A Real Life Quantum Delayed Choice Experiment

[@arminahnoud9068]

When you don't see an interference pattern it doesn't mean light photons are not behaving like a wave. It just means there's no interfering wave because there's only one path.

[@muffininacup4060]

Doesnt even have to be one path, the interference is due to the two waves being misaligned, not due to the existance of two waves by themselves

[@deepshabad]

You made that sound easy. Thank you. I think you nailed it.

[@SpaceMan-f6d]

Exactly!

[@armangevorkyan1975]

It reminds me the joke where scintist doing experiment. He cutting insects one leg an then making noise, the insect is start running. After that he cuts another leg, then make noise and the insect does running. The scintist repeat the cutting the legs of insect until he cuts the last one, and then after making noise the insect does not running. The conclusion that scintist did, is that insect without legs does not hear:) Good experiment, interpretation could be more.

[@Statin-blood_cholesterol_lower]

😂

[@andrejburcev6023]

😆

[@2nd-place]

Action Lab in 10 years: So I created a Time Machine but it can only send messages back in time that don’t change the timeline.

[@Jay_Kay666]

"Sorry, I'm late from the party. Come and meet me in the future?"

[@grapehool]

D-mail?

[@nickduplaga507]

Which timeline won’t change? Past, present, or future (universe branch)? Many Worlds Interpretation of Quantum Mechanics fixes the paradox.

[@AM-jx3zf]

well 9 years left

[@milkwater1204]

FG No. 8: Phonewave (name subject to change)...

[@chrishbeatboxing2291]

Yooo i remember learning this in my quantum mechanics class. Literally blew my mind

[@jamessidis4298]

LoL

[@lotsoffreetime8392]

What happened to your brain matter after that happened 🤔

[@chrishbeatboxing2291]

@@lotsoffreetime8392 it blew even harder after i had to write two 2000 words paper on different interpretations of quantum mechanics + the quantum erasor

[@mickyr171]

@@chrishbeatboxing2291 My guess is, you didn't pass the class, or did you?, we cant know until you show proof of the certificate

[@lotsoffreetime8392]

@@chrishbeatboxing2291 after reading your comment i lose some of brain cell 🙃

[@JNCressey]

Even without the second beam splitter, the light still goes into a superposition of taking the red path and the blue path. A wave with half amplitude hitting the detector doesn't mean it would try to produce half a photon, it still produces a whole photon but only has half probably of doing so. Detecting photons at the detector doesn't mean they must have traveled as particles. The beam splitter still splits the photon into a superposition of going either way, and half of the photons end up hitting where that side-beam is pointing and don't hit your detector.

[@rotorblade9508]

yes, the explanation seems hard to accept because it makes you think there is instant action at a distance, but it just works

[@jonaohana3376]

Yeah most def the left atoms quark nuetron start def will lead to orange juice

[@JNCressey]

@Bobby T, in the double-slit experiment, particles are detected on the screen. Are you saying that means they travelled as particles even when producing interference patterns?

[@JNCressey]

@Bobby T, if it had to be a particle some amount of time before hitting the screen, wouldn't that change the pattern? is the diffraction pattern on the screen not consistent with it travelling as a wave all the way up to the screen?

[@JNCressey]

@Bobby T, if they travelled along straight trajectories, wouldn't there be a shadow in the middle because of where there is opaque between the two slits?

[@arslongavitabrebis]

The destructive interference pattern comes when the wave function of the to beams of light are split, dis-aligned and recombined. The beams of light behave like a wave function all the time.

[@Mr.BobsDog]

@@InstagramUser2 you wish jelly fish

[@joaofelipecamargopinheiro4230]

Exactly, but Quantum mechanics is open to interpretation. Even though they all agree on the predicted outcome of experiments, they disagree on what the wave function represents. And then you get, in my point of view, ridiculous interpretations, like the one presented on the video or many-worlds interpretation.

[@DaP84]

So why does the interference pattern appear in the double slit experiment, even when shooting separate particles, one by one?

[@joaofelipecamargopinheiro4230]

@@DaP84 It's the same reason. The particles behave as wave functions, I mean each particle individually so it doesn't matter if it's one at a time or one billion at a time, and this wave function, for each particle, spreads over all space. You could imagine It like a water wave, even though they don't behave exactly the same. So this wave function interferes with it self, causing the interference patterns, the analogy with other types of waves here is basically perfect. I don't think anyone disagrees with what I just said, but the problem is: "what does the wave function represent ?". Roughly speaking, the answers to this question are called interpretations. The most popular one is the Copenhagen interpretation, where the wave function represents an amplitude of probability, but there are many many others. A very interesting one is the de Broglie-Bohm interpretation.Truth is that it doesn't really matter, since they all agree on the outcome of the experiment and can't be tested, but it's interesting conversation

[@jamiebaxter9360]

@@joaofelipecamargopinheiro4230 exactly. Why do people always make it sound more complex than it is?

