphasizes clear communication. To say you are sorry for "the world" someone lives in is a pretty broad category and despite your last sentence, it was not previously clear that you meant "one's circles". Also, your reply to the OP was flip, arrogant, and demeaning as far as assuming his comment was a reflection on "the world (he) lives in" i.e., "his circle" (a very vague term, especially considering it was intended to clarify the original).
@johnmagnotta8401
9 ай бұрын
With ALL science.. I don't believe it was a right/wrong situation. Science is ever flowing and nothing is right until it's proven wrong (yes, I meant to be wrong) we thought the earth was flat.. and until we showed it to be globular, it was for all intents and purposes - flat. The original scientists made a claim, devised an experiment that backed it up.. along comes many decades and improvements in measurements and voila.. its updated
@robertbutsch1802
Жыл бұрын
The text from the original paper hilighted in the video simply says that the authors have shown that which path information (represented by idler quanta) for quanta passing through a two slit apparatus can be erased after those quanta’s signal quanta have been recorded. This is in fact what the experiment shows. The paper does not say anything about retro-causality. I think that part is embellishment added later by others.
@gregmorris2022
Жыл бұрын
I always thought it would make this topic easier to grasp if you could explain how the “detector” works.
@steveunderhill5935
Жыл бұрын
Or how you shoot one electron/photon. Or how do you know a wave pattern is not being created from polarization or ricochet? Or how you get a layer of gold one atom thin? Am I poking god again?
@jamesflames6987
Жыл бұрын
Wikipedia exists.
@dfsfsfdsaf6511
Жыл бұрын
I guess the detector that only detects and doesn't interfere does not exist. I've read they used polarisation filters which are quite different than the animations would suggest and obviously interact.
@gregmorris2022
Жыл бұрын
@@jamesflames6987 Thanks for self identifying as “that guy” in this video’s comments.
@jamesflames6987
Жыл бұрын
@@gregmorris2022 The concept of quantum erasure is hard to grasp. Making the video hours long by explaining lots of incidental details which are not hard to grasp with a single Google search would not make it easier to understand.
@joshprior3583
Жыл бұрын
How is this not retro causality? The position of the D1 photon reflects the fact that it's pair had an interaction with an apparatus that caused it to either have interference or not. The interaction that the pair photon experienced occurred AFTER the D1 photon was detected. If there were no retro causality, then shouldn't the D1 photon land in a different position than it's pair since it was detected before the pair photon experienced interference?
@burt591
Жыл бұрын
Yep I'm wondering the same too
@janosmadar8580
Жыл бұрын
The answer is very simple. One half of the diffraction pattern in D1 belongs to D4, the other half to D5. When the original photon - on a BBO crystal - splits into two pairs of enragled photons, the properties of the photon pairs determine each other. If the photon going towards D1 is incident at x1 location on D1 such that it belongs to the D4 case, then its pair is in full destructive interference towards D5 and a total constructive interference towards D4, so it can only incident on D4 (or D2/D3). If a photon going towards D1 is incident at a different x2 location than D1, then its pair will be in destructive interference with itself towards D4 and can only arrive towards D5 (or D2/D3). The entanglement - and of course the right experimental setup - guarantees that HOW the photon arrives at D1 will determine whether the other photon can end up towards D4 or D5 (where there will be destructive / strengthening interference).
@zazugee
11 ай бұрын
@@janosmadar8580 I thin most misunderstood what restrocausality as future changing the past. But actually retro causality is same as reversibility of time in quantum interactions. Which means that causality works both forward and backward in time. The only issue with time symmetric causality is that decoherence break this retro causality and produce a loss of information that raise entropy.
@wiesawnykiel1348
11 ай бұрын
@@janosmadar8580 Everything is fine, but in THIS version of the experiment in D1 we will not see interference with D4 and D5. For this it is necessary - as in Kim's original version - for both paths of the passive photon to interfere on the BS.
@wiesawnykiel1348
11 ай бұрын
@@zazugee You understood correctly - retrocausality is the influence of future processes on past ones. However, there is no need - when making an interpretation - to use some vague concept of a "retroactive cause". The fact that QM equations are reversible does not mean that physical processes are also reversible. If you think otherwise, give an example of how you imagine backward causation in this experiment.
@garanceadrosehn9691
Жыл бұрын
This is a much cleaer explanation of all the parts of the experiment than I have seen anywhere else. Thanks for taking the time to explain and illustrate this.
@robbeverbeke
Жыл бұрын
But it's still "mysterious" to me how each photon from the relevant entangled pair "knows" how (i.e. in what pattern) it must hit the detector screen at D1. Because its entangled brother is at that point still en route to D2/3/4/5 and the photon at D1 strikes the screen before D2/3/4/5 is hit. Sure, you have to manually separate the patterns at D1 to make them match the patterns at D2/3/4/5, but the fact that they match is at all is weird enough, no?
@kevstuff100
Ай бұрын
The point of the video is that nothing changes at D1. What changes is what happens at D2/3/4/5 and this is after the events at D!.
@mickmccrory8534
9 ай бұрын
So.... If the lights come on, you will need to jump up & turn the switch on.
@PMX
Жыл бұрын
Sabine's video from a year ago made the same points, but it's good to see more videos like this were science youtubers question and clarify the "standard" explanations for quantum weirdness.
@dougaltolan3017
Жыл бұрын
I watched that one, couldn't understand it, had an inkling of what was really happening. Now here is my pat on the back for a right guess, but no gold star since I've not got any working out.
@tbardoni5065
Жыл бұрын
I believe what Sabine said was that its like a left and right hand glove or sock, which is what Einstein also said. Meaning that the pairs’ outcome was set and determined at the very beginning. But that is incorrect. She came to the correct conclusion, but how she got there was incorrect, is my understanding.
@Antifag1977
Жыл бұрын
Her channel should be "Sabine ruins...." She has a talent for contrariness and I love her for it lol
@sibbyeskie
Жыл бұрын
Oh quantum is still super weird don’t get too comfortable just because it doesn’t time travel.
@hemanthkumar5438
Жыл бұрын
She did refer to the quantum bomb experiment as more interesting
@NerdENerd
Жыл бұрын
I was kind of obsessed with this when PBS Spacetime first showed it. They part they leave out is that there is no interference pattern on the screen, there is only an interference pattern when correlating entangled pairs back to the screen.
@Posesso
Жыл бұрын
at least hey commented on Sabine's video admitting all the fault :)
@stuntmonkey00
Жыл бұрын
Matt did say that though... it was the answer to the challenge question for that series (if you could use this to communicate to your past self) he just didn't tie it together to say that there is no retrocasuality.
@saumitrachakravarty
Жыл бұрын
That is the most down-to-earth explanation of delayed choice as well as the original double slit experiment I have ever seen on KZitem. I wish I could give more than one like!
@shechshire
4 ай бұрын
I really like your explanation. Very well explained. Most people can’t explain this because they’re not good teachers. The interference pattern & slit pattern pictures at the end really puts everything together.
@0-by-1_Publishing_LLC
Жыл бұрын
I knew retro-causality was wrong before I even knew it!
@jimipet
Жыл бұрын
This is a better explanation of how the actual experiment was performed and what the results show, than the explanation in many other videos. However, this explanation, doesnt change anything about retrocausality. Retrocausality can still be the case here, if there is no other "better interpretation". Science asylum had an explanation how retrocausality cant be the case here. In his interpretation, it is very likely that the way that the first photons interact with the D1 screen, can influence the possibility that their counterpart will pass or not from the eraser, and all this leading to the interference pattern for those that pass the eraser. In that case, the past (photons hitting D1) is effecting the future (counterpart hitting the eraser) and not the opposite. And this makes much more sense, as the entaglement should be lost when the first photons hitting the D1. How the entaglement was lost, should then effect the counterparts photons path to either go through the eraser or not. It doesnt make much sense for the entaglement to still exist after first photon hitting D1.
