The Delayed Choice Quantum Eraser, Debunked

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Sabine Hossenfelder

Sabine Hossenfelder

Күн бұрын

Check out the math & physics courses that I mentioned (many of which are free!) and support this channel by going to brilliant.org/Sabine/ where you can create your Brilliant account. The first 200 will get 20% off the annual premium subscription.
The delayed choice quantum eraser is one of the weirdest, if not THE weirdest, experiments in quantum mechanics. It supposedly rewrites the past because the choice of a measurement changes what happened in another measurement earlier. In this video I explain why this is not what's happening. The quantum eraser isn't remotely as weird as you may have heard.
Sean Carroll's blogpost is here: www.preposterousuniverse.com/...
Technical remark: You can find a lot of webpages saying that the envelope of the double-slit interference pattern is that of the single-slit diffraction pattern. Note that this is is only approximately correct.
You can support our channel on Patreon: / sabine
0:00 Intro
1:45 The Double Slit
4:17 Entanglement
4:53 The Quantum Eraser
9:03 What they didn't tell you
11:45 Sponsor Message
#physics #quantum

Пікірлер: 5 600
@pbsspacetime
@pbsspacetime 2 жыл бұрын
Sabine, this is amazing. You are, as usual, 100% right. The delayed choice quantum eraser is a prime example of over-mystification of quantum mechanics, even WITHIN the field of quantum mechanics! I (Matt) was guilty of embracing the quantum woo in that episode 5 years ago. Since then I've obsessed over this family of experiments and my thinking shifted quite a bit. And then I procrastinated on filming the retraction! Thanks for laying it out more clearly than I could have. I have some thoughts to share that might add one more nail to the coffin ... coming to a video real soon!
@rayfangrui
@rayfangrui 2 жыл бұрын
This is the kind of mutual respect that real scientists have for each other!
@AndronikosKoutroumpelis
@AndronikosKoutroumpelis 2 жыл бұрын
Congrats for your response Matt, others would be "insulted"
@eewls
@eewls 2 жыл бұрын
I learned to trust my intuition from QE. If the particulars of the experiment design confuse me too much, there must be something off.
@frede1905
@frede1905 2 жыл бұрын
Huge respect for your honesty. I am looking forward to your extra info on the topic!
@IncompleteTheory
@IncompleteTheory 2 жыл бұрын
In the spirit of Space Time videos without the comment checks: "The 2nd part of Matt's response was quantum erased and will have been restored in some past comment."
@liesdamnlies3372
@liesdamnlies3372 2 жыл бұрын
I’m glad you recognized the most important thing here: You can never have enough videos of kittens in boxes.
@Dziaji
@Dziaji 2 жыл бұрын
The prime rule of the internet.
@spiralsun1
@spiralsun1 2 жыл бұрын
✊🏻❤️‍🔥 Love wins! Unleash your kitties!
@Lurieh
@Lurieh 2 жыл бұрын
As long as they're not Schrödinger's experiments.
@EtienneMaheu
@EtienneMaheu 2 жыл бұрын
She should make one!
@sgalas1
@sgalas1 2 жыл бұрын
So the combined photons detected by D3 + D4 produce a non-interference pattern. But why, when viewed separately, do they each produce an interference pattern at all? Why not just a random subset of photons from the combined pattern (since the detections at D3 and D4 are randomly determined by a beam-splitter)?
@The_Trojan
@The_Trojan Жыл бұрын
Yes, I would love to have Sabine explain that. As far as I can tell it is a big hole in the explanation given in this video. Surely if Sabines logic is correct both measurements should result in similar blobs (that just take twice as many photons to produce as 50% are excluded).
@kanein3d
@kanein3d Жыл бұрын
Exactly what I was thinking, D3s pattern would just be the same pattern as D4 except with half the photons removed. If it’s an interference pattern, combining both D3 and D4 would be the same pattern just twice as strong.
@dunbabin
@dunbabin Жыл бұрын
@sgalas1 - I had the same question!! But I think I have it now... I don't know much about beam splitters, but most things can not make "random" choices. She says "the interference pattern really comes from selectively disregarding some of the particles". I think she is referring to the beam splitter causing the pattern...
@argfasdfgadfgasdfgsdfgsdfg6351
@argfasdfgadfgasdfgsdfgsdfg6351 Жыл бұрын
I thought the same thing. Needs clarification!
@yourfutureself4327
@yourfutureself4327 Жыл бұрын
"The non-quantum delayed choice eraser" by craig gidney might help
@woogemooge
@woogemooge 4 ай бұрын
I’ve watched a dozen hours of your content. SO amazing. I got curious about double slit expt after coming across a Short from another channel. And then searched for double slit content and found your channel. You had the most accurate and precise explanation of things - the other videos were approximating some of the details and were therefore confusing me. Awesome channel, love it.
@Disappearation
@Disappearation 2 жыл бұрын
Finally someone actually explains it instead of pretending to explain it while mystifying it further.
@adrianflo6481
@adrianflo6481 2 жыл бұрын
These people rely on the youtube algorithm for money, not being truthful to science. Shrödingers cat has done absolutely nothing for the betterment of understanding in popular knowledge either. Some things should not be simplified down. If someone doesnt contain the requisit capacity to undersand you shouldn't try to teach them. You just end up with confused people who spread false information.
@trucid2
@trucid2 2 жыл бұрын
Goes to show that even most physicists don't understand the concepts they talk about, they merely parrot what they've heard others say.
@rbr1170
@rbr1170 2 жыл бұрын
@@adrianflo6481 I really hate that especially those who present their interpretations and metaphors and then say "the math is correct" so what they are saying should also be true. What a B.S! The math maybe correct but your interpretation is wrong. There is only one type of interpretation which is useful and that science should trust: a geometric interpretation. If you have a mathematical formula, interpret it using geometry to communicate it to the public. And then, make those who are interested to learn more and know its application by teaching them how to do your math. Other than that is how we get multiverses and holograms that don't even make scientific sense. Where is Popper's science now?
@circumsizedmind
@circumsizedmind 2 жыл бұрын
@@adrianflo6481 wow, now you are bringing the irreducible complexity. Btw, there are a lot of PhDs in photos that didn't grok the quantum eraser experiment. Or at least not many demonstrated a good comprehension
@circumsizedmind
@circumsizedmind 2 жыл бұрын
@@trucid2 there was a joke about maths or physics professors explaining a topic and asking the students is they did understand everything. After they said yes, he looks at the board and says :and I after 20 years still don't fully. understand it....
@mureebe1
@mureebe1 2 жыл бұрын
"Ackchyually", upon returning to point A, the captain can be any age 46 or above, as we do not know the length of the voyage.
@nictamer
@nictamer 2 жыл бұрын
The voyage is 100 km, you didn't pay attention! What we really need to know is how close is his birthday.
@K9Megahertz
@K9Megahertz 2 жыл бұрын
Also need to know his speed, that wasn't specified. Could have taken him 2 years to go 100km. I'm sure that's not the case, but it is a possibility.
@nictamer
@nictamer 2 жыл бұрын
@@K9Megahertz a container ship will typically go at about 10 knots at their minimal cruising speed, so it will do 100 km in just a few hours. Unloading can take a few days depending on circumstances, so the speed is not significant.
@jamiegagnon6390
@jamiegagnon6390 2 жыл бұрын
@@K9Megahertz You are still trying to parse all of the irrelevant information. The only thing of relevance is the stated age of the captain. It says the captain is 46 years old, not was.
@jonathansturm4163
@jonathansturm4163 2 жыл бұрын
@@jamiegagnon6390 Thanks. I used to teach my clients how to think. I’d give everyone in the group a double-sided page of questions. At the top of the first page was the instruction: read through all of the questions before proceeding to write answers. The last line of the the list stated: “do not answer any of the questions. Just write your name at the top of the page and sit quietly for a few minutes.”
@paulyberk
@paulyberk 2 жыл бұрын
"You can find any pattern you want if you're willing to ignore enough data." -Matt Parker Wonderful explanation of this experiment and eye opening to me.
@theoldleafybeard
@theoldleafybeard Жыл бұрын
And so do many keep on ignoring God within us for as long as they want. 😐
@randommans3407
@randommans3407 Жыл бұрын
3:24 you lost me, the difference between getting a wave function from the double slit expirment and getting direct hits is when you measure it going through the split and if you unplug the sensor than you will get a huge wave function, you still get a slight wave function with the sensor turned on because there's space between the split and the photoelectric sheet where you observe the proton which means that it's gets turned back into a wave once it passes the sensor but because there's no two slits after the sensor so it's less random and won't be as spread apart but every once and a while an atom or particle will shoot off to one of the sides more than most particles ,but it's just not as probable, you try to rationalize it by combining the two blobs using math but that just illogical because ofcourse most of the locations are gonna average in the middle because that's just the more probable outcome, and based on our current equations to model the collapse of the wave function this is true, so explain to me how you can rationalize that, the whole premise of your argument is wrong lmfao. Literally if you send particles through one at a time they will end up in different location each time it's just more probable for the to be in the middle but when there's two slits the probabilities collide with each to create a more random outcome lmfao so when you collapse the wave function before the split it's less random because there's less probable outcomes lmfao. Like I seriously don't know what this bitch is on. She still doesn't confront the fact that our observation cause the wave function to collapse which is pretty much what the double split and quantum eraser prove.
@randommans3407
@randommans3407 Жыл бұрын
@@theoldleafybeard ik right thank God another based person in this comment section
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
*****HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!******* The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. The The three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@dragoscoco2173
@dragoscoco2173 Жыл бұрын
@@randommans3407 This is doable by a 1$ red laser and 2 human hairs on an scotch tape. 2 hairs makes a nice spaced interference pattern, 1 hair makes just a diffraction pattern, which is exactly like a double hair interference pattern just much much wider, as if the two slits were closer (because they are).
@boneladders
@boneladders Жыл бұрын
thank you so much for the work you do!! i've been interested in quantum mechanics since i was a teenager and your channel has been the perfect next step in expanding that interest 💙
@johneagle4384
@johneagle4384 2 жыл бұрын
"I think they are all wrong.." You've got to love Sabine. I believe the number of friends she has decays as fast as Fr-87.
@Webfra14
@Webfra14 2 жыл бұрын
Maybe, but the ones that are still there, will last forever.
@sjzara
@sjzara 2 жыл бұрын
The thing about science is that disagreements are commonly friendly. What looks like an attack on someone is nothing more than a challenge to an idea.
@rreiter
@rreiter 2 жыл бұрын
@@sjzara Imagine if Nature allowed video submissions for the correspondence in "Matters Arising"...
@johneagle4384
@johneagle4384 2 жыл бұрын
@@sjzara I am only joking....But, some people are weird, and some do not like to hear things like "you are wrong". Some take offense, specially Physics PhDs who have been working on a particular field for many decades. By the way, I've seem mature scientists at each other's throats because of scientific disagreements. This behavior is becoming more common.