@alka9scottus
Жыл бұрын
Spooky action nonetheless. “Retro-causation” at the photon to photon scale makes more sense imo. Would the photon at d1 then be randomly like a wave or practical? “Retro-causation” is an explanation that begins with the axiom that photon-wave-particle-double-slit-measurement is nonrandom, determined by measurement, whether explicitly the physical instrument or otherwise.
@alka9scottus
Жыл бұрын
So if that interpretation of the double slit experiment is valid, I don’t see how the photon at d1 could determine the later registry. “Can’t eat the cake and have it too”
@turbotong
Жыл бұрын
Is the double slit experiment done in a vaccum? Why doesn't every air molecule along the way that feels the photon act as a detector that collapses the wave?
@darrennew8211
Жыл бұрын
The photon isn't reacting with the air molecules. The quantum nature means the air molecule would have to absorb the entire photon, at which point nothing gets to the detectors and the sample is thrown out. (Or it doesn't get to one of the two detectors, and thus the one that did is thrown out.)
@TwilightMysts
11 күн бұрын
I find myself in the column of "This does not answer the question for me like you think it does." What I don't know is if that is because you see something I don't, or if I see something you don't.
@eriks8382
10 ай бұрын
“The devil is in the details” is a funny way of saying “oops I fucked up” lol
@neilboucher2529
Жыл бұрын
What more strange is that these things exist and happen in the first place
@KigenEkeson
Жыл бұрын
Sweet! Very clear explanation. We can all make mistakes, real men admit it and correct them. Thanks!
@robertbutsch1802
Жыл бұрын
This is the most lucid illustration of the DCQE that I have seen (I’ve seen some pretty bad ones). However, it still is a fact that the pattern recorded at Detector 1 is recorded BEFORE any of the subsequent goings-on even occur. You might say the Universe doesn’t have a clue what is going to happen later when the “blob” pattern at Detector 1 is recorded. Since which path information is available for ALL photons when the pattern at Detector 1 is recorded, we - according to the explanation of the normal two slit experiment when observations at the slits are made - expect that there is no interference pattern formed either “hidden” within the blob or not. It’s still difficult then to explain how the blob can be made to yield up interference patterns by manipulations that erase which path information later.
@gcewing
Жыл бұрын
I think it's important to understand that this experiment collects a lot more information from the detectors than the usual double slit experiment, which typically just has a screen or photographic film that munges all the photon detection events together. If you do that, then of course you can't extract any other patterns from it. But here, each individual photon landing on D1 is recorded separately, together with the position at which it was detected, allowing the possibility of correlating these events with other events happening elsewhere and elsewhen. I think it also means that the usual way of talking about the ordinary double-slit setup, that detecting which slit the photon went through "destroys" the interference, is overly simplistic. The interference is still there, it's just obscured in a way that makes it impossible to observe using a single detector.
@robertbutsch1802
Жыл бұрын
@@gcewing If the interference patterns are there at D1 ready to be recovered from the get-go even when which path information exists for all photons passing through the two slit apparatus, why did the investigators go to the trouble of later erasing that which path information for the photons used to reveal the interference patterns? In fact, there is no way to recover the interference patterns without erasing the which path information. The experiment is really a lot easier to understand conceptually than many people make it out to be. Erase the which path information, see the interference patterns.
@tomasprochazka1437
2 ай бұрын
Hands down the best explanation that does not play into the "weirdness" of QM. No black magic here just rationality. Thank you.
@mequavis
Жыл бұрын
this still does not remove retrocausality from functioning within a multiverse setup where the data doesn't come from the future but the present of an alternate timeline that is a possible version of our future. but speculative, I know. But I never thought retrocauslity functioned on a local level like the quantum eraser suggests, You have to factor in many worlds theory.
@Ped0P1gYOUTUBE
Жыл бұрын
More woowoo? There's no evidence for a multiverse. Many Worlds Interpretation is just a thought experiment. Stay away from those god awful marvel movies.
@mequavis
Жыл бұрын
closed thinking won't get us anywhere either@@Ped0P1gKZitem
@PortalUser2
Жыл бұрын
I think you get close to explaining it but there isn't enough information in your video for me to be convinced. If the position of an individual photon hitting the screen in detector 1 (with shorter distance) is associated with its entangled pair needing to hit detector 4 or 5 (with longer paths) that seems like a form of retro causality. I just don't think this can be explained simply without the math, but thanks for the attempt Arvin. It seems obvious that you get the sum of everything at detector 1 given the random effect of the splitters and you are shooting the photons 1 at a time.
@KeithCooper-Albuquerque
Жыл бұрын
I love your channel Arvin! It takes an adult to admit mistakes. Your doing so is a great example of how it's supposed to be done! Great job, my friend!
@steveunderhill5935
Жыл бұрын
Arvin’s channel has only gotten better over the years.
@phunkydroid
Жыл бұрын
Saying "I was wrong to agree with them before, here's now they are wrong" isn't really the same as saying "I was wrong". Especially since he's wrong in this video.
@sallylauper8222
Жыл бұрын
The wave bumps into the movie camera and turns into a particle causing everybody to have taken yoga classes in the distant past.
@Desertphile
Жыл бұрын
Thank you. "The Delayed Choice Quantum Eraser, Debunked" video by Sabine Hossenfelderis also good.
@srb00
Жыл бұрын
It is equally dumb and is not explaining the experiment either.
@willemesterhuyse2547
Жыл бұрын
Whether they select a subsample or not does not take away retro-causality.
@ThePinkus
Жыл бұрын
The point that takes it away is that the results in D1 are not affected by the (human or random) choice about sending the other photon in the "wavy" or "blobby" paths. The correlations that yields the two sets of partitions (one for the wavy choice, one for the blobby choice) of the results in D1 are considered after the choice. A hypothetical conditionalization ("collapse") on the choice of the path would leave the expectation for the results in D1 unchanged. Indeed, if we choose "blobby" we partition the results in D1 in the results D1|2 + D1|3 (the results of D1 that occur in the same run as the results in D2, respectively D3), and we have D1 = D1|2 + D1|3. And if we choose "wavy", we have the partition D1 = D1|4 + D1|5. There is no clue in the results in D1 about the choice, and the choice doesn't change, not even slightly, the results in D1. It is only that, for the given blobby/wavy choice, a given dot in D1 is more likely to occur with a detection in D2 rather than D3, or, respectively, with a detection in D4 rather than D5. Think of the Bell setup of the EPR, the choice about the direction on which to measure the spin here does not affect the results of the experiment there, it is when we collect the results that the correlations matter (the whole point of correlations). This is essentially an EPR with a time-like separation rather than a space-like separation.
@willemesterhuyse2547
Жыл бұрын
The results at D1 are affected by human choice: the entangled photon paired to the photon that will go to D4 or D5 shows interference in the past. The act of subtraction does not take this away.
@ThePinkus
Жыл бұрын
@@willemesterhuyse2547 That is not correct, there is no indication in the results in D1 that the other photon went to D4 or D5, and the latter doesn't make any result in D1 any more or any less likely. D1 doesn't show interference-like patters or blobs-like patters depending on the choice of the path. If we know that the other photon is going to be sent to D4 or D5 and not to D2 or D3, then we can say that D4 is more likely than D5, according to the position of the dot that we observe in D1. Do not mix the choice with the correlations after the choice. The point to make clear respect to the presentation at the end of the video is that it is not relevant that: D1 = D1|2 + D1|3 + D1|4 + D1|5, the partition of the results in D1 according to occurring in the same run as a detection in D2, etc. What is important is that: D1 = D1|2 + D1|3 , when we only apply this choice, and D1 = D1|4 + D1|5 , when we only apply this other choice. And the cumulation of the results in D1 looks exactly the same whatever the choice. Dots in D1 show no preference for their companion being sent the wavy or blobby path, or vice versa.
@willemesterhuyse2547
Жыл бұрын
@@ThePinkus I have read that it does produce an interference pattern if the entangled partner is later detected at D4 or D5: ask Poe. If it was otherwise there would be no issue.