@pedrolmlkzk
@pedrolmlkzk 2 жыл бұрын
friends are passing, truth and integrity is forever
@patrickegan8866
@patrickegan8866 2 жыл бұрын
Would love to see someone film the actual experiment rather than just seeing it animated. Thank you for the clear explanation
@AashishVishwakarma
@AashishVishwakarma 2 жыл бұрын
I've seen the exact experiment, and I personally think the animation does more justice to explanation than the actual video. Personally I think animation works very well for College or even early PhD level students to get a better sense of what's going on. Of course, people working on this domain may want to know more about the set-up.
@adventures_w_otto1370
@adventures_w_otto1370 Жыл бұрын
SHHHH. If you talk about that out loud ''THEY'' might hear you. ᶜᴾᵁ > ᴳᴾᵁ > ᵀᴴᴱ ᴰᴿᴱᴬᴰᴱᴰ ˢˢᴰ ᴬᴿᴱ ᴬᴸᴸ ᴬᴺᴵᴹᴬᵀᴱᴰ. [ᴮᴱᵂᴬᴿᴱ ᵂᴬᵀᶜᴴᴵᴺᴳ], ᴴᴼᵂ ᴬ ˢˢᴰ ᵂᴼᴿᴷˢˀ ʸᴼᵁ ᶜᴬᴺ'ᵀ ᶠᴵᴺᴰ ᴬᴸᴵᴱᴺˢ ᴮᴱᶜᴬᵁˢᴱ ᴬᴸᴵᴱᴺˢ ᴬᴿᴱ ᴺᴬᴺᴼᵎ ''ᵀᴴᴱ ᶠᴵᴸᴱˢ!'' kzbin.info/www/bejne/gpDSkIJtq5aYrdU
@phumgwatenagala6606
@phumgwatenagala6606 Жыл бұрын
TheActionLab did one recently
@howdareu7529
@howdareu7529 Жыл бұрын
i would like to see "globe from space,not cgi ed
@btd6vids
@btd6vids Жыл бұрын
I know this is super late but it’s actually possible to do at home, you just need a laser pointer as the only thing you might not already have, and you can get those for like 5 bucks. “I did this by taking a piece of glass and holding it over a candle to get a nice thick layer of black soot on it, then holding two x-acto knife blades parallel to each other and scraping two nice thin lines right next to each other in the soot.” You can probably do this with razor blades or anything similar to it, and you can even use aluminum foil instead of the glass (but be aware that the foil will tear super easily)
@Porquetegusta
@Porquetegusta 10 ай бұрын
I love this video. I couldn't find another one that explained it so well. concrete and simple. Excellent, it shows that you know what you are talking about. please do not stop making these jewels!
@DeSinc
@DeSinc 2 жыл бұрын
I've looked on several occasions for a video like this to describe what is actually going on but all I could find was videos of people saying the particles act differently based on if you observed them or not which just always frustrated me to hear. finally now I have a video that I don't completely understand but at least can point to when people bring this topic up.
@Lucky10279
@Lucky10279 2 жыл бұрын
If you're still struggling to understand, this video is also really good: kzbin.info/www/bejne/n6qxY2qIbLp3pKs
@_whatthefacts_
@_whatthefacts_ 2 жыл бұрын
I always point my mates to "Glitches and tricks in Half Life 2" when I need to explain quantum weirdness.
@sashas3362
@sashas3362 2 жыл бұрын
@@_whatthefacts_ The unexplainable disappearance of the wavelike interference pattern of the single particle double slit experiment when the which-way info is detected has been cited as proof of "simulation theory" (the theory that reality is a computer simulation). It's claimed this otherwise unexplainable phenomena can easily be explained/understood as a more detailed rendering. The wavelike interference pattern is explained as a less detailed rendering which appears when you aren't looking at which slit the particle went through. It's like a crappy rendering engine with noticeable "glitches".
@pflaffik
@pflaffik 2 жыл бұрын
DeSinc, Sabine doesnt question that the particles act differently based on if you observed them or not, thats a fact and she confirms it in this video.
@quattrocity9620
@quattrocity9620 2 жыл бұрын
@@pflaffik That's not what I got at all here... The particles didn't behave differently , we just observed them differently. I could be wrong but it seems she was saying that we observed the particles without the which way information. Don't murder me on here, I'm obviously not a quantum physicist and it's possible (if not likely) I misunderstood this video.
@feynstein1004
@feynstein1004 2 жыл бұрын
Everyone: The delayed choice quantum eraser is impossible to understand. Sabine: Hold my Bier
@jirijelinek2038
@jirijelinek2038 2 жыл бұрын
More like "Hold my beer, I'll present Sean Carroll's explanation."
@feynstein1004
@feynstein1004 2 жыл бұрын
@@jirijelinek2038 Fair enough 😂
@p-j-y-d
@p-j-y-d 2 жыл бұрын
Not fair. The didactic value here is higher.
@Sharperthanu1
@Sharperthanu1 2 жыл бұрын
@@jirijelinek2038 Richard Feynman says that Sean Carroll's explanation is crap so forget it.
@brian.josephson
@brian.josephson 2 жыл бұрын
Listen at 0.75 speed and it'll be clearer.
@finelinerin
@finelinerin 5 ай бұрын
Danke, vielen Dank! Ich kehre immer wieder hierher zurück, wenn ich verwirrt bin. Super Präsentation. Klar und einleuchtend. Und die Didaktik im Video - einfach genial 🙏🏻
@CalamitousProphet
@CalamitousProphet Жыл бұрын
I would very much appreciate clarification on the nature of a particle detector in reference to the double slit experiment. It is frequently implied that observation itself is the cause of wave function collapse, rather than any force imparted by the measurement device. This can be pretty frustrating when trying to understand the why behind these things.
@DavidByrden1
@DavidByrden1 11 ай бұрын
Relax. No need to be frustrated. Because "wave function collapse" does not exist. You don't need to worry about what causes it. When the particle hits the detector, its wave function becomes entangled with the detector, resulting in a whole continuum of detectors in parallel universes, each registering a "hit" in a different spot. And the effects propagate until there is a continuum of multiple copies of YOU, each seeing a "hit" in a different spot. Nothing collapses. Yes, I know that I sound insane here, but I'm simply telling you exactly what the Wave Function says. This was clarified by Everett many years ago. And once you get used to the "many worlds" interpretation, you become the thing that Feynman didn't believe in : a person who understands quantum mechanics.
@maxbro16
@maxbro16 6 ай бұрын
@@DavidByrden1 lol wut?
@kdub9812
@kdub9812 3 ай бұрын
collapse is an illusion, it is an artifact of perception. it only appears to happen given one’s limited appearance of reality
@kingo_friver
@kingo_friver 2 жыл бұрын
I've already given up to understand this topic after watching all those videos several times. Finally, today I got satisfaction, even though I still need to rewatch this several more times. Thank you so much!
@lubricustheslippery5028
@lubricustheslippery5028 2 жыл бұрын
I also have to rewatch the video. Still don't understand why the detectors can change the interference pattern.
@needmorespaceformyna
@needmorespaceformyna 2 жыл бұрын
@@lubricustheslippery5028 In the regular double slit you mean?
@m.c.4674
@m.c.4674 2 жыл бұрын
@@lubricustheslippery5028 It doesn't change the Interference pattern . It will help if I explain how the sector works . The detector , when on blocks the light , but when it is off allows the light to pass through , it is literally that simple. Next , inorder to create a interference pattern two beam of light need to over lap with each other and undergoes , destructive and constructive interference . Now I want you take another look at the experiment . You will see that the detector was on ,which prevents the second beam of light to interfere with the first beam of light , thus there is no interference pattern . Now move the detector further back than the screen . The dector being on doesn't affect the light pattern in the future . The light beam simply does what It would normally do when there is no other light to interfere with . At this point you should realize the word trick that was being played on you. I don't only disagree with the idea that causality is broken , I also disagree that the direction of the beams of light are erased , because as you can see the light is slit into two when the detector is off , so if I put a screen their I see light . It is literally that simple.
@kingo_friver
@kingo_friver 2 жыл бұрын
@@lubricustheslippery5028 We are enjoying to understand what we don't yet know😊 It's ok that I don't understand all the details, as these science experiment and math are not hands-on for me anyway. But I've just wanted a rational explanation for this fascinating topic.
@louferrigno4712
@louferrigno4712 2 жыл бұрын
​@@lubricustheslippery5028 Don't over complicate it. On detectors D3 and D4 each detector receives two beams of photons. One of the beams goes through a beam splitter, the other beam does not. The splitter reflects 50% of the wave basically cutting a sine wave in half. The patterns that show up are the gaps in the data from the reflected portion of the wave. It seems to be a test set up to see if you can predict one photon by measuring it's entangled counter part that got misconstrued.
@atlanticx100
@atlanticx100 2 жыл бұрын
You are the first one on youtube that I have seen to take the magic out with a fuller explanation. Thank you.
@preppen78
@preppen78 2 жыл бұрын
I'm just happy the kitten was alive
@vladimirseven777
@vladimirseven777 2 жыл бұрын
The one that turned fuller explanation into working clickbait (I definitely clicked). Others are fine by using magic in their videos to get views and sponsors.
@DrSharoyko
@DrSharoyko 2 жыл бұрын
not true: kzbin.info/www/bejne/fXfVhGOIq5uCiqc
@atlanticx100
@atlanticx100 2 жыл бұрын
@@DrSharoyko Never saw that one thanks.
@fatfrumos1163
@fatfrumos1163 2 жыл бұрын
Check Science Asylum video on this. I think he was the first to demystify the situation
@timoluetk
@timoluetk 2 жыл бұрын
This is an amazing addition and quite fundamental to understanding what is actually going on. Thanks Sabine!
@rupendradhillon
@rupendradhillon Жыл бұрын
Mam, I saw your video and I am a fan. For the last 10+ years I've been trying to understand how at once, when observed the interface pattern turns into two neatly separated points. You are literally the first person to call that out and call BS on these other "so called physics" channels. Thank you so much ! Maybe, could you also do a video on your views on the single slit experiment. e.g. Why you think it might be happening?
@samsam2235
@samsam2235 2 жыл бұрын
Sabine calling out the YT physics boys. You gotta love it.
@andrearaimondi882
@andrearaimondi882 2 жыл бұрын
Sabine adding Joe among the KZbin physics guys. That's an acknowledgement!
@isonlynameleft
@isonlynameleft 2 жыл бұрын
@@andrearaimondi882 Joe is not a phisicist so I don't really expect him to have that level of knowledge but if you're a phD physicist you really should know better!
@alphagt62
@alphagt62 2 жыл бұрын
@@isonlynameleft and that’s the thing. So many physicists don’t really understand what they are teaching. They’ve gone through the school, and passed the classes, but they fail to achieve Sabine’s level of understanding.
@d.t.4523
@d.t.4523 2 жыл бұрын
If you're any good at physics, you probably have better things to do than sensationalize video content on the web. 👍
@jonathansturm4163
@jonathansturm4163 2 жыл бұрын
@@alphagt62 This!
@Jason608
@Jason608 2 жыл бұрын
Thank you SO much for this video. My favorite on your channel so far. I had read about the double slit experiment years ago and had been confused, but your explanation at 3:03 is a complete game changer and cleared up all my confusion about how this supposed paradox works. Again THANK YOU!
@scotvaka1t375
@scotvaka1t375 2 жыл бұрын
This amazing video is a perfect example why I am a subscriber to your channel. You have inspired me to start my own theoretical physics channel. I intend to cultivate discourse to create progress. Thanks Sabine!
@user-zp4jt6vx6l
@user-zp4jt6vx6l 11 ай бұрын
I was deciding on which video should pop my q-eraser Cherry and selected yours first. I LAUGHED when you referred to all of the others. I chose well!
@markpaterson2053
@markpaterson2053 2 жыл бұрын
Where have you been all these years, Sabine? You are truly the only scientist capable of translating/adapting/simplifying/whatever the problem of grasping things that others deliberately romanticise.
@stefaniasmanio5857
@stefaniasmanio5857 2 жыл бұрын
She has been working and studying quite hard …
@massimiliano-oronzo
@massimiliano-oronzo 2 жыл бұрын
S. Hossenfelder is not a superhero. In science some perform experiments and try to give an interpretation, others (rightly) raise criticisms. This is how it works. At the end of the 19th century, almost all physicists thought that light must necessarily propagate through an ether.
@jeffriesmovies
@jeffriesmovies 2 жыл бұрын
There are so many great science communicators beyond your youtube algorithm
@cristianproust
@cristianproust 2 жыл бұрын
"deliberately romanticize" how can that be romanization if it is perfectly consistent with time not being experienced by a photon?. Wouldn't that be the expected result?. What it is a romanization it is to think that this experiment not appearing conclusive to reiterate the result that time is not real as we perceive it, and that it would mean things still have a chance to evolve unexpectedly. People who romanticize having free will have more interest in this experiment being not being conclusive than the other branch that see it as a result perfectly consistent with Relativity
@justdave9610
@justdave9610 2 жыл бұрын
She's one of my favorites because of how she tends towards skepticism and isn't afraid to call bs when she sees it even despite how doing so risks creating animosity with others in science and physics. Also she's really good at explaining physics in a practical, straightforward, and understandable way without dumbing it down too much
@PSG_Mobile
@PSG_Mobile 2 жыл бұрын
I still dont understand why D3 and D4 have complementary patterns that look like interference instead of complementary patterns that look like normal distribbution.
@AdamJMilward
@AdamJMilward 2 жыл бұрын
Me too. Since the half mirror randomises the photons that go to D3 and D4 why do those randomly selected groups of photons each produce an interference pattern.
@ThePinkus
@ThePinkus 2 жыл бұрын
Below is the very same post as I used in the reply to a very similar question elsewhere. It is not a satisfactory answer. The reference is to equation 10 in arXiv:quant-ph/9903047v1 (figures 3 and 4 in the same). Note: in the article the eraser path has D1 and D2, which is opposite to the notation in the video. The setup is in figure 2. I would lie if I told You that I can really follow through the derivation. What I can sum up: the conclusion is that there is a phase shift between the two patterns in (10), one with cos^2( x pi d / lambda f) the other with sin^2([same]), so that when we sum the two patterns these two terms sum to one and only sinc^2(x pi a / lambda f) remains (which looks as a blob with no interference-like bands); in turn, this comes from eq. 4, where "the different sign between the two amplitudes [...] is caused by the transmission-reflection unitary transformation of the beamsplitter BS [ref. to rig. 1 and 2]". I think this is also to be considered in combination with the computations after eq. 4, which include the paths' lengths. If I understand it correctly, it is a matter of different path lengths combined with the different effects on the phase of transmission-reflection at the beam splitter that causes the shift between the patters, but I might be wrong.
@PSG_Mobile
@PSG_Mobile 2 жыл бұрын
@@ThePinkus thanks for answer! So, if you are right, this interference pattern has nothing to do with wave functions, it is just Optics.
@ThePinkus
@ThePinkus 2 жыл бұрын
@@PSG_Mobile Current optics is done by wavefunctions, in fact the computation we find in the article derives the results as a "standard quantum mechanical calculation" (pg.2 just before eq. 1), and the equations are not classical wave optics, but quantum field theory. So, correct, it is optics, hence, of course, it has everything to do with wavefunctions. Best regards!
@PSG_Mobile
@PSG_Mobile 2 жыл бұрын
@@ThePinkus thanks!
@celivalg
@celivalg 8 ай бұрын
I did find a debunking of this problem on youtube a few years ago, but I couldn't find it again when I wanted a refresher and found your video instead! thanks a lot!
@anttikorpinen3977
@anttikorpinen3977 2 жыл бұрын
Thank you for the awesome explanation in video format. When those videos you mentioned were published, I spent days on the internet reading various forums to find the same anwer you presented. If only this video would have been available at the time. Subscribed.
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
SABINE NONSENSE IS DEBUNKED BY NOBEL PRIZE 2022 WHICH PROVES ENTANGLEMENT IS REAL! The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. All three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@BluesDoctor
@BluesDoctor 2 жыл бұрын
As usual, Sabine presents her deep insight in a conceptual context that is easier to grasp, just pay attention. A gifted communicator the likes of which are quite rare. These concepts make the math and statistical probabilities easier to grasp and interpret from the bigger picture. A delight for the young pup and old dog alike.
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
SABINE NONSENSE IS DEBUNKED BY NOBEL PRIZE 2022 WHICH PROVES ENTANGLEMENT IS REAL! The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. All three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@Bodyknock
@Bodyknock 2 жыл бұрын
Just FYI in the two PBS Spacetime videos after the one mentioned here they do talk more about how the two interference patterns combine to form the single blobby image you get from the which-way detectors. In particular he talks about how the interference patterns are actually partitions of the original set of photons based on the characteristics being measured by the combined detectors C or D at the end. So there's no way to know in advance which photon is going to be in which interference pattern until you actually get the measurements from those two detectors. He uses this as an example of why you can't build a "time machine" that sends morse code signals by placing or removing the mirrors at the which-way detectors to send a message back in time based on seeing or not seeing an interference pattern. The image you see is always the same, it's just whether you're categorizing the photons as two combined interference patterns or one blob and you can't know details about the interference patterns embedded in the image until you get the measurements.
@AashishVishwakarma
@AashishVishwakarma 2 жыл бұрын
Indeed! Matt even made a competition our of it if I remember correctly!
@somebodysomewhere5571
@somebodysomewhere5571 2 жыл бұрын
People may get too caught up in the time aspect and fail to realise how mind blowing it is that just by measuring the data is collapsed which is the best part
@Littleprinceleon
@Littleprinceleon 2 жыл бұрын
But why does the separation of photons into those two groups even create a pattern which looks like as if there was interference? Why is it so that those photon-pairs that end up in one of the "after erasure" detectors can not hit certain locations on the screen? And the other half - in opposite - hits these bands on the screen, so the second pattern is shifted exactly to match the "negative" of the first: except - if I understood correctly from a real published study and not some interpretations - the two patterns are almost the same just shifted...
@janPeja
@janPeja 2 жыл бұрын
@@Littleprinceleon As far as I understand it, it's like releasing rabbits towards a carrot and a lettuce pile. Later you measure the color of their poop and realize all green poop rabbits interfered with lettuce pile and orange poop rabbits with carrot pile. It's not like measuring their poop caused them to retroactively choose a certain pile. :D
@Littleprinceleon
@Littleprinceleon 2 жыл бұрын
@@janPeja but why did half of them choose one pile at all? The paths to the "erasure" detectors are symmetric: only difference is that the photons leave the BBQ crystal at two different sites depending on the slit they "went through". That's what Sabine emphasizes: the which way information is "detected" and transferred by the crystal (absorption, reemission). That in the end we combine the information doesn't seem to "erase" anything. We only obscure the direct info on the path for ourselves. So another relevant Q: are the particles distributed in the same two patterns on the "screen" if we detect their entangled pairs at the earlier "which way" detectors? And we just cannot obtain the right information with this setup of the detectors? Is the result random and the pattern emerges because of some property (phase? polarization?) of the photons? Just like with coins: two possible outcomes inherent to the object, evoked by random influences... Is this property dependent on their path ? Even if, why are there discrete bands? The "bomb experiment" implies that whenever the photon has a choice, eg. at the semitransparent mirror (beam splitter) in reality it goes through both ways: even interferes with itself... But in the case of the DCQE this happens to that part of the entangled pair detected by the "erasure" sensors. Does the entanglement influence all the information contained in the wavefunction? How big/long can be one quantum of electromagnetic wave? It seems that amongst chlorophyll molecules a photon takes many, many different paths until it "finds" the energy center.
@einfacherkerl3279
@einfacherkerl3279 2 жыл бұрын
This shows, information from unknown KZbin bloggers is not reliable. Thanks Sabine!
@PovlKvols
@PovlKvols Жыл бұрын
Great video and a great explanation, @Sabine. Keep up the good work, and thank you for sharing!
@ericknight5014
@ericknight5014 2 жыл бұрын
Thank You Sabine. I love you. I have been puzzling about this for years and can give my brain a rest and stop worrying about a patent application for long distance instant communication.
@jehl1963
@jehl1963 2 жыл бұрын
This is why I watch Sabine's channel.
@American_Moon_at_Odysee_com
@American_Moon_at_Odysee_com 2 жыл бұрын
I should have known your exposition on this experiment would be unique, enlightening, really helpful and different from even the better ones on the topic.
@darkace37
@darkace37 2 жыл бұрын
I am shocked. I feel like I could as likely won the lottery today without playing. As a quantum casual I feel somewhat betrayed by the simple explanation being disregarded. I today find myself more cynical than ever and appreciate people like you. I have neglected your channel over others and realized after the past few episodes that I have been wrong to do so.
@Aerojet01
@Aerojet01 Жыл бұрын
Even though Sadine has offered an interesting perspective, there are still many lose ends between the wave-like behaviour, and entanglement. Entanglement is still a controversial subject, and we don't know for sure how information is being shared. There's no clear evidence of a linear relationship. Until a paper has been published and scrutinized, supported by experimental data, the controversial" Delayed Choice Quantum Eraser" is still on the table.
@argfasdfgadfgasdfgsdfgsdfg6351
@argfasdfgadfgasdfgsdfgsdfg6351 Жыл бұрын
Sabine's explanation is incomplete, though. She does not explain why D3 and D4 individually would see an interference pattern at all - she says that for those detectors, scientists were "simply ignoring" 50% of the data, but that would just lead to D3 seeing a blob with half the count and D4 seeing a blob with half the count, but not in a certain pattern. Big flaw in the argument.
@psiphisapiens
@psiphisapiens Жыл бұрын
@@argfasdfgadfgasdfgsdfgsdfg6351 you have misunderstood the video
@argfasdfgadfgasdfgsdfgsdfg6351
@argfasdfgadfgasdfgsdfgsdfg6351 Жыл бұрын
@@psiphisapiens It's strikingly clear that instead of giving us insight on how exactly we are wrong, you chose to criticize us without any factual substance, which is a strong sign of a lack of understanding from your side.
@argfasdfgadfgasdfgsdfgsdfg6351
@argfasdfgadfgasdfgsdfgsdfg6351 Жыл бұрын
@@psiphisapiens That's high school physics and it doesn't even explain what I mentioned.