@ThePinkus
Жыл бұрын
@@willemesterhuyse2547 the accumulated results in D1 do not change their shape because something happens or not to an entangled system, it is the point of no-communication theorems that are valid in QM. The fringes appear in the PARTITION of the accumulated results in D1, which remain in itself the same blob as it was before, according to the SELECTION of the runs that have a detection in D4 or, respectively, D5. This is a selection of the results in D1 that we do, it is not physical, after we collected the results from D1, D4 and D5 (in the intersection of the future cones of the 3 measurements) and is a selection that expresses properties of the COMBINATION of results, i.e., their correlations. These properties cannot be inferred, and are not physically indicated, from the results taken separately. We can write for the accumulated results R1 = R1|4 + R1|5. If we only know that the results in D1 are coincidences with D4 or D5, without knowing which of the two, we can make no partition of R1. Alternatively, we could collect data from D1, D2 and D3, and again have R1 = R1|2 + R1|3, as well as the same considerations. R1 doesn't change in either case, that is, R1|2 + R1|3 = R1 = R1|4 + R1|5. Again, whatever happens to the other photon, might it go the wavy or the blobby path or just continue to travel the Universe as long as it exists, or end up in a black hole, R1 keeps looking the same.
@LowellBoggs
Жыл бұрын
Arvin, thank you very much for this clarification. As a non scientist, I realize that simplifications have to be made for communication purposes and appreciate clarifications like this when people are clearly not getting the big picture items from the simplified explanation. However, I am left with this question : after the clarification, what Is the quantum eraser experiment telling us?
@Razor-pw1xn
Жыл бұрын
Although you have asked Arvin, I allow myself to doubt that the experiment is misinterpreted. The only scientific way to disprove this experiment is by using hidden variables or pilot waves, which lead to super-deterministic conclusions.
@MrMctastics
Жыл бұрын
@@Razor-pw1xnAre you familar with the mathematics?
@SKguy23
Жыл бұрын
Yes... like what was the purpose of the experiment ? After this clearance, does it imply that this experiment was basically of no use ?
@pinboru_
Жыл бұрын
I think this is a reasonable question. What do the results mean? It does seem like it doesn’t tell us anything.
@Razor-pw1xn
Жыл бұрын
@@SKguy23 Quite the contrary, Arvin's interpretation seems incorrect to me. I don't think the wave function in the crystal collapses.
@manabukun
Жыл бұрын
This still didn't clear my confusion. The individual entangled photons at separate detectors matching the detector pattern at D1, when selected as such, WAS the point of the retro-causality claim. Simply merging them together and claiming there is no discrepancy with the standard model does not explain it. The fact that when the concerned photons are identified individually, and compared to shorter paths, they DO show future states affecting the past. Either that, or our understanding of entanglement is wrong, which I have always suspected to begin with.
@shardator
11 ай бұрын
Yes, this is why it is called DELAYED CHOICE experiment.
@wiesawnykiel1348
11 ай бұрын
There is no influence of future states on past states. The position in D1 is related to the probability of detecting an entangled photon in D4 or D5 (if it has not been previously detected in D2 or D3). The order does not matter - whether it was D1, D4 or D5
@Quickshot0
11 ай бұрын
As I understood this explanation, what they are basically saying is... - We create a pattern of light, we'll call that D1 - Then we process quantum linked light in various ways, so that only part of those photons will still be visible. - We now unsurprisingly conclude that the remaining visible light can also be found back in the exact same position on the original pattern. And this remains true for all of the split off patterns of course. - If we put all the various different light back together, like it was in D1, then we get the D1 pattern again... unsurprisingly. If my understanding of the explanation is correct as such, all one is doing is basically eliminating parts of the light and making the extremely obvious discovery that the remaining light has the same position as it does in the first light spot. Because why would that change if you didn't shift the location?
@wiesawnykiel1348
11 ай бұрын
@@Quickshot0 The point is that in D1 we can obtain different patterns depending on what happens to the entangled photons "on the way" to the detectors D2, D3 or D4, D5. Although - such a small detail - in my opinion, in Ash's version, contrary to what everyone thinks, we will not see interference fringes (D1/D4 and D1/D5)
@Quickshot0
11 ай бұрын
@@wiesawnykiel1348 But is it really surprising to get the same patterns in D1 when what you're really doing is processing the light in different ways for D2-D5 which effectively block out parts of the light. And then after the fact when you remove the same parts of light in D1 would you not expect to find the exact same pattern? Of course this is based on my current understand of the explanation in this video. But on that basis I think you'd need an explanation for why the pattern found wouldn't be the same when you after the fact effectively manipulate the light in D1 the same way as in D2-D5. Because that would normally be exactly what you'd expect in such a case.
@francescocannistra7915
10 ай бұрын
What you say is only partially correct: indeed you can select subsets of dots on the screen arbitrarily in order to create whatever pattern you want. However, the subsets of dots that give rise to the interference pattern (as opposed to those that create a smoothed-out distribution) are not selected with the purpose of creating that pattern: it’s exactly the way around. In fact, the subsets of dots in D1 are grouped based on physical properties (photons with and without the which-path info), and only then it’s shown that from certain properties (photons with which-path info already resolved at the instant of the hit on D1) some patterns do emerge and from other properties (photons with which-path still unresolved at the instant of the hit on D1) other patterns emerge. It’s the coincidence counter in the experimental apparatus that makes the selection of the dots, grouping them based on what detector was hit by the entangled photons and thus distinguishing between dots originated by photons that have the which-path info and photons that don’t. Then it's just shown that an interference pattern emerges from the dots originated by photons without the which-path info. Therefore, the experiment really shows what is claimed by the authors: • The dots in D1 originated by photons that were subjected (just a bit later!) to a which-path measurement formed a smoothed-out distribution on the screen regardless of the fact that at the time they hit D1 they could still skip the which-path measurement. • The dots in D1 originated by photons that were not subjected (just a bit later!) to a which-path measurement formed an interference pattern on the screen regardless of the fact that at the time they hit D1 they could still undergo a which-path measurement. In other words, it's like if at the time they hit the D1 they had already incorporated in their dynamic properties the info on an event that indeed would have happened just a bit later (i.e. undergoing or not a measurement of the which-path info), What this means is indeed another story. On the other hand, since we know that space and time are so tightly bound and that non-locality is a core feature of QM, it seems to me this is just a manifestation of non-locality in spacetime rather than just in space. Then you can even call it retro-causality to let it fit better into the categories of our perception (and our classical mindsets) and indeed it looks like such a thing looking at it from the observatory of our intuition. Nonetheless, we know that such an observatory is flawed!
@ArvinAsh
Жыл бұрын
Let me try to clarify a question several of you asked. I apologize that I failed to address this in my video, as I did not realize that this would be a source of confusion. There is no retro causality. There in only a look-back at the positions of the subset of photons post-experiment. The positions of the D1 photons correspond to the D4 (or D5) photons because the photons are entangled, therefore correlated. So the fact that the patterns match should not be surprising. It’s to be expected due to the fact that we are looking at positions of entangled photons. They are expected to have complimentary positions. If you want a mathematical and more detailed explanation, physicist Sean Carroll, and friend of this channel, does a great job here: preposterousuniverse.com/blog/2019/09/21/the-notorious-delayed-choice-quantum-eraser
@lespoy445
Жыл бұрын
Yes it is already collapsed because of another detector is at D0 which is not mentioned in these discussions. The link you posted is then arguing the pattern interference is now separated by left and right spins into horizontal and vertical subsets. If I was to ask the person who wrote that article, to write their name on a piece of paper and then turn it around in front of a mirror, would they read the paper upside-down or back the front? It would depend on which whey they turned the paper, in a horizontal direction or a vertical one. So I question whether the slits were side by side or one on top of each other would yield a vertical pattern or a horizontal pattern, and is valid proof of that two different subsets are due to the spin of a collapsed waveform, but more an example of the orientation of the slits. The shift between D4 and D5 could be because they are a mirror versions of D1 and could be because D4 and D5 waveform interferes with D1. The only explanation I can fathom is that waveform and photons are not the same. If anything, the original two slits experiment is proof that a particle does not need to be tied to its wave function to move from point A B C and D and the photons are slowed by encountering contamination as the detector only appears to collapse the wave function, and are disassociated from the wave function, and this still agrees there is no retro-causality.