@AveiMil
@AveiMil 2 жыл бұрын
This video erased my previous misconceptions.
@Lin_The_Cat_
@Lin_The_Cat_ 2 жыл бұрын
3:07 Joe’s face in that screenshot of his delayed choice quantum eraser video. 😂 Gotta love him. Love this video, too! I’ve heard about how the quantum eraser experiment doesn’t actually rewrite the past; however, I love the way you explained it in this video in that it was much easier to follow.
@EM-bs4kt
@EM-bs4kt 2 жыл бұрын
That’s because her experiment is nothing like the one done by skulls Kim et al
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
*****HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!******* The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. All three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
***HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!****** The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. The The three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@NotRodShop
@NotRodShop 2 жыл бұрын
Most of the experiments that I have seen show 2 distinct vertical lines on the film plate when the "which way" information is measured. The way you are showing this is that there is one big horizontal blur when the which way information is measured. This seems to be the big disconnect in information that needs to be established more than anything else.
@ThePurza
@ThePurza Жыл бұрын
The thing I don't understand about Sabine's explanation, is that supposedly the fact that you can't see an interference pattern until you separate them by the path of their untangled pair, supposedly demystifies anything. They do result in an interference pattern when correlated with either of the paths that send the beams down a path that makes it impossible to determine which slit the photons took. it deserves more explanation as to how the merged 'interference' detections perfectly merge to a indiscernible pattern. Sabine has stated that she thinks determinism solves these things in a more recent video. That explanation makes sense to me, and would resolve this also, essentially arguing that 'Determinism' is the 'hidden variable' all along.. that wave functions take future measurements into account.
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
***HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!****** The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. The The three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.” What now?
@donwolff6463
@donwolff6463 Жыл бұрын
Thank you ever so much Sabine. Your insights and instruction is invaluable!
@X_Baron
@X_Baron 2 жыл бұрын
After reading Carroll's explanation, my understanding is that the error in the other videos is this: they show a stripe pattern appearing on the detector screen, but in actuality it doesn't. You can create a visualization after-the-fact, showing which parts of the blob pattern correspond to which measurements, and this way create an interference pattern.
@ggg148g
@ggg148g 2 жыл бұрын
Would you please give the reference to the book or article by Carroll you're quoting? Thanks
@X_Baron
@X_Baron 2 жыл бұрын
@@ggg148g The link to his blog post is in the video's description. It's apparently a section of his book that he had to edit out.
@william_benckert
@william_benckert 2 жыл бұрын
How does this disprove the mysterious aspect? The first particles are still landing on the screen seemingly dependent on the future randomly chosen destination of their pair particles..?
@Lestertails2
@Lestertails2 2 жыл бұрын
it breaks the mysterious aspect because you have causality backwards. In reality, The particles are landing on the screen, and latter they are at either detector d3 or d4. But whether they land at d3 or d4 is already determined by where they land on the screen. This effect, while weird, is just a normal quantum entanglement effect. So, your choice of using detector d3 and d4 vs d1 and d2 is not retroactively changing where the particle lands on the screen, it is only changing whether or not you apparently see an interference pattern for that grouping of particles. Does that make sense?
@william_benckert
@william_benckert 2 жыл бұрын
@@Lestertails2 Yes, the fact that the second particles "decide" whether to land on a detector with or without which-way-informatoon depending on where the first particle landed is the mystery, right? So I am not sure I get the point of the video.
@Lestertails2
@Lestertails2 2 жыл бұрын
@@william_benckert No not exactly. The apparent mystery is that you could change whether an interference pattern is observed after the first particle lands at the screen by changing between measuring with detector d1/d2 vs d3/d4. Because it is possible to make the choice of d1/d2 vs d3/d4 (hence the "delayed choice experiment") some people wrongly interpret this to mean that quantum information is sent backwards in time (spooky). Sabine points out that this is not the case. At the screen, there is no interference pattern, regardless of d1/d2 vs d3/d4. The interference pattern only apparently appears when using detector d3/d4 to match where a particle in the past landed on the detector screen. Thus where particle 1 landed on the screen will determine which detector (D3/D4) its entangled partner lands at, to make the apparent interference. This is an interesting property of quantum entanglement (and yes, quite mysterious), but it isn't "sending information back in time" mysterious.
@william_benckert
@william_benckert 2 жыл бұрын
@@Lestertails2 Uhm, either the first particles are looking into the future or the second particles are looking into the past (apparently). This video doesn't debunk anything.
@EM-bs4kt
@EM-bs4kt 2 жыл бұрын
@@Lestertails2 D3 or D4 both correspond to an erasure state. Summing the total of both is nonsense. Would you attribute a coin that landed heads today to a coin that landed tails yesterday and say that it was completely determined and dependent ?
@mschwaller3371
@mschwaller3371 Жыл бұрын
Just have to love these explanations! Thanks you Sabine!
@ShionWinkler
@ShionWinkler 2 жыл бұрын
Another great video, I love both yours and Matt's videos.
@AlleyKatt
@AlleyKatt 2 жыл бұрын
Sabine always finds a way to debunk the mystical and add wonder. Science without the bull. Love it.
@maecentric
@maecentric 2 жыл бұрын
Mysticism is positing theres a physical reality outside of your conscious experiences - a reality you never have direct access to and one which breaks down in both quantum mechanics and general relativity - and of course the physicalist abstraction never accounts for the mind experienceing it
@gwiz6278
@gwiz6278 Жыл бұрын
​​@@maecentric Through the use of ritual one can access this realm. The opposition of mysticism and science is a false dichotomy that is perpetuated by both in the current age.
@MrCmon113
@MrCmon113 10 ай бұрын
Quantum mechanics is way worse than the mystical. No matter which way you put it, something people considered obviously true has to give.
@terribleterrier1685
@terribleterrier1685 2 жыл бұрын
Thank you Sabine. This experiment always confused me and I finally understand. You make it seem so effortless! Science educators on KZbin more and more chase the clickbait as opposed to actually trying to bring understanding. I never miss one of your videos and I always come away more enriched.
@k0niczynek
@k0niczynek Жыл бұрын
OK, I have a question - what are the separate patterns from photons hitting D1 and D2 - before they are combined? Another question - beam separator at the end that lets 50% of photos pass and reflects another 50% is it like round robin thing 1 pass 1 reflect or is it random thing that over time makes up to 50% pass 50% reflect? I think you've also omitted some of the details.
@The_Trojan
@The_Trojan Жыл бұрын
Correct, there is no explanation as to why any pattern appears at all. Sure, half the photons are excluded, but why are the not excluded totally randomly? why are they excluded such that an interference pattern appears?
@eliasf.fyksen5838
@eliasf.fyksen5838 2 жыл бұрын
Omg, ever since I watched the PBS ST video 5 years ago this been bothering me, it just didn’t sit right. I have been googling the experiment ever so often (hence how I found this video) and finally someone put it a way that both made sense and let me understand what the experiment really does/what it means. Thank you so much!!!
@scptime1188
@scptime1188 2 жыл бұрын
Craig Gidney's video on the DCQE experiment actually does clear up the misconceptions you covered here too!
@francescoromano2857
@francescoromano2857 2 жыл бұрын
Wow, he really did!
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
****HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!****** The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. The The three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@randystegemann9990
@randystegemann9990 2 жыл бұрын
Yes, Peter is 46 years old, but that is at the start of the puzzle. How long did his voyages take and the loading and unloading of the ship? Especially now, with container ships waiting offshore for their turn and canals sometimes getting blocked. At the end of the puzzle we are asked how old is the captain, not how old he was.
@rog2224
@rog2224 2 жыл бұрын
Where did she say 'At the start of the voyage Peter is 46 years old' There's no implication of an actual timeline in the two bits of information - Peter's age with his job, and what happened on some unspecified voyage at some unspecified time. Peter *IS* 46 years old is the only concrete information in terms of a when, which is 'currently' the rest is just noise (unless you're in logistics, then it might be of interest)
@johnnyzee383
@johnnyzee383 Жыл бұрын
@@rog2224 Of course there is an implication of time between the 2 points unless of course you think the ship arrived instantaneously, therefore, Peter's age IS different from the start of the voyage then to its end, even if extremely slightly. "Noise" is simply someone's avoidance of measuring or determining a very very small subset of data that would be crucial to determine an outcome, otherwise the outcome would be flawed.
@vincentferrer876
@vincentferrer876 2 жыл бұрын
Brilliant! I've been looking for someone to clear this up for some time. Thank you!
@Gjallitr
@Gjallitr 2 жыл бұрын
This is such a calm and easy to understand explanation. Outstanding.
@blawrence42
@blawrence42 2 жыл бұрын
Sabine, love your channel, but I think some clarification is needed here. Yes, I think I understand the explanation being offered here that retro-causality need not be invoked to explain the outcome of the delayed choice quantum eraser experiment. And yes, I read Sean Carroll's article that offers essentially the same explanation that you do here. After all, "we can trust Sean with the quantum stuff" as you so aptly put it. But, Sean Carroll's explanation (and by extension yours) invokes the Everettian "Many Worlds" interpretation to explain away the need for retro-causality. The wave function doesn't "collapse" as it would in the Copenhagen interpretation, but rather there was a decoherence that branched the multiverse along all possible paths. But, the Many Worlds interpretation of quantum mechanics has been something that you've been very highly and very publicly critical of here in the past. If we can really trust Sean Carroll with the quantum stuff, and his explanation invokes Many Worlds to explain the delayed choice quantum eraser, then does it not follow that we should trust Sean Carroll's opinion of the Everettian "Many Worlds" multiverse upon which it depends? "There’s no need to invoke retro-causality to explain the delayed-choice experiment. To an Everettian, the result makes perfect sense without anything traveling backwards in time." - Sean Caroll, "The Notorious Delayed-Choice Quantum Eraser", Sep 21, 2019
@martir.7653
@martir.7653 2 жыл бұрын
My understanding is that one can subscribe to the "many-worlds interpretation", while considering the other universes as just a tool for the explanation, not implying they are "real" in any sense. Wikipedia has this quote from Stephen Hawking: "But, look: All that one does, really, is to calculate conditional probabilities-in other words, the probability of A happening, given B. I think that that's all the many-worlds interpretation is. Some people overlay it with a lot of mysticism about the wave function splitting into different parts. But all that you're calculating is conditional probabilities."
@xen2
@xen2 2 жыл бұрын
@@martir.7653 Here is a video about multiple time dimensions: kzbin.info/www/bejne/n5inn6SQfJVgrNU This improves on the "many-worlds interpretation" in some ways
@markfernee3842
@markfernee3842 2 жыл бұрын
There's no need to invoke the many worlds interpretation to explain the result. This delayed choice quantum eraser can be shown to be the same as Wheeler's delayed choice experiment. In that case, the detections at D0 just provide an alternative visual output for the experiment, which is nice, but nothing different.