@lespoy445
Жыл бұрын
So the erasers maybe able to recombine a much-faster-than-photon wave function to D1 from D5 and D5 due to entanglement. Being a laser, the photons are in resonance with the waveform from any time. And is why the wave function can be recombined at D4 and D5 and show an interference pattern after D1 showed its interference pattern. This agrees with causality, and entanglement is with wave function in resonance, and not associated with individual photons.
@lespoy445
Жыл бұрын
Photons might only oscillate within the waveform. The waveform is not collapsed. Photons may be only be disassociated from the waveform peaks and pulled backwards down into the waveforms 0 point by the detectors electromagnetism that the photons induct..
@wiesawnykiel1348
Жыл бұрын
@Arvin Ash The truth is, I quote: "So, where the entangled pairs of the photons at D1 end up is not totally random(???). It corresponds to where they had landed on D1. So if anything, their position at D1 affects their position at any of the other detectors, not the other way around." In this version of the experiment, unfortunately, we will not see two complementary interference images (after the coincidence of entangled photons D1-D4 and D1-D5). Mere ignorance of the roads is not enough for interference to occur! Two paths (one from both BBOs) must be directed symmetrically to the beam splitter.
@wiesawnykiel1348
Жыл бұрын
It is not correct to interpret that: "But you have to remember that the wavefunctions of the photons at D1 have already been collapsed at the BBO crystal." Both photons would follow SINGLE paths, and interference would be impossible.
@kentef01
10 ай бұрын
I thought that the delayed choice in the double slit experiment was portrayed by simply move the detector from in front of the slits to very close to the screen. Then the particles/waves would pass through the slits undetected and interfere with themselves causing interference patterns until they get detected just in front of the screen by the detector. In theory they would still be spread out as an interference pattern, but they are not. Instead they appear to have traveled in a straight path without interference before being measured/detected, which would imply delayed choice. My point is, they always appear as particles on the screen, but where they appear as particles on the screen is determined by the interference that is caused on the way to the screen. If interference occur until the particle/wave is measured by the detector close to the screen they would still be spread out in a interference pattern, even if individual waves collapses into particles just in front of the screen. If this isn't true, I don't get what was so special with the slit experiment and delayed choice to begin with. :)
@Shmoolivich
7 ай бұрын
Your channel has become so invaluable to expanding my ability to conceptualize complex ideas of which I previously haven't been able to find comprehensive explanations for. Thank you for brilliantly articulating so many elements of science that have previously eluded my full understanding!
@leomuzzitube
Жыл бұрын
That does not change the mind-blowing fact that the entangled photon that ends in D1 "knows" if its pair will behave as a wave (if it lands in D4 or D5) or a particle (D2 and D3). So the argument of retro-causality persists. How can the photon that lands in D1 know ahead of time if its pair will land in D4/D5 or D2/D3 in order to behave as a particle or wave? I never thought the D1 screen was actually changing, but the core of the argument is that the photons that land in D1 do know if their pair will suffer interference or not, and that happens before the decision is made, if we assume the decision of going D4/5 or D2/3 is truly random. The fact that you need to extract subsets of the D1 screen does not eliminate retro-causality.
@kaczan3
Жыл бұрын
I still don't get it. It seems that there is still retro-causality with photons at D1 knowing if they should stay uncollapsed depending on whether the entangled partners end up in normal detectors or erasers.
@jeromebeck9781
Жыл бұрын
Same here, my understanding is that in this experiment, we are able to identify the photons on D1 that are entangled with the photons who end up on D4 for example, and if we pick up only those photons on D1, it does the interference pattern. In this case, isn't the measurement done on D1 affected by the path that the other entangled photon had, which is decided after the measurement on D1?
@alka9scottus
Жыл бұрын
The researchers can infer retro-causation at the small scale of particular entangled photons, yes. Some people must’ve thought that the D1 screen spontaneously changed entirely depending on which detector the “other” photon hit. At that obtuse scale - no retro-causation; the gestalt of the cluster does not change. But at the smallest noticeable scale here - yes retro-causation.
@alka9scottus
Жыл бұрын
(“retro-causation” being an interpretation of the effect)
@nickrr5234
Жыл бұрын
I agree. If you just look at photons hitting either 4 or 5, you get an interference pattern at 1 from their associated photons. If you look at photons hitting 2 or 3, then you get a blob at 1. So there is a correlation between whether the the photons hit 4 / 5 or 2 /3 and the whether an interference pattern is produced at 1. The fact that the patterns at 4 and 5 combined gives a blob is simply because the patterns are out of phase - it doesn't change the fact that they interfered while photons hitting 2 or 3 did not. In summary - this explanation doesn't make sense to me.
@ericlewisauthor
Жыл бұрын
This is my confusion as well. Is each measurement one pair of entangled photons? If you can assign a measurement as being clearly D1 and D4/5, then it's still valid, no matter if it's a subset of other measurements.
@j.anthonybattaglini6650
Жыл бұрын
This has been my favorite science channel for years! Such a good teacher
@c64cosmin
Жыл бұрын
When I saw this experiment presented the first time, my intuition told me that the path of the photon is predetermined before the photon is even emitted, pilot wave theory. This now adds more to that, whenever we do any quantum event, we are just subtracting part of the full probabilities. When the particle interacts with matter that is very determined then it inherits that and collapses to a simpler distribution, but when interacting with a material like a crystal that does "play" around with the photons in it's lattice, the inherited behavior is also inherited, which allow us to do amazing processes like crystallography, to determine the shape of molecules and proteins.
@maheshBasavaraju
Жыл бұрын
This is the best explanation for delayed double slit experiment with quantum eraser on the web. Period
@Josh-x3l
Жыл бұрын
Hi Arvin, I think am missing something in this explanation, and can use some help understanding where. Isn't the ability to extract those collapsed wave/wave interference patterns from the subsets of D2-5 in detector 1 the entire 'eraser' part of the experiment? The fact that it can draw those conclusions from entangled photons at an earlier interval is the question I am seeking to answer. I don't have a background in physics outside of personal interests, but have been looking for explanations of this experiment for years. The closest I have found to a complete answer is within the theories of Hugh Everett. I would also guess that similar lack of local 'realness' shown in Bell's inequality play a part too, but I don't know that anything directly connects them. I, too, am open to the idea of being completely wrong here, and would be extremely curious to know what I am missing in this video that my shed some light
@johnmalone5693
Жыл бұрын
An excellent clarification, thanks Arvin
@jagatiello6900
Жыл бұрын
Sabine made a vid on this a couple of years ago (tried to paste the url but YT erased the reply, I guess censorship is a far worse eraser than quantum)
@Razor-pw1xn
Жыл бұрын
@@jagatiello6900I fear that Arvin is also getting carried away with super determinism, which is the only way to scientifically refute the conclusions of this experiment.
@jagatiello6900
Жыл бұрын
@@Razor-pw1xn A satisfactory explanation of the measurement process may be the key...or may be not, who knows.
@Darthvanger
Жыл бұрын
I was confused seeing your 2019 video after Sabine's debunk video. Thanks for the update, it's now exactly as what Sabine said in her debunk video!
@abhishekgarg5286
Жыл бұрын
Good video, but just wanna mention that the experiment can indeed by effected by consciousness. The reason is that there is another experiment that I had heard about where the results of the measuring device (before the photons enter the slit) were deliberately thrown out, and that led to two lines showing up instead of an interference pattern, implying that just the "act of observation by a measuring device" did NOT collapse the wave function, but only the act of "reading the results of the observation collected by a measuring device" collapsed the wave function. What collapsed the wave function was - when the results of the measuring device were chosen to be "observed". If the person doing the experiment deliberately makes a conscious decision to not look at the results & not store the results anywhere & just throws away the observation, then the wave collapse does not happen, thereby implying that a "conscious observer" was the reason for collapse of the wave function, not just the act of measuring the data that collapsed it. Thus, consciousness did indeed effect the results. Let me elaborate on consciousness a bit, and how the collapse of the wave function leads to certainty of a result, whether as a particle or a wave pattern. Remember when we go to sleep and we are like in an "un-conscious" kind of state? And when we wake up, it seems real to be awake again? Well, that's what's happening with the collapse of the wave function. Before the wave function collapse, it's like a dream, anything is possible, there is no certainty on what is or isn't real. When the wave function collapses, that's when reality appears. That's the universe doing its dreaming, and when the wave function collapses, then the photons settle into a specific state of reality.