@blawrence42
@blawrence42 2 жыл бұрын
@@markfernee3842 One can always "shut up and calculate" and perhaps this is even one of those times. But, the whole point of having an interpretation is to try to understand what the math is telling us. Yes, different "visual outputs" at D0 is empirically observed, but that alone is just ignoring the most profound aspect of the results. That is that the different outputs seem dependent on the presence, or absence, or arrangement of detectors that are further downstream in the experiment (and therefore reached at a later point in time). Sabine here is accepting Sean Carroll's explanation for the most part and then stopping short at the point where Sean actually brings the argument home that under Many Worlds this doesn't necessitate retro-causality. Sabine is trying to have her cake and not eat it too (to belabor an analogy). Even Sean Carroll in his article on the same topic acknowledges that if you subscribe to other interpretations of quantum mechanics where wave functions are considered to actually collapse then it would be understandable to invoke retro-causality to explain the outcome (though he ultimately disagrees on this point). But Sabine here seems to want to invoke all the math that Sean does, but not the interpretation that Sean does to bring it all home. In essence, Sabine just talks around the point without actually addressing it. Again, from Sean's article cited in Sabine's video: "But alas, not everyone is an Everettian. In some other versions of quantum mechanics, wave functions really do collapse, not just the apparent collapse that decoherence provides us with in Many-Worlds. In a true collapse theory like GRW [...] you can convince yourself that retrocausality needs to be part of the story. Or you can accept the smooth evolution of the wave function, with branching rather than collapses, and maintain time-symmetry of the underlying equations without requiring backwards-propagating signals or electrons that can’t make up their mind." Sean Carroll, "The Notorious Delayed-Choice Quantum Eraser"
@markfernee3842
@markfernee3842 2 жыл бұрын
@@blawrence42 the problem is that this experiment purports to be a proof of retro-causality. Retro-causality in quantum theory is an interpretational aspect that can be applied to a range of experiments. It's not just shut-up and calculate that shows no retro-causality in this experiment. One can just run through the detection chain logic without to see this. The photon pair generated in the crystal are momentum-entangled. When D0 is detected, that detection is compatible with the photon having a certain momentum. However, there is more momentum information available from the entangled partner. We just have to wait for it to be detected. Once it is detected, the particular detector, D1-D4, will determine the additional momentum information that is provided. So after the second detection, we can say more about the momentum of the first detection at D0 because we have updated out information. Where is that retro-causal? One of the main problems with how people interpret this experiment is the complete disregard for the SPDC crystal and the effect it has on the interference pattern. It completely washes out the possibility of observing an interference pattern. That's due to the finite thickness (0.3 mm) of the crystal, the wavelength dispersion in the crystal, and the random point of down conversion within the crystal. These effects were included in the Scully's calculations in the paper, but otherwise not mentioned. However, these effects are well known to anyone who works with SPDC crystals in optical circuits. From that aspect, I find this experiment somewhat disingenuous. Furthermore, the paper didn't explain the origin of the two complementary interference patterns. There should only be one Young's double slit interference pattern, not two. This is should be red flag when interpreting this experiment. It is telling use that it is not working they way we expect it does. Finally, one can actually see that this experiment is actually a rather unique version of Wheeler's delayed choice experiment by identifying the interferometer circuit. There is no "eraser", just the delayed choice outcomes as already described by Wheeler. This is rather profound, but already known. I could easily rewrite this experiment titled as, "Wheeler's delayed choice experiment with entangled photons".
@PublicVoidFoo
@PublicVoidFoo 2 жыл бұрын
I kinda feel deceived now, a critical distinction was missing from popular explanations! I'm curious, if the experiment is not showing anything new really, then what' is its significance in the scientific community?
@SabineHossenfelder
@SabineHossenfelder 2 жыл бұрын
That's an excellent question. Partly I think the reason is historical, the roots go back to an old idea by Wheeler. But I think it's also because it's more visual, as opposed to (say) Bell-type tests in which you calculate correlations. Here you have several paths on which particles travel resulting in a pattern on a screen -- lot of spatial information in this which is much more intuitive than other experiments. This is my guess in any case. I mean, the reason you see this so much on KZbin is exactly because it can be visualized with dots moving on paths etc.
@_John_P
@_John_P 2 жыл бұрын
@@SabineHossenfelder Would you be so kind to tap on the controversies of Bell's experiment?
@DrDeuteron
@DrDeuteron 2 жыл бұрын
My brilliant and world famous advisor would say "nothing". In fact, what he did say was, "Hey look: quantum mechanics works, we've known that for 100 years". Literally does not care. Nevertheless, we now have experimental techniques that allow us to probe psi in new ways, and some ppl like that. The weird stuff starts with multiple particle states (e.g., the bomb), but it's still linear mathematics and theory alway predicts experiment.
@ListenToMcMuck
@ListenToMcMuck 2 жыл бұрын
@@SabineHossenfelder Are you sure that nobody whispered the words: "Let's make it seem like it's pure magic...", while writing the paper. ^.^ ,
@kenlogsdon7095
@kenlogsdon7095 2 жыл бұрын
@@SabineHossenfelder Historically, Wheeler and Feynman were heavily into modeling QM interactions involving temporally "advanced" and "retarded" fields. The idea you allude to by Wheeler is, of course, his self-excited universe. I attended one of his "Distinguished Lecture Series" lectures about it at the University of Louisville on 10 March 1980. He very kindly autographed my copy of his little book, "Gravitation".
@KSturtevant
@KSturtevant Жыл бұрын
Sabine, you are brilliant and entertaining. Keep up the great work.
@HakWilliams
@HakWilliams Жыл бұрын
You neglected to mention a reason for the apparent "pattern". I heard it is from phase shifts introduced photon entangler. (Or electron entangler). You end up with 180 degrees out of phase photons or spin-up and spin-down electrons. Is that right? So when you select just one going through a single slit you get a diffraction pattern that looks sort of like it an interference pattern but it's not. Is that right?
@piercingspear2922
@piercingspear2922 2 жыл бұрын
Physics need more people like you, Dr. Hossenfelder! :D
@nziom
@nziom 2 жыл бұрын
Agreed
@stephenrichards5386
@stephenrichards5386 2 жыл бұрын
Global warming needs more people like Sabine
@aniksamiurrahman6365
@aniksamiurrahman6365 2 жыл бұрын
Don't put her in a pedestal. Science communicators have to over-simplify and mystify anyway. Being a researcher herself, she's just able to find out other's gap and make a nice niche for her KZbin presence.
@mckanebullerlee3020
@mckanebullerlee3020 2 жыл бұрын
Understatement! She is gold. Academic community needs help!
@bonerici
@bonerici 2 жыл бұрын
There's only one Sabine
@TheDudeWithSome409
@TheDudeWithSome409 2 жыл бұрын
The old 'Obfuscated Science' A good way to sound brilliant while republishing someone else's work.
@jonasschmitt3548
@jonasschmitt3548 2 жыл бұрын
Great and for the first time in YT a complete explanation, thanks a lot for that!
@mapachem4828
@mapachem4828 10 ай бұрын
Thank you, I came from one of the other videos and I didn't make sense to me, I got stuck. This make sense, thank you for that beautiful explanation. Thank you.
@badbgp
@badbgp 2 жыл бұрын
Amazing vid and explanation! But why is the interference pattern at D3 & D4 not the same? Since they're both made from a mix of both slits would we not expect the patterns to be identical in position?
@lphillss5914
@lphillss5914 2 жыл бұрын
Same question here
@gehtdichnixan4704
@gehtdichnixan4704 Жыл бұрын
Why do we see interference with D3 and D4 at all? The photons at the screen cannot interfere! Is what she said. --- Edit: I found the answer in the article linked in the description of the video. It's all about quantum weirdness, but no magic is involved.
@yyyy-uv3po
@yyyy-uv3po Жыл бұрын
Isn't it because for each detector D3 and D4, one path gets 1 more reflection than the other, knowing that each reflection changes the phase by 180 degree ? I have some reminiscence of that, but would gladly accept a (dis)confirmation.
@afrosymphony8207
@afrosymphony8207 Жыл бұрын
@@gehtdichnixan4704 quantum weirdness IS magic!
@opstube
@opstube Жыл бұрын
isn't it intuitive to think that "sticking objects right in the path of something" (mirrors) does something? also when you have a look at how those "detection devices" actually work, it's not far off to imagine that stuff is filtered out in those measurements (for each device). the usual videos always show eyes or a camera being "outside" and just looking at everything, but they always omit those small details that Sabine showed here
@alanbloom20
@alanbloom20 2 жыл бұрын
Thank you for this video. I always couldn’t understand what was meant to be so strange about the quantum eraser experiment- it seemed obvious what would happen and thought it was just me that was missing something. Your explanation makes complete sense :-)
@slapmyfunkybass
@slapmyfunkybass 2 жыл бұрын
Maybe, but important to point out we’re still nine of the wiser on the double slit experiment itself. The video was debunking quantum eraser experiment.
@pet2226
@pet2226 Жыл бұрын
woww....so many great videos and explanations! I've watched PBS + Fermilab video of the quantum eraser + studied quantum mechanics at the university as an engineer but I've never got the essence of the quantum eraser in PBS + Fermilab....it led always to confusions. Now I know why....This explanation was really helpful! Danke schön for you and the team for this additional video..
@schmetterling4477
@schmetterling4477 Жыл бұрын
The essence of all of these videos is bullshit. ;-)
@pet2226
@pet2226 Жыл бұрын
@@schmetterling4477 hm. It is not clear what YT channels you are referring to. Do you mean PBS or Fermilab or Sabine's channel? I think however "bullshit" is too strong ...All of these channels are put a lot of effort in quality content creations and how to try to explain physics to a broad audience who have no background of high level math (eg high school students) .....
@terrysouth7201
@terrysouth7201 Жыл бұрын
Sabine, thank you for being the voice of reason and keeping us grounded in logic and common sense
@bloodswacky94
@bloodswacky94 2 жыл бұрын
Here is how I understand the weirdness of this experiment, which is in my view a little bit understated in this video: Assuming a single photon is emitted from the source travelling through the double slit. Then, following Sabine, either the blue path or the yellow path is taken, whereby these paths are decoherent. Now the wave function of the upper photon will look like a one slit diffraction pattern and hits the screen with the according probability at which point a second decoherence is taking place: Either the photon hits a crest of the "interference" pattern of D3 or of D4. This information is via "Einsteins spooky action at a distance" transferred to the second photon still travelling. Now the weird part: This means the second photon does not hit D3 and D4 with the same probability as the setup implies, instead it hits D3 with a greater probability if the photon was detected at a D3 crest and vice versa. If this is how the experiment actually works (I can't explain it otherwise), I would be greatly interested which state the second photon takes, such that the probability hitting the detector D3/D4 is no longer 50/50.
@willhastings731
@willhastings731 Жыл бұрын
Way late to this comment, but this is the same question I walked away with. Sabine simply stating that you can select a sample, just like picking pennies from a pile, doesn't explain how/why detectors 3 and 4 show this bias. This point can't be trivialized if the argument is meant to trivialize the "sending information back in time" perspective.
@DarthHydrae
@DarthHydrae Жыл бұрын
And I'm there later still, and find myself with the same question. Does someone has found some ressource that could clarify that, or is it beyond layman explanation?
@DavidByrden1
@DavidByrden1 11 ай бұрын
I explained this in a separate comment. But, to summarise it here: the mirror (that selects between D3 and D4) causes a 180 phase shift in the blue beam but not the yellow beam. That's just how mirrors work. So, you get 2 groups of photons with a 180 difference in how Blue relates to Yellow. Naturally they produce interference patterns that are 180 different.
@pedroproano4598
@pedroproano4598 9 ай бұрын
​@DavidByrden1 thank you for your answer, I am having the same question... Could you please refrence a more detail explanation on this mechanism?
@erinm9445
@erinm9445 6 ай бұрын
Late to the party! But this drove me so nuts myself, that I thought you might want an answer! The answer is that both entangled photons are in a superposition of two beams (one from left slit, and one from right slit), but as soon as the first photon hits the D0 screen the relative offset of the phases of those two photons becomes set. The relative offset correlates to locations on the D0 screen in a way that cycles from 0 to 180 degrees and back to 0, repeatedly as you move across the screen horizontally. Hence anything that is correlated with values for the relative phase differential of the superposition will take on that stripey pattern. The beam splitter does exactly that. It sorts photons based on wave amplitude, which is random for an ordinary photon, but which is nonrandom for a beam with a superposition of two phases with a *set* relative phase offset. Waves with certain relative offsets will have higher probabilities of going to D3 (and correspond with entangled photon twins that landed on certain stripes on the D0 screen), and waves with the other offsets will have higher probabilities of going to D4 (and correspond with the inverse stripes on the D0 screen, created by entangled twins). It's all explained beautifully in a new video on the delayed choice quantum eraser by a youtuber called Diego Emilio.
@artyomfomenko2232
@artyomfomenko2232 2 жыл бұрын
Haha, I actually remember how long I read the Wikipedia to understand these details and came to the same conclusion. Such a good feeling to be on the same page with Sabine :)
@odomobo
@odomobo 2 жыл бұрын
Same here!
@Cjeska
@Cjeska 2 жыл бұрын
Sure you did.
@CeezGeez
@CeezGeez 2 жыл бұрын
🧢
@AlexTorres-qv3hv
@AlexTorres-qv3hv 2 жыл бұрын
Then you read it wrong...there's no reason to deduct that graphs at d3/d4 actually overlaps....if you go over the mechanical description, the screen at D0 has a step motor that moves the screen only in one direction across the x axis....also there's no such thing as "being selective" the coincidence counter tells exactly how to pair the photons absorbed at d0 with those absorbed at d1d2d3d4
@localverse
@localverse 2 жыл бұрын
@@AlexTorres-qv3hv To confirm, are you saying Sabine's video is correct or incorrect?
@djschultz1970
@djschultz1970 Жыл бұрын
Matt, Kyle, John and Joe. I like this dynamic, Sabine. I think they do too. I am stuck quantum rewinding instead of quantum erasing. Sean Carroll is amazing.
@Cybjon
@Cybjon Жыл бұрын
THANK YOU! I've always wondered when reading about these experiments how they leaped to these conclusions and always thought there was something I was missing. Thought I'd been taking crazy pills.
@N7492
@N7492 2 жыл бұрын
Wonderful video! This healed my mind of a very troubling particles/photons-moving-backwards-in-time phenomena that the videos she mentioned had given me. Thanks, Sabine.
@JonnesTT
@JonnesTT 2 жыл бұрын
If there is one thing I love about your channel it's the statement "It's not as weird as you think". Because it always turns out not to be as weird as I've been told before.
@MrCmon113
@MrCmon113 10 ай бұрын
@@dextermorgan4490 Because that is nonsense. It's not "observed" and it doesn't change. Instead the particle, the measurement device and you all synchronize, such that all possible you's see corresponding particles.
@nitink9879
@nitink9879 3 ай бұрын
Summary: If the quantum eraser actually erased which way the photons went through, then D3 + D4 combined must be an interference pattern. But actually this isn't the case which means the quantum eraser didn't erase the information which way the photon went through. i.e., The quantum eraser didn't make the collapsed wave function return back to the superposition state.
@ramizr
@ramizr 2 жыл бұрын
thankyou a lot . I always wanted a perfect description about the Delayed Choice Quantum Eraser experiment but I always found different description in different places including websites like Wikipedia. TBH , I thought probably there's something fishy and that is what I found . All those KZbin videos and blogs were really misleading. As I studied more about it I kind of assumed that there's lack of communication in this description and also tried to email to some of the scientists but never got a reply haha . But , I'm really thankful to you.
@frede1905
@frede1905 2 жыл бұрын
Wow, this was very interesting to me. I too looked into videos about the delayed choice quantum eraser experiment a year or two back, and I too came to the realization that the results were all expected according to QM, no retrocausality needed, so long as you were careful with the quantum states of the photons, and what happened with those states once a photon had been detected at the screen. My thinking was heavily inspired by Sean Carroll's blog post that you mentioned in the video, and I was always confused about why seemingly nobody else was explaining this as well, especially PBS spacetime, who usually produce top-notch content. I think I was left assuming that I had misunderstood something, and I pretty much forgot about it. Now I am more sure of myself that I actually got it right.
@juzoli
@juzoli 2 жыл бұрын
“How many videos do you need of…” A lot more! This is a complicated subject, and it helps a lot by hearing multiple explanations, because all of these have a different angle. They complement each other, and I often understand it only after 3 or 4 such videos.
@boo6237
@boo6237 2 жыл бұрын
Agreed. even many available, admittedly this is one of the first to demystify it. Actually i have seen one "not so prominent" physicist explain this story before, but being ignored and overlooked by many as nonsense. A "Quantum Eraser" erases nothing! by Jeffrey H. Boyd MD Well, he is a MD afterall.
@juzoli
@juzoli 2 жыл бұрын
@@boo6237 To be fair, many other videos get to the same conclusion, that it doesn’t actually touch the past or anything like that. But they do it in such a complicated way that it is harder to understand. She has really cut the unnecessary information and made it simple.
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
*****HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!******* The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. All three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@saulberardo5826
@saulberardo5826 2 жыл бұрын
What part of the experiment setup determines which of the two non-overlapping interference patterns related to D3 and D4 end up shifted more to the left or to the right? Can we change the experiment in order to change how the patterns overlap? These might be minor points, but I'll register here my doubts anyway so I can think about this later
@schmetterling4477
@schmetterling4477 2 жыл бұрын
You can change the experiment any which way you like, but that won't change that you are really just chasing your own tail. The problems are not with the experiments, it's with how you are trying to describe the world. The world simply doesn't work that way.
@wiedreist6405
@wiedreist6405 10 ай бұрын
why can't I see the answer to this question?
@celebratedrazorworks6732
@celebratedrazorworks6732 Жыл бұрын
Wow, thank you so much! Validating a clear discrepancy for me. I could only discern that just half of the recombined information is being measured at either detector, however the revelation comes when you put the two patterns up and immediately it is noticeable.. Wow. Superb rationale.
@narfwhals7843
@narfwhals7843 2 жыл бұрын
If I remember correctly, Matt from PBS actually comes to the same conclusion, and explains the particular detector correlation in the followup video about the "winning the lottery with the quantum eraser" question. kzbin.info/www/bejne/aIbdqqeopNStapY
@meleardil
@meleardil 2 жыл бұрын
It sounds like a debunk, but it is NOT that simple. Because you do NOT change how you measure the "interfering - non-interfering" photons as it is done in the classical double slit... Nope! You change how you measure their entangled TWINS. If that measurement happens MUCH later, then the "interfering - non-interfering" measurement, than the conclusion is true that the effect of a decision seemingly propagates back in time. The fact that the 2 patterns can be combined into a non-interfering blob does not nullify the experience that the result of one measurement DO CHANGE based on the method of another measurement done LATER in time. If both detectors are working, the non-interfering blob can be seen, but the separate interference patterns can be "reconstructed" after post-correlating the measurement with the delayed measurement. This implies 2 things: 1. The entangled particles DO act in unison, which is very WEIRD 2. Einstein can rest in peace: information do not travel back in time, because the pattern can be restored by correlating the results of the 2 measurements. (this would mean that the entanglement is FTL, but the actual quantum information still obeys causality)
@cristianproust
@cristianproust 2 жыл бұрын
@@meleardil I love finding a real physicist in the comments. Good job 👍
@woowooNeedsFaith
@woowooNeedsFaith 2 жыл бұрын
I guess he did not reach quite same conclusion because of the nature of his comment on this same video: kzbin.info/www/bejne/iILZZnaMerF6abc&lc=UgzX3BUTGug1AR1pabp4AaABAg
@jamiegagnon6390
@jamiegagnon6390 2 жыл бұрын
See above where Matt actually admits he was wrong and says he is working on a video to fix it.
@rtyzxc
@rtyzxc 2 жыл бұрын
@@meleardil I'm very confused because these explanations are all so different from the traditional explanation, but if measurements do change based on another measurement later, it creates a paradox. You could create an ultra-delayed quantum eraser where you see the screen AND control whether to erase the which-way information later. Now, the system would either magically force your choice, or you could choose to get an impossible result (get interference pattern while also measuring which-way information). Another possibility would be that the mere possibility of this happening would create a clump pattern, which would all kinds of weird implications, it would become a reality predictor of "is it possible to press this button fast enough to enable collection of which-way information".
@HSMAdvisor
@HSMAdvisor 2 жыл бұрын
"Entangled particles are like a pair of brand-new socks. When you put a sock on your left foot, the other sock, no matter how far away will become the RIGHT sock!" - The analogies physicists use to explain entanglement without hidden variables :)
@ThePinkus
@ThePinkus 2 жыл бұрын
As long as You don't use incompatible observables You won't see a difference between entanglement and classical correlations (in measurements on separated systems). In fact, fixing the observable is equivalent to fixing a "slice" of classical logic within quantum logic. It is important to understand what is the same in quantum logic and classical logic, as much as it is important to understand what is different. That is why EPR and Bell use incompatible observables.
@matthewcahill4475
@matthewcahill4475 2 жыл бұрын
Sort of but not necessarily, let’s say that on the inside of the sock is an L or an R to denote which foot it goes on, you don’t know which is which until you check and when you see it is marked L, you know the other has to be marked right
@HSMAdvisor
@HSMAdvisor 2 жыл бұрын
@@matthewcahill4475 Your example, however literally has hidden variables.
@matthewcahill4475
@matthewcahill4475 2 жыл бұрын
@@HSMAdvisor well a simplified analogy will always lose detail it’s just a stepping stone to understanding, I just had to add the detail that you can’t choose the quantum state upon measurement you just know the other one when you do
@stevekiley6121
@stevekiley6121 2 жыл бұрын
What are the hidden variables? Where are the hidden variables? It is amazing how far mainstream scientisits will go to try and explain something which doesn't fit in with the mainstream (funny about Bohm though, he went well out of the mainstream, and believed in hidden variables).