@Razor-pw1xn
Жыл бұрын
Reminds me of the simulation hypothesis. Can you give some more information about the experiment, paper, scheme, authors... I am interested in it. If not, is it a mere fantasy? Remember that the observer cannot change the result of an experiment once the wave function has already collapsed. And to observe is to collapse. It doesn't matter if a human, animal or thing does it. It is the phenomenon of decoherence.
@naswinger
Жыл бұрын
thank you for the clarification. that experiment is now much less cool though. 😅 with your explanation it's exactly what you would expect to happen on the other detectors.
@fritt_wastaken
11 ай бұрын
There's no confusion, it still implies retrocausality. Your correction doesn't change the essence of the experiment
@ZotVanBelgie-jn7oz
9 ай бұрын
" If you think you understand quantum mechanics, you don't understand quantum mechanics " I would change that to ... " If you think you understand quantum mechanics, then it's well explained by Arvin Ash "
@RAFAELSILVA-by6dy
Жыл бұрын
The single-slit pattern is usually overlooked in popular science videos. Any quantum particle diffracts when it passes thtough a sufficiently narrow slit. The whole concept of a particle "behaving like a particle" when it's observed is a misconception. If you have which way information on a particle in the double-slit, then it behaves exactly as it would behave if there were only that one slit. This includes the particle exhibiting the "wave-like" property of diffraction from the single slit. The "collapse" means that you no longer have a wave-function in the superposition of both slits, but a wavefunction that corresponds to a single slit.
@drbuckley1
Жыл бұрын
Really great, intuitive explanation. Thanks for debunking the cranks.
@pwinsider007
Жыл бұрын
Waves interact with particles of air then why doesn't there wavefunction becomes localised?
@DrDeuteron
Жыл бұрын
@@pwinsider007the interaction is coherent
@darrennew8211
Жыл бұрын
Given that the people who invented the experiment gave the retrocausality argument, I'd be hard-pressed to call them "cranks." Not everyone who is wrong is a crank.
@alka9scottus
Жыл бұрын
@@darrennew8211 Exactly. “Retro-causation” isn’t written on the D1 screen, but it seems like an accurate interpretation of the effect they studied.
@LuisAldamiz
Жыл бұрын
He's not "debunking" anything, just clarifying details he originally got wrong.
@hannesaltenfelder4302
Жыл бұрын
Things I googled during that video: Retrocausality is the mistaken(😄) idea that future events can influence past events, contrary to our usual understanding of causality and time. Decoherence refers to the process by which a quantum system's behavior becomes classical and loses its quantum properties due to interactions with its environment.
@kevstuff100
Ай бұрын
It should read "is the mistaken idea"
@lethalwolf7455
8 ай бұрын
The common misconception is in thinking of the detector as a camera, where in reality it’s more like a shotgun blast from the particle’s point of view. You can’t detect anything at this scale without interacting with it.
@watchguy7986
8 ай бұрын
Very interesting ! This could be the cause of the collapse and nothing supernatural. The more I learn about this the more I am finding out there are some EXTREMELY simplified explanations out there without the details your really need and should understand if you want to attempt to wrap your head around this
@augustadawber4378
8 ай бұрын
@@watchguy7986 Unfortunently, sub-atomic particles have to 'know' they have been collapsed. If they don't 'know' this and the self-aware Conscious Observer doesn't 'know' this, there is no collapse.
@JebJohnson-dg6yo
7 ай бұрын
One caveat- the wave function "localizes" to a single slit, but it does not collapse until it hits the detector. The wave function is simply updated to the wave function of a photon travelling through a single slit. Not sure if this was pointed out, but I thought it worth reiterating.
@naninano8813
Жыл бұрын
I think Sabine was first who pointed out how mundane results actually were and and then Matt from PBS SpaceTime commented that, yeah he also bought into woo a bit wen describing the experiment.
@Patiboke
Ай бұрын
I think what causes the weirdness in experiments like this is time dialation. The photon arrives at detector 1 first... for us, but not for the photon. The photon travels at light speed, with infinite time dialation, so for the photon everything happens simultaiously. Past, present and future are the same point in time.
@unheilbargut
9 ай бұрын
Thank you so much! I FINALLY understand it and it makes sense.
@punkypinko2965
Жыл бұрын
Thank you so much for the great explanation. I completely agree. It's funny how all this makes perfect sense to me, not that I understand the math of quantum mechanics, but this is the way I've thought about the double slit experiment for a while. If you just accept that the photon is a wave until it interacts with something else, like the detector or the screen, then it makes perfect sense.I remember many years ago people talking about human consciousness creating reality, man, that mumbo jumbo drove me crazy. I always knew there was a normal physical interaction to explain it.
@aa-jt1yt
Жыл бұрын
Yeah this new pseudoscience its getting to too many young minds like a plague. These happy go lucky new age theories drown out the real answers to the world most sought after questions like what is consciousness. Well when you go on ur own journey and research the neuroscience biochemistry philosophy of it all, u begin to realize the brain is just a biological computer taking in information and enriching it with qualities and emotions. The reality we experience, its a neurological simulation/ recreation of the outside world. Everything u think is outside the mind, when u look around, is actually within, such as colors. The eyes go to the brain, and never come out, ur perception of the world has to take place within the mind. Some examples are as follow. Theres no vivid blue or vivid color in any electromagnetic wavelengths. We detect a force and label the signal with a neurologically created color. Id love to go more in detail in explaining what in our experience is created by the brain and what actually exists outside, but its very abstract and philosophically challenging. But in all, consciousness is a mind phenomenon and the brain has no control over the outside world, but it does have access to how we see the outside world. And with that the brain can add to it, which it does. Consciousness is typically understood as the awareness of ones self. All the mind has to do is created a separate network for self identity ideas, and then it can experience them with the recreated world. Identity is like an illusion, it exists no where expect within the mind. Of course i cannot explain all of consciousness but i can confidently say it all takes place in the brain, and there should be no mysticism around it. With all the brain lesions that humanity have studied its safe to say every aspect of the human experience is localized to the brain, and without it the recreated world will no longer exist. Colors, emotion, memory, spatial awareness, etc all go away at death. So two birds with one rock, consciousness and afterlife; consciousness is another process within the brain added to our sense of reality. Is there an afterlife? When the brains no longer function neither will the perceived reality, there are cases of brains being in states between life and death, and releasing large quantities of neurotransmitters, which in turn effect reality, which may make u feel like ur leaving ur body or seeing white lights. Id assume the whole after life stuff was theorized by stories of hallucinations during near death expirerencs. Our world is pretty boring to be fair, but the brain is the painter to a very bland universe.
@wiesawnykiel1348
11 ай бұрын
Yet patterns, e.g. interference patterns, arise because we select information using complicated equipment. Without it, in D1 we only see a chaotic blur. Similarly, the patterns in D2 and D3 do not arise because a photon passes through one slit. Simply put, in 1/4 of the cases, the passive photon moving in the superposition of all paths lands, for example, in the D2 detector. A'posteriori physicists wrongly interpret that the photon has already chosen its path when passing through the slits. This is a similar error to the reasoning that the polarization of both entangled photons is determined at the moment they leave the BBO crystal.