@macronencer
@macronencer 11 ай бұрын
I might have to watch this one again! Or maybe five times. The funny thing is... throughout the video I kept thinking to myself, "these unintuitive paradoxes in quantum mechanics always seem to melt away when you think in Everettian terms..." - and then at the end, you recommended Sean Carroll's explanation :D I will definitely go and read his article too. I find it quite frustrating that I don't have the detailed physics knowledge to really explore these ideas, and yet I do have this intuitive conviction that all of the "weirdness" of quantum mechanics will one day turn out to be merely the confusion caused by our own quantum nature.
@solai
@solai Жыл бұрын
Finally someone to shed some photons on a much-abused quantum space! Thank you, Sabine! Please, never stop!
@MadScientist267
@MadScientist267 Жыл бұрын
Only just like everyone else, no actual demonstration. Just drawings and animations.
@TheDJRiffin
@TheDJRiffin 11 ай бұрын
@@MadScientist267 Yeh, while i love that she does not peddle the bs of other science quacks, a live demo would go a long way.
@augustadawber4378
@augustadawber4378 4 ай бұрын
@@TheDJRiffin Engaging in game of Semantics is not helping you. 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.
@TheDJRiffin
@TheDJRiffin 4 ай бұрын
@@augustadawber4378 John Wheeler sounds like a dreamer. Light is most likely the vibration of electrons. The energy passed from one electron to the next is what we currently call a photon. Let me know how this ages.
@johngough2958
@johngough2958 2 жыл бұрын
Or, as Feynman put it, there is only one mystery - remember what goes on in the two slit experiment, that's it!
@channel4me434
@channel4me434 2 жыл бұрын
Sabine, I think your reasoning misses the core idea of the original experiment done by Kim, Kulik, Shih and Scully in 1999. I see some principal differences: 1. you discuss the use of D1&D2 and D3&D4 separately, but the experiment is based on the combination of both. 2. you focus on what D0 (upper left) shows.(indeed a blurry blob, not surprizing when you combine 4 different patterns) rather than the flow of the photons. The original experiment shows that when a photon arrives at D0, it should decide whether it contributes to the interference pattern (wave) or to the two-bars pattern (particle). This depends on whether its counterpart photon is detected by D3/D4 or D1/D2 respectively, which happens 8 nsec later. This is done with the use of the coincidence counter (which you don't mention). And that's the baffling part: how does the first photon know in advance? You address the detector part of the experiment as total irrelevant, and indeed that goes for what is shown at D0 (your focus) but not for the puzzling result that the first photon acts 8 nsec earlier based on whether its counterpart releases their which-path information or not.
@WWLinkMasterX
@WWLinkMasterX 2 жыл бұрын
Good points, but isn't that curiosity inherent of any entanglement experiment, not unique to the "delayed-choice eraser" setup?
@folepi7995
@folepi7995 2 жыл бұрын
sabines point is you will never get a intereferrence pattern on the screen because of the BBO crystal. You could now afterwards split you photons into two parts. Using D1 and D2 you will not get so much information. But with D3 and D4 which are detectors which are dependent on the interferrence of the photons (position where they where emmitted at the crystal) you will get enough information two split it into two parts where their equivalent created an interferrence pattern. I think that was her idea. Its not contradicting what you said i guess
@OmateYayami
@OmateYayami 2 жыл бұрын
I am not sure if I get you right but the whole point of photon "deciding" is based on its wave function isn't it? If it's being detected by D1/D2 the counterpart at D0 is governed by a different wave function that when it's detected by D3/D4. It exactly the same as simple two slit pattern and selfinterference. How does a photon know whether it should interfere with itself and which wave function it's governed by? I think, currently it's accepted that it's given by the experiment setup, because how a single particle going through two slits at the same time would communicate if it's being detected or not at the other path. The act of detection in QM has it's problems with speed of light limits. How fast does the wave function change propagates? Isn't this the real problem here? Entanglement also has it's problems with light speed, spooky action at a distance is pretty well test, so to me it isn't surprising at all that if you combine into an experiment you'll get weird effects in that regard.
@channel4me434
@channel4me434 2 жыл бұрын
@@WWLinkMasterX It is unique to the "delayed-choice eraser" because only in this experiment time is involved. It suggests that a photon has to predict what will happen in the near future. Every other entanglement experiment is more about that as long as both entangled electrons are not interacting with something (e.g. a detector), they are in superposition which means that spin (and other properties) are not determined. As soon as one of the electrons is detected/measured, both electrons are forces to decide what the spin of each one is. This itself is weird enough when they are far away from each other: if the electron being measured decides to have spin left, the other electron must take spin left instantaneity, even if it is a billion km away. That's what Einstein calls "Spooky action at a distance".
@channel4me434
@channel4me434 2 жыл бұрын
@@folepi7995 If you put it that way you are right: our points of view doesn't conflict. But then I don't understand why Sabine calls her video ""Debunked", she does not refute the fact that the experiment suggest that photons caught by D0 must know in advance what the route is of their counterparts. And precisely that is the baffling part of the experiment and is not debunked.
@fabiantombers4966
@fabiantombers4966 Жыл бұрын
I remember we did the double slit eraser experiment in Highschool and I was so incredibly confused by this setup. thank you for explaining it so well!
@dosealas
@dosealas Жыл бұрын
To study the experiment at high school is amazing, which country are you in?
@fabiantombers4966
@fabiantombers4966 Жыл бұрын
@@dosealas this was in Germany right before graduating, one of the last things we did in our intro to quantum mechanics.
@bonelessbooks9263
@bonelessbooks9263 8 ай бұрын
@@fabiantombers4966Germany has a great history of physics. Einstein, Planck, and of course, Sabine Hossenfelder. I wish the same classes were offered in American high schools!!
@joseaca1010
@joseaca1010 Жыл бұрын
6 years ago, the PBS video on the quantum erased blew my mind, today you blew it again
@WylliamJudd
@WylliamJudd 2 жыл бұрын
I actually thought some of these videos that you mention already made this clear. Maybe I'm not understanding what it is they got wrong, but I remember them saying that you need the information in the present to know which particles to disregard and create the interference pattern in the past.
@WylliamJudd
@WylliamJudd Жыл бұрын
@@dextermorgan4490 the issue is that in order to observe something you actually have to interact with it, so when you add an instrument to detect which slit a photon goes through, you interact with the photon at the slit and cause the wavefunction to collapse. Exactly why and how wavefunctions collapse is still not well understood (as far as I know).
@PADARM
@PADARM 2 жыл бұрын
Finally! The fact that you are not afraid to debunk the videos of your colleagues speaks volumes of how much integrity you have as a Scientist. That's what science is about! Science is not about friendship, It's about the truth. Congrats Sabine!
@donniseltzer7718
@donniseltzer7718 2 жыл бұрын
IKR. Sabine Rocks!
@TheBrightmanFan
@TheBrightmanFan 2 жыл бұрын
That's what I love about her
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
*****HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!******* The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. All three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
***HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!****** The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. The The three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.”
@theshermantanker7043
@theshermantanker7043 Жыл бұрын
She's all fine and good until it's her theories that are on the line. You'll see a different side of her when that happens
@somebodysomewhere5571
@somebodysomewhere5571 2 жыл бұрын
The version of the experiment you present wasn’t the original one done in 1999 it’s a almost completely different experiment
@infinitinifni7057
@infinitinifni7057 2 жыл бұрын
I am the /ˈrīdər/ you manifested earlier this year with your hypothetical comment about the starting state of the verse, and I approve of this message. Once again you have corrected yet another misunderstood then mystificated measurement and corrected mass conceptualization of it's contextual implications. Your work is noted. Thank you so much.
@franks.6547
@franks.6547 2 жыл бұрын
So how do the photons get reshuffeled into D3 and D4 in just the right way to make their counterparts reveil an interference pattern that was neither in the blue or yellow track? How does the half-mirror preserve the correlation with the partner-photons in the blurry pattern when it is randomly chosing D3 and D4?
@jjhhandk3974
@jjhhandk3974 2 жыл бұрын
She honestly just doesn’t understand the experiment at all. I’ve never seen anyone get this more wrong
@folepi7995
@folepi7995 2 жыл бұрын
unfortunately Sabine left out this part... my guess: The photons at D3 and D4 interferre as well. And when you look at interferrence in a more traditional way with lines (Huygens style), you see that the position and angle of the photons emmited by the BBO crystal is decisive attribute to determine constructive or destructive intefference. The positions are the same and the angles are probably linked (e.g. always 90degrees) for the photon pairs emmitted by the crystal. So when the photon pair shows constructive interferrence on the screen, they show constructive or destructive interferrence and D3 or D4 and vise versa. Sorry for my english. Just take it as a guess. But this is what came to my mind.
@franks.6547
@franks.6547 2 жыл бұрын
@@folepi7995 Thank you, that makes sense to me! That way, it is a little bit less mysterious: one only delays the choice of either looking at which-way or interference - simultaneously in the near and in the far branch, which both somehow share the same "quantum information". And it probably doesn't matter if the geometry in the far branch is comparable. It just matters, that some blue and yellow track photons land on the same spot (detector, e.g. D3) in the far branch. All events formed on that far spot D3 have partner events in the near branch where yellow and blue track combine on the screen. These near events form a coherent pattern according to the particular near geometry. But they take part in such a coherent pattern if and only their correlated far branch events stem from a blue/yellow superposition in whatever pattern that far branch geometry allows for. So, the actual geometric pattern is less important than which photons to include: Blue/yellow superposition photons form interference patterns in the near and in the far branch. But photons that are "forced to appear/measured" in an insolated blue or yellow track (like D1, D2) in the far branch have only pure blue or yellow partners in the near branch. That means actually, whether you regard a near branch screen photon as mixed yellow/blue or as pure blue or yellow track photon is not objective. You reassign them according to whatever type of photon events you force to appear as their partners in the far branch (mixed or pure). The correlation between the partners is spread out space-like anyway, so no-one should expect a fixed time order anyway.. just rambling here... thanks again!
@roflistganztoll
@roflistganztoll 2 жыл бұрын
@@jjhhandk3974 can you elaborate what she got wrong?
@kdowey13
@kdowey13 2 жыл бұрын
​@@roflistganztoll She did not characterize the experiment properly-- it was a thoughtfully crafted experiment that did indeed erase which-path information. See this short vid, without narration it explains the part Sabine is mischaracterizing: kzbin.info/www/bejne/hmPGfnmojdaVj68 D1,2,3+4 are in operation simultaneously. D0 detector (supposed to be the same as the reference "screen" in the upper left in Sabine's video) correlates each entangled photon pair *in time* (time is tracked for each detector). By tracking each photon's arrival at the detector in time, we see that on D0 (the reference "screen") the photons that arrive either demonstrate single-slit (known path) or interference (unknown path) patterns, based on the *random* path that photon's entangled partner traveled through. This is the strange part, because the only opportunity for the original photon to self-interfere is at the double-slit, which is at the very beginning of the process. Her debunking boils down to the notion that there is "selective disregarding" between D3 and D4, but this doesn't make sense as @Frank S pointed out with the question: why are there distinct peaks and troughs (interference pattern) at D3 and D4 when the half-mirror is supposed to randomize the photon paths? Simply adding together D3 and D4 does not explain why an interference pattern was preserved on both of them. If anything, the fact that D3 and D4 patterns align begs an even stranger question about the trajectories of an unconnected string of individuals photon in relation to a half silvered mirror. @Fol Epi makes a fine attempt at explaining, but it breaks down and cannot answer Frank's question when you think of single photons passing through the system. The time-defying weirdness of this experiment that "everyone" has been talking about remains intact, and this is shown if you understand the video linked above. Cheers
@ThatCrazyKid0007
@ThatCrazyKid0007 2 жыл бұрын
This experiment fascinated me the most for the last two years or so, I never bought into the retro causality but I definitely thought there was more to the experiment than what you've explained here. Seeing it demystified like this is exactly why I love your work Sabine, you just get straight to the point and explain it in a way that's easy to digest, thank you.