@ebehdzikraa3855
9 ай бұрын
Arvin have his own agenda on every QM videos. Which is objective reality interpretation. Sadly, as other interpretation, this is not proven. Even, contradicting with actual observation. He always said that wave function will collapse because of particles interact with any type of things, not because of human measurement. But he forgot that, every particle beam, photon, electron, anything, will interact with anything once they are emitted. But didnt collapse their wave function. They only collapse when there is measurement
@wiesawnykiel1348
9 ай бұрын
@@ebehdzikraa3855 A "wave function" is a mathematical object used to calculate the probability of some phenomenon occurring, and like any such object, it does not "collapse". If a photon is absorbed by an electron, someone may assume that this is a phenomenon analogous to "measurement" - for example, recording a photon in a photomultiplier tube. However, it is forgotten that this entire process takes place in the observer's frame of reference, i.e. it "happens" from his point of view. It looks completely different in the world of quantum particles (e.g. "from the point of view" of a photon).
@scottlampe70
Жыл бұрын
Great video. The last couple of minutes you pulled it all together brilliantly. Nobody has ever mentioned that the sum of each pattern is the same as detector 1. We need more PhD's in quantum mechanics watching youtube to help us.
@joaquinferrazzi923
Жыл бұрын
why tho. ¿just so that us amateurs can go "oh that's interesting"? tbh, unless someone is studying this at university, the information is so complex that it's kinda useless to the layman. It's like wanting to understand derivation in maths without know much about multiplying, or without actually doing math ever. It's interesting information, but there is no real point to it if you don't trurly understand it
@scottlampe70
Жыл бұрын
@iridium8341 I'm 53 years old with a full time job and a family. There is no way I'm going to go and do a quantum mechanics course at university. However, I still find it very interesting. KZitemrs like Arvin help make the concepts understandable for people like myself. Phd's watching these gives an opportunity for corrections to be made in the information being delivered.
@scottlampe70
Жыл бұрын
@@joaquinferrazzi923 did you have trouble comprehending the information delivered in the video?
@ernestchadwell9069
Жыл бұрын
*_"goes straight through, almost as if it didn't notice the slit at all"_* Reminds me of a girl from my village, slack Suzie.
@Abstract-King
10 ай бұрын
Best retrocausal explanation till now
@icaleinns6233
Жыл бұрын
That is an EXCELLENT explanation! The original report gave me the funny feeling that something wasn't quite right because it seemed to violate causality, but I'm not trained enough to dive into the details like that. Hand picking the data makes perfect sense as the explanation. Just proves numbers can be tortured to make them say anything you want them to!
@stevenredmond4347
Жыл бұрын
Thats how the quantum bomb experiment makes you feel as well...except it is actually legit.
@UshiromiyaXyrius
9 ай бұрын
I remember Sabine explained exactly this in her old video. Thank you for explaining this in a simpler way and to correct the previous unintended confusion !!
@augustadawber4378
8 ай бұрын
In order for the Nature of the sub-atomic Particle to be known, all the results have to be obtained. In order for all the results to be obtained, both the sub-atomic particle and the observer has to 'know' what those results are. If the observer is not aware of all the results, how do we know if the nature of that sub-atomic was changed in the past or not ? If the observer is aware of all the results, how do we know the results are or are not from a particle being influenced in the Past ? As John Wheeler has postulated, wether a photon leaving a Star is a particle or a wave, depends on wether an observer from billions of years in the future observes it as a particle or a wave. Thats even though that particular Star still even exists when it is observed in the far far future.
@amarured
Ай бұрын
(Correct me if I'm wrong on this) But I think everything about this selection at 11:55 and the prior common misconception is actually pretty cool !! Because it once again reiterates how nothing is locally real but instead in superposition! But through interaction with all the matter (other particles, atoms, the whole measuring device etc.), the superposition gets so diluted that it turns into "classical behaving matter" (acts like single defined particles). Yet through the entangled particles then... if u single out the specific particle within the regular behaving "normal matter like" particle cluster: u again see the behavior of superposition and wavelike behavior! I think this is the coolest part of this whole experiment.
@bakshiavijit
Жыл бұрын
Despite the correction offered in this video, even if we pick up subset of data, it still is a mystery how it is that whenever there was a detection in D4 or D5, there was contribution to only the interference forming subset at D1? Why? And how is it that whenever there is detection detection in D3 or D2, there was contribution to only no-interference subset at D1? We could technically keep the beam splitters (BS, green triangles here) a light year away, in principle, then whenever photons are detected at detector D4 or D5 , we would know that 12 months ago a corresponding photon was part of a interference forming subset and not a non-interference subset. The mystery remains: what is it about entangled photons, that whenever a photon contributes to an interference forming collection at D1 (even though we can't tell yet if it was part of such interference forming subset) , it is guaranteed that A YEAR LATER the beam splitters will send the paired photon to D4 or D5 , and NOT to D2 or D3. How BS know? What is the correlation behavior that remains in the paired photon on its way to beam splitters light years away? The mystery remains.
@NorskInjustis
3 ай бұрын
so, it is NOT understood
@DeanHorak
Жыл бұрын
Excellent. Retro causality never made sense to me. QM tells us we must reject our intuition and just trust the maths. I’ve accepted that, but was never comfortable with it. This is just another example of how the interpretation of scientific results matters.
@abody499
Жыл бұрын
Yessir! Science _always_ comes laden with subjectivity.
@srb00
Жыл бұрын
The math is correct. This subject is way over Ash's head.
@DeanHorak
Жыл бұрын
@@srb00 , Right. The point being that the math is correct, but it doesn’t necessarily explain reality.
@irrelevant2235
5 ай бұрын
*Boy, You Are Wrong Again! (At least in your "fuzzy collection of dots" explanation)* I'm glad that you're able to clear up your illustration later in the video which shows a blob pattern instead of two individual clump patterns which is mistakenly and typically shown on most illustrations when a detector is placed at the slits. However, your explanation of this blob pattern is incorrect where you said at 7:20 _"the photons interact more with the slits, which causes the photons to spread out as a fuzzy collection of dots"_ . This blob pattern or "fuzzy collection of dots" as you put it is actually due to the wave function and not the individual photon particles. Your illustration suggests that once the photon leaves the detector as a particle, it continues to be a particle and then hits the backwall. This is incorrect. Once measurement has occurred by the detector, the wave function collapses at that single point of measurement where the photon is a particle at that point. However, the photon doesn't continue to be a particle after it has left the detector. Why would it since it's no longer being measured? Instead, the photon goes back to being a wave function after it has left the detector. Once the photon has left the detector where it's no longer being measured, it's no longer a particle and continues to be a wave function until it hits the backwall where it becomes a particle again. The pattern which you will see at the backwall is due to the wave function going through a single slit (either from slit A or slit B) which produces a diffraction pattern or blob pattern as I put it or "fuzzy collection of dots" as you put it. Physicist Sabine Hossenfelder gives a very good explanation of this in her "The Delayed Choice Quantum Eraser, Debunked" KZitem video.
@PhilMoskowitz
28 күн бұрын
I seriously think some people, including Arvin Ash, are misreading this experiment. Originally no one was talking about the past changing the present in regard to this experiment. That got started by people posting videos on KZitem and other social media jumping to the conclusion that the future was affecting the past.
@augustadawber4378
8 ай бұрын
Apparently the Photon 'knows' it is being measured. What happens if you remove the Measuring device after the results are in and then destroy the measuring device before anyone has a chance to see what the measuring device recorded. "In the future you are choosing a sub sample of the data you made in the past."
@nicholasuloth6530
Жыл бұрын
Well either the random choice the second particle makes is effecting the past behavior of the first particle at D1 or the first particle at D1 is determining the future path through the beam splitter which is no longer random and knows about the arrangement of the detectors D2..D5. Or the detectors themselves are colluding in their results. Its not clear which interpretation you are suggesting. Sounds like the retro causality is actually the simplest explanation.
@corneliuscorcoran9900
11 ай бұрын
Clearest and most comprehensible presentation of this experiment, I have ever seen....and I've seen a few.....Cue: thousand yard (914.4 m) stare.
@CleverNeologism
Жыл бұрын
I love the delayed choice quantum eraser, it's the next-level thing you have to make sense of after the original double-slit experiment. But, what if you had the detectors feed into qubits. By qubits I mean whatever data storage is necessary to maintain entanglement. What happens if you erase the qubits, then observe the screen? Can you force a "quantum amnesia"?
@augustadawber4378
8 ай бұрын
In order for the Nature of the sub-atomic Particle to be known, all the results have to be obtained. In order for all the results to be obtained, both the sub-atomic particle and the observer has to 'know' what those results are. If the observer is not aware of all the results, how do we know if the nature of that sub-atomic was changed in the past or not ? If the observer is aware of all the results, how do we know the results are or are not from a particle being influenced in the Past ? As John Wheeler has postulated, wether a photon leaving a Star is a particle or a wave, depends on wether an observer from billions of years in the future observes it as a particle or a wave. Thats even though that particular Star still even exists when it is observed in the far far future.
@DavidFMayerPhD
Жыл бұрын
The notion of duality is widely misunderstood. Although there is a "partnership" between wave and particle, the wave is the Senior Partner. The particle is an artifact of the measurement process and does NOT EXIST prior to measurement.
@csabakoos1650
Жыл бұрын
Measured by TIME
@DavidFMayerPhD
Жыл бұрын
@@csabakoos1650 ??? what do you mean???
@csabakoos1650
Жыл бұрын
@@DavidFMayerPhD Sorry for the late response. It is just a crazy idea. Here it goes. I belive that what we consider as space is actually time. Space is the origin and mechanics of time. No space no time. The flow or passage of time we are experiencing is due to new space being created continuously, without it time would stop. To support this claim there is, μ0 and ϵ0, virtual particles and dark energy. The present represents a specific relative configuration of matter and energy in a given moment in time regardless of reference frame. All different. The more mass the grater is the resistans to move in time. Dark matter could be some form of lagging in the passage of time, or time itself could be spread out a little bit in to the past and in to the future. It is the speed of time that gives rise to the speed of causality. The 3 main function of space. Enable thermodynamics, to slow down light and to keep time. SIM?
@DavidFMayerPhD
Жыл бұрын
@@csabakoos1650 WHAT?????
@MetroidChild
8 ай бұрын
All I got from this was that we really should look at trying to measure photons from the double slit experiment as losing sight of the ocean by staring at the waves, we only lose the interference pattern because we willingly discard the reference frame that allowed us to observe the phenomenon in the first place.
@ThePinkus
Жыл бұрын
One point that might be better emphasized to clarify the argument, and might help with some of the objections in the comments: at 14:20, the important point to make out is not just that, in one experiment where we have runs with different choices (human, mechanical, or random doesn't matter) for the correlated photon going the wavy or blobby path (self explanatory nomenclature, I hope?), we have that the results (or expectations, equivalently, as theory and experiment agree) of D1 partition according to: D1 = D1|2 + D1|3 + D1|4 + D1|5 where on the right we are listing the results in D1 that occurs in the same run as a detection in D2, D3, D4 or D5, respectively (apply perfect detection and perfect run separation assumptions). What, instead, makes the argument clearer is that, when we always choose the blobby paths: D1 = D1|2 + D1|3, when we always choose the wavy paths: D1 = D1|4 + D1|5, and D1 (accumulated results or expectations) is the same in both cases (the picture might be misleading!). A dot in D1 shows no sign of being wavy or blobby on its own, specifically there is no place where it can only occur, or it is even more or less likely to occur, if the wavy rather than the blobby path is chosen. When we observe a dot in D1, then we know that if we choose the wavy way for the other photon, then D4 is more or less likely than D5 depending on the dot position, and if we choose the blobby way, the same applies for D2 and D3. But the position of a dot anywhere in D1 doesn't make one choice any more likely than the other, nor the choice makes us update our expectations about where we expect the dot in D1 to have occurred, and accordingly the cumulated results in D1 show no sign of discriminating our choice. Do not mix the choice with the correlations that we consider afterward. Think of this as an EPR setup, with time-like separation instead of space-like separation. This is all about correlations, not causation. Correlations don't care about separation, the only requirement to observe them is collecting the results, which only occurs in the intersection of the future cones of all the events that determined the results. Thus there is not a big difference with a Bell setup for EPR. The choice of the direction on which to measure the spin here doesn't affect the measurements and results over there. Substitute, here and there with now and then, and we have the current experiment. Of course, what correlations we show once we collected the results depends on the choices, which is all the point of correlations and implies no causation.
@intheair1987
11 ай бұрын
Analogy: both of your hands painting with black paint. Your right hand drawing a flower. Your left hand painting the background black. = You did not paint anything. You selectively chose to isolate the result of either hands. When combined, it’s just a black piece of paper. You did not draw anything.
@ShinySephiroth1
Жыл бұрын
Homer: "Brilliant... I have absolutely no idea what's going on."
@marcdraco2189
Жыл бұрын
Kudos for admitting you're wrong. This is way over my head. I did a version of the double-slit experiment with a piece of very thin wire and a laser pointer for a cat. It's crude, but it works and my brain melted seeing it in real time!
@erinm9445
10 ай бұрын
Yes! I did it with my cat's laser pointer and three mechanical pencil leads! Could also use two of the leads to see the single slit interference, and how that looks different from the double slit interference! 🤯
@marcdraco2189
10 ай бұрын
Mind blown indeed!@@erinm9445 This is one of the few VERY cool quantum physics (probably the only one) that we can do at home.
@torencalduris3114
10 ай бұрын
Why not delete your previous, mistaken video? I appreciate the transparency in showing your mistakes, but some people will only watch the incorrect video. The goal is to educate, not misinform, right? Or is the goal maximum clicks?
@635574
9 ай бұрын
There are unwanted consequences of deleting or prrivating videos, but mostly becuasue you get more views when you link the correction on the olf videos page.
@strangevideos3048
9 ай бұрын
Scientists know NOTHING trust me .each of us can speculate and theorize 😉
@torencalduris3114
9 ай бұрын
@strangevideos3048 Maybe you're right, maybe you're wrong. I'm certainly not going to trust you, I don't even know you.. Lol But for arguments sake, if scientists know ONE thing, your argument fails. I do appreciate your zeal, though.
@strangevideos3048
9 ай бұрын
@@torencalduris3114 Find me a proof on the internet, show me a video that proves it. This experiment can be done at home ...and again i say that scientists have no idea. In the last year, the greatest scientists talk about how they were wrong about the age of the universe. Many theories are proved to be false. If you can believe that consciousness, DNA, blood, emotion, the human being was created from stone just because some smart scientist said so, then i dont have any word to speak with you .
@AlPottoff
9 ай бұрын
This sounds like BS. Too many terms like “seems to work this way” and”still not understood”. So basically just a subjective interpretation ….like all the rest …..
@HayzerX
Жыл бұрын
I see it as you explaining them being correct rather than wrong. What is erroneous in picking a subset? The fact that the results were hiding in the unassuming blur, is even more fascinating.
@shurmurray
7 ай бұрын
Thumb up for the attempt, but i think this explanation still flawed. Not inline with some of descriptions of original quantum eraser experiment setup.
@spiros252
Жыл бұрын
Wheeler delayed-choice experiment: A very distant quasar is gravitationally lensed by an intervening galaxy. We can sample photons either through an interference pattern, verifying that they passed around both sides of the galaxy, or by placing separate directional detectors that will detect they went only one way around as particles (which will destroy the interference pattern). Moreover, we can decide which experiment to perform after the photon has passed the galaxy, at the end of its path. Thus, the configuration of the latter parts of the wave appears to be able to alter the earlier history. TO WRITE THE PAST is the correct (but not rewrite). (Its possible to erase the past via other method)
@andrewbodor4891
Ай бұрын
Ash I You assume that the photon remains as a single linear stream of photons. What if something else is taking place. A light source such as the neon gas; electrons are excited to a higher energy state and when they tumble back, a photon is generated. If we follow, Gedanken experiment, we will se that the light is transmitted in a spherical shape, in all directions. As the sphere expands we see no decrease to the number of photons. The area of the surface of the sphere increases exponentially and the photon can be viewed from any angle and it will still be there. Imagine a runner on a race track where with every step that the runner takes additional runners are added. First two; then each runner adds two, to fill in the surface of the expanding light “wave” front with photons. The double slit experiment should take into consideration that no matter how carefully only a single photon is ejected toward the slits, multiple photons reach the slit on either side. Photon or photons enter the slit and immediately the photons give birth to additional photons causing the slit to act like a single light source that radiates in all directions along the plane of the slotted barrier. When you add two slits, the light from the two slits interact to create the interference patterns. The slit acts like a doorway, perhaps allowing only one photon through, but then the photon starts having babies. If you have two sets of slits, one feeding the other on from of it, by the time the photons reach the second set of slits, perhaps we will see another interference pattern on the detectors. Imagine two pinhole cameras; the light from the first feeding into the pinhole of the second; will we still see the entire “picture” projected on a “canvas”?