2 жыл бұрын
Same here, this video freed me.
@DmitryShevkoplyas
@DmitryShevkoplyas Жыл бұрын
Had to watch this many times! Brilliant! Thank you!
@paulkocyla1343
@paulkocyla1343 Жыл бұрын
I´m a bit confused. You say that the pattern on the screen will always be the blob and never an interference pattern. But at 7:30 you show that it changes, depending on what you do on the far side. And this WOULD imply a retro-temporal action. Or did I misunderstand something? Is D0 always showing the same pattern, no matter what happens on the far side?
@leogama3422
@leogama3422 2 жыл бұрын
Thank you, Sabina! These experiments and explanations were driving me crazy. Quantum physics has enough weirdness even without past-changing phenomena
@AaronKarper
@AaronKarper 2 жыл бұрын
Thank you so much Sabine, the big blob instead of two blobs was exactly what I needed
@mecmeuf4528
@mecmeuf4528 2 жыл бұрын
lmao for sure
@alwaysdisputin9930
@alwaysdisputin9930 2 жыл бұрын
lol
@carrson161
@carrson161 2 жыл бұрын
I hate to be the bearer of bad news because I understand that wave-particle duality is hard to wrap your head around, but Sabine is flat out wrong. You DO get two blobs when you put detectors behind the slits in a double slit experiment -- that result is quite literally the basis for wave-particle duality and one of the foundations on which our understanding of quantum mechanics is built. There are literally thousands of experiments that show this to be the case. This isn't a question of interpretation, this is experimental fact. Sabine cited literally ZERO experimental results, papers etc. that show you get a single blob and not two. Extraordinary claims require extraordinary evidence --- the data and results of double slit experiments have been experimentally verified thousands of times. The data is the data -- Sabine suddenly claiming you get different data when you perform a double slit experiment is just wrong -- and to make a claim like that and cite zero evidence or papers to back up such a claim is an incredibly dangerous thing for a science educator to the public to do. Its making tons of commenters like yourself suddenly question what they've heard/known about quantum mechanics because shes a well known and respected physicist. I cannot for the life of me understand why she would claim something like this which can be proven to be factually wrong. Its like saying you get ice when you light a match, not fire. Its literally blowing my mind she would claim this.
@christianlibertarian5488
@christianlibertarian5488 2 жыл бұрын
Double plus good on ya' for this one.
@alwaysdisputin9930
@alwaysdisputin9930 2 жыл бұрын
@@carrson161 Can it "be proven to be factually wrong"? any video of 2 blobs?
@science6213
@science6213 Жыл бұрын
This is very educational! I now understand that if we combine D3 and D4 we get the same pattern as D1 + D2, but what happens if conversely we separate out the particles from graph D1+D2? Will individual D1 particles now create a lined pattern or will it remain distributed?
@DavidByrden1
@DavidByrden1 11 ай бұрын
No, it won't make a difference. In fact we don't even need to have both D1 and D2. Either one of them, in theory, is sufficient to imply which way the photon travelled. But in a real experiment we need them both to eliminate fake hits caused by noise in the detector screen.
@leeds48
@leeds48 10 ай бұрын
@@DavidByrden1 And this is an example of why the observer effect can't be about disturbing the system via equipment, etc. The mere implication/inference of what happened at the other slit will accomplish the effect rather needing to actually measure at the other slit.
@alexmipego
@alexmipego 8 ай бұрын
I've been thinking about this and couldn't the answer be actually very simple? A wave is formed when the particle is created, observation which implies particle/field contact takes a nano second, but the wave still goes on… henceforth the particle keeps moving but now it's not following the wave.
@beanieteamie7435
@beanieteamie7435 2 жыл бұрын
This why I am much more interestes in having the crystal *BEFORE* the double slit. A beam of individual photons is split into entangled pairs, entangled photon 1 goes into the double slit, number 2 goes in a different direction and travels further to preserve it longer. Number 2 then hits a beam splitter that either sends it to be measured, or a place where we don't measure it at all. If number 2 is measured, the entangled pair collapses. And no longer acting like a wave, no interference can happen. Please correct my understanding if I am wrong.
@DrDeuteron
@DrDeuteron 2 жыл бұрын
1 goes into a YDSE and interferes. How are 2's two paths supposed to change that?
@beanieteamie7435
@beanieteamie7435 2 жыл бұрын
@@DrDeuteron Because the photons are entangeled, you reveal information about photon 1 when you measure photon 2. See it like this, if write 1 on a sheet of paper, and 2 on an identical piece of paper. Ask someone to shuffle them. Then light one on fire. You will still know which number was set on fire when you flip over the other one. Whenever you observe (gain information) about a photon it collapses and acts like a particle. And a particle cannot interfere with itself. And as this information reveals something about the past, and the outcome of the past is dependent on the information you have. It would seem like what happens in the future is able to interact with the past. Now this doesn't nessecary mean you are able to change the course of time. Maybe it was always bound to happen anyway?
@DrDeuteron
@DrDeuteron 2 жыл бұрын
@@beanieteamie7435 I think you missed the point of the video. It's always a wave. What you need to focus on is all the ways to get from the initial state to the final state. If there is more than 1, you need to add up the amplitudes FIRST, and the ||x||^2 them to get a probability. That's it, all quantum woo is contained therein.
@aliceinwonderland887
@aliceinwonderland887 Жыл бұрын
Really? ***HOSSENFELDER HAS BEEN DEBUNKED****NOBEL PRIZE 2022 PROVES NON LOCALITY IS REAL!****** The trio’s experiments proved that connections between quantum particles were not down to local ‘hidden variables’, unknown factors that invisibly tie the two outcomes together. Instead, the phenomenon comes from a genuine association in which manipulating one quantum object affects another far away. German physicist Albert Einstein famously called the phenomenon ‘spooky action at a distance’ - it is now known as quantum entanglement. The The three winners are pioneers of the fields of quantum information and quantum communications, says Pan Jianwei, a physicist at the University of Science and Technology of China in Hefei who participated in some of Zeilinger’s landmark experiments as a graduate student in the 1990s. The recognition was long overdue, Pan says. “We have been waiting for this for a very, very long time.” What now Sabine?
@francescocannistra7915
@francescocannistra7915 2 жыл бұрын
@Sabine Hossenfelder, I am afraid you didn’t get it right this time. What you say is partially correct: indeed you can select subsets of dots on the screen arbitrarily in order to create whatever pattern you want. However, in this case, 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. Rather it’s exactly the way around. The subsets of dots are not selected arbitrarily to show target patterns: on the contrary, dots 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 resolved) some patterns do emerge and from other properties (photons with which-path still unresolved) 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, I believe you are wrong in minimizing the meaning of the experiment. On the contrary, I believe that the experiment really shows what is claimed in the main descriptions that can be found in the literature (and on KZbin) that, instead, you contest: • The dots originated by photons that were subjected to a which-path measurement formed a smoothed-out distribution on the screen regardless of the fact that at the time they hit the screen they could still skip the which-path measurement. • The dots originated by photons that were not subjected to a which-path measurement formed an interference pattern on the screen regardless of the fact that at the time they hit the screen they could still undergo a which-path measurement. In other words, it's like if at the time they hit the screen they had already incorporated in the dynamic properties the info on an event that indeed would have happened later (i.e. undergoing or not a measurement of the which-path info), What this means then it’s 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 that this 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).
@Azrael1486
@Azrael1486 2 жыл бұрын
It's amazing that so many creators are willing to chat in the comments... Except for skeptic scientists. They never address good rebuttals like this... Because you're right.
@francescocannistra7915
@francescocannistra7915 2 жыл бұрын
@@Azrael1486 thanks. Not sure I am right but I think at least that my argument is well grounded upon logics.
@scottg5467
@scottg5467 Жыл бұрын
Sabine, would you consider doing a video on the box-pair experiment? I read about it a long time ago in a book called The Quantum Enigma, by Bruce Rosenblum and Fred Kuttner. I always wanted to know if anyone had repeated the experiment but with additional semi-transparent mirrors, if that were even possible. Seems to me that with the additional mirrors, if there were some physical component to the wave function of light, then the probability of collapse would decrease the further away from the intial mirror. But, if there truly is no physical property associated with the wave function, then the furthest box would have the exact same probability of collapse as the first one. The other explanation is that I don't know what I'm talking about. If I understand Occam's razor, then that's the most likely explanation.
@OrbitTheSun
@OrbitTheSun 2 жыл бұрын
One thought: Could it be that the pattern on the upper screen is the main maximum of a double-slit interference image and that the secondary maxima do not appear on the screen because they are outside the measuring range of D0? That would explain why no interference minima can be seen in the pattern.
@somethingsinlife5600
@somethingsinlife5600 2 жыл бұрын
My thoughts for long time on the Delayed Choice Quantum Eraser experiment have been like this "Sounds too much like magic, can't be true or we are doing something wrong". And I hate that everyone jumps on the opportunity to make it sound like magic, everyone makes the "Look" vs "No look" sound like magic as well.
@ThingsYoudontwanttohear
@ThingsYoudontwanttohear 2 жыл бұрын
I had the same thoughts. Another thing that made no sense to me is this: Extrapolating from the double slit experiment that our consciousness somehow determines reality, because when you "look" at a foton the interacting wave pattern disappears.....but you cannot just 'look' at a foton. It literally has to hit you it the eye for you to register it. At quantum sizes everything that is measured is interacted with. (Influenced or even stopped dead in its tracks) As far as I understand this rule also applies to the censors used in these experiments. So the foton censors interact with the fotons that they measure. This does not sound like the magic of consciousness to me, but more like physically bumping into waves/particles.
@freshbakedclips4659
@freshbakedclips4659 2 жыл бұрын
@@ThingsYoudontwanttohear waves become particle or particles become waves, doesn't it sounds more magic to you?
@ThingsYoudontwanttohear
@ThingsYoudontwanttohear 2 жыл бұрын
@@freshbakedclips4659 If you put like that, then yes indeed, that sounds like magic too.
@frozen_eclipse
@frozen_eclipse 2 жыл бұрын
The result of the experiment is still influenced by the future. It is still magical.
@angrymokyuu1951
@angrymokyuu1951 2 жыл бұрын
​@@frozen_eclipse The screen is merely a fifth detector. It detecting(interacting) with photons before the labelled detectors do the entangled ones just means it's the bit collapsing the wave function/entanglement.
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