@altrag
Жыл бұрын
As long as the photon arrives at the D1 detector before it arrives at the beam splitters, that would still imply that each photon "knows" which direction it will take out of the splitter before hitting it. If it didn't know ahead of time, you would expect the D1 data to be inseparable - that is, the same blob pattern would appear even when you extract the samples matching the other 4 detectors. If we lay it out in chronological order: 1) Photons are split and entangled at the BBO. 2) "Top" photon arrives at D1. 3) "Bottom" photon arrives at beam splitter and randomly heads to D4. 4) "Bottom" photon arrives at D4. 5) D1 detection corresponds with D4 detection??? Step 5 still makes no sense, regardless of whether the word "erased" is used to describe the phenomena. There is still somehow information propagating from step 3 back to step 2. Hidden variables has been ruled out of quantum mechanics via other theorems which just leaves some kind of retrocausality - or some phenomena we're entirely unaware of. Of course that's relying on two assumptions: First, that the path to D1 is shorter than the path to the beam splitters (not just the path to the final D2-5 detectors). Second, it assumes that the beam splitters are perfectly random. Looking at the Wikipedia page it sounds like that assumption may be incorrect as well, and that the position of arrival on D1 has a correspondence to the choice at the beam splitter, making it effectively deterministic in the case where the D1 path is shorter (ie: when the wave function of the entangled partner has already been collapsed), and thus nullifying the question introduced by Step 3 of my above layout.
@Razor-pw1xn
Жыл бұрын
5) yes. And no, beam splitter is 50/50 total random. If not, MC is wrong. And yes, consensus according to wiki don't accept relativistic retrocausality even though hidden variable theories are disproved, which is even weirder than the experiment itself.
@altrag
Жыл бұрын
@@Razor-pw1xn > If not, MC is wrong MC? I'm apparently failing my acronym game at the moment. > don't accept relativistic retrocausality even though hidden variable theories are disproved The idea presented in the Wikis is that neither are needed. As described, the wave function collapse fully determines the output of the detectors, regardless of whether the collapse happens at D1 or at the beam splitter. Beam splitter first -> collapse at splitter corresponds to the position on the D1 detector. D1 first -> collapse at detector corresponds to the path selection at the beam splitter. It may seem odd that the beam splitter is no longer "random" in the second case, but if you think about it its not much different (conceptually) from placing a detector at the slits in the basic double slit experiment - forcing the wave function to collapse "early" removes the interference that would otherwise be expected. You still see _an_ interference pattern at D4 (and D1 after separation), but that's not from the beam splitting, its because you still don't know which slit the original photon came through prior to hitting the BBO. The only real difference is that the collapse is triggered by the entangled partner rather than collapsing the photon's own wave function. But that's obviously acceptable as that's the definition of being entangled.
@Razor-pw1xn
Жыл бұрын
@@altrag MQ sorry, it's quantum mechanics. And sorry again, I don't agree with your explanation. The beam splitter is unrelated to the collapse of the wave function. And if the photon collapses into D1 first, it cannot correspond to an idler path which has not yet been decided, at least relativistically speaking. Definitely, the beam splitter does not collapse nor can it alter "which way information". The detectors do so only in this experiment and only at the instant in which the photon is absorbed by the detector(s).
@altrag
Жыл бұрын
@@Razor-pw1xn > The beam splitter is unrelated to the collapse of the wave function Is it though? The beam splitter in itself does not collapse the wave function, that is true. But its necessarily related to the wave function itself - it transforms a wave function that has 100% chance of going "straight" into a wave function with a 50/50 chance of going one of two directions. > nor can it alter "which way information" It creates its own "which way" information - the resultant split beam will collapse on one of the two detectors on the other side of the splitter. It won't hit both. It definitely won't alter the "which way" information from the original slits, that's for sure. That's why I noted that you'd still see _an_ interference pattern. Just that the one you see isn't caused by the splitter itself. Its neither gaining nor losing any information from the original slit pattern interference. What the splitter is doing is dividing up that original slit pattern interference into two paths. In principle that should be happening completely randomly, but the fact that D1 can "predict" that secondary split indicates that there is some form of information being transferred (via the entanglement) _before_ the photon hits the beam splitter. There is only three ways that can happen: 1) Hidden variables. Already known to be false, as we've both agreed. 2) Retrocausality. The idler photon sends information back in time when it collapses on D2-5 and pre-facto modifies the path of the signal photon. 3) Forward causality. The signal photon's detection at D1 directs the path of the idler through the beam splitter. The third option is what the Wikipedia article is suggesting. Its much more "acceptable" so assume the beam splitter's 50/50 functionality breaks down when the wave function has already collapsed than it is to assume causality is broken. Of course "acceptable" is not the same as "correct". At the end of the day we don't have sufficient knowledge to say with certainty how any of that works (same as with the rest of QM), we just know that it does and the "why" of it is more a subject of interpretation than factuality. An interpretation such as pilot wave theory for example eliminates the whole question entirely as you can just assert the pilot made the choice long before any actual detection was in question on any of the detectors. Many-worlds can state that the "incorrect" results do happen but the probability of them happening is so infinitesimally small that we'll only ever see the "correct" outcomes, etc. The retrocausality question really only matters to the Copenhagen interpretation (at least among the ones I'm aware of - there's probably others). And of course to classical interpretations, but classical interpretations of quantum mechanics don't really work in any context so that's kind of irrelevant.
@HarryHeck2020
Жыл бұрын
No. When you look at where the paired photon collapses on D1 that also was detected at D4 and D5, AFTER THE COLLAPSE of the paired photon at D1, and you sum all the pairs from only D4 or D5 you get an interference pattern in that data from D1. If you sample the opposite detector's pairs they produce an inverted interference pattern. Of course the sum of all detections from D4 and D5 are going to be 100%, it is a 50/50 splitter in the eraser. The point is, the "subset" you are dismissing IS the paired photon that is collapsing in a spot on D1 that is in line with interference from BOTH slits simultaneously. What you're doing is looking at the whole and willfully tossing the paired data aside as being "a selected subset". The paired data is not selected, it is intrinsic, you cannot dismiss it for comfort.
@adamsmith7885
8 ай бұрын
5:00 a detector is made of particles which also can be put into superposition. a photon interacting with a detector is not an irreversible event since the detector itself can also but put into superposition.
@KeithMoon1980
9 ай бұрын
Watched 4 "debunking" explainer videos about this in a row, and this is the first one that I've understood. The key part being that the BBO crystal is, itself, a measurement. With that key piece of information, the rest made sense.
@TheBiggreenpig
Жыл бұрын
I'm glad you clarified this in a way, even I can understand it. But i'm sad we won't be able to send messages into the past.
@stevesmith3106
Жыл бұрын
If the entangled pairs decohere in the crystal after the slits then there should never be an interference pattern at ANY detector.
@rivertaig8703
Жыл бұрын
I watched this for the first time two weeks from now but didn’t understand it. But then I watched it tomorrow and finally understood it yesterday.
@jamesmdr_
9 ай бұрын
And when the fotons are measured after and not before the double slit wall? I would like to see an explanation about the weird results also!
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