[@JaroslawFiliochowski]

Adding/removing the second beamsplitter doesn't change how the photons travel. With a second beamsplitter: both red and blue path reach the beamsplitter, get split, and in both directions a mix of 50% red + 50% blue comes out, so when one reaches the target, there is an interference pattern between them both when they excite electrons in the target, making them emit "reflected" photons. Without a second beamsplitter: only one path (red or blue) reaches the target, and has nothing else to interfere with.

[@RomanPawleta]

True

[@honeyxm8]

I've heard about this several times, but it's really cool to se a real life experiment of it!

[@marcin4xm]

where do you see real life experiment ? any single foton emiter ? any foton detector ?What about 1000 kilometer long photon of 300hz frequency ?

[@1998ichigokurosaki98]

@Eric C pseudo intellectual detected. Do u even realize that the point is to use 1 photon because it cant take 2 paths at the same time? If u have more than 1 than each of them can take different path

[@kermitthedarkness1388]

@@InstagramUser2 I'm better than Instagram User, My content is better fr

[@thehulkamaniabrother2.089]

Have you ever heard of Breaklife???

[@thehulkamaniabrother2.089]

@@kermitthedarkness1388 I'll make sure I see you down here at Breaklife!!!

[@mduvigneaud]

I'm not sure your explanation is quite right: without the second beam splitter your setup is just detecting that the photon traversed the blue path, not if it's a particle or wave. I think you might have mixed that this with adding polarizers in the paths after the first beam splitter to detect which path was traversed.

[@Tore_Lund]

I'm not sure either that this gives any meaningful result in air, it has to be done in a vacuum. I suspect this experiment is an explanation model, not indented to be used to test anything.

[@mduvigneaud]

@@Tore_Lund As far as I understand it's equally valid in air as in vacuum. The experiment is to test if photons are particles or waves (spoiler: they're ALWAYS waves, even when you measure them as particles.) The problem with removing the second beam splitter is that it doesn't tell you that it's NOT a wave and only transited one path as a discreet particle. It only tells you that it DID transit the blue path.

[@Tore_Lund]

@@mduvigneaud Air does interact with photons, there is diffraction which means that the are absorbed and reemitted. However as the distance is short, the majority of photons might not interact with any air molecules?

[@mduvigneaud]

@@Tore_Lund From what I understand that's a bit of a misconception: they aren't absorbed and re-emitted. They're diffracted because they are waves. The interaction with air molecules is also not relevant to trying to determine if they are particles or waves.

[@Tore_Lund]

@@mduvigneaud It depends of the molecule; like with spectrography, specific wavelengths are absorbed and reemitted, in this case, green might be be able to pass through, but if there is an interaction, the result is the same as when the light hits the screen, the wave function collapses before it ever reaches the screen.

[@lavasharkandboygirl9716]

“A simplified diagram looks like this” *proceeds to show literal wizardry on screen and call it simple*

[@jpe1]

Superdeterminism is another way to explain the retrocausality seen in this experiment. In a superdeterministic universe the photon either propagates as a wave (when the 2nd splitter is in place) or as a particle (when the 2nd splitter is removed) because the future placement of the splitter is already determined.

[@dunga.]

If you add the beam splitter, you simply can't tell which photon went which way. The interference pattern is one half of the sum of the photons seen without the beam splitter. You just can't tell which beam it is. When both interference patterns are combined they show the same image as without the beam splitter. There is no going back in time, sorry folks.

[@EYYEofficial]

d semip reflective mirror pattern is causing this, especially or in this case mainly noticable when added up a 2nd time enhanced. So this is not that wavy as said to be. In general, all only exist as particles, waves are just the connection between those depending on the state. Just like here electromangetic particlelike. So almost an optical illusion causing this to appear differently, as the pattern has a certain sum threshhold for the perception at this distance to be seen. But there is no spooky thing going on, just a threshhold

[@Veptis]

The follow up Huygens optics videos cleared it up for me. Single photon levels are a misconception

[@steadfasttherenowned2460]

I have a vintage beam splitter Prism from an atmospheric mass spectrometer my grandfather designed and built with his team in the early 1970s. I have all the mirrors and lenses from the original device too. It was used to measure diffrent gasses in the earth's atmosphere. I only have the optical parts for it though. I don't know what happend to the rest of the original machine. I do, however, have the original manual and the pamphlet that gives a brief description along with credit to the team who built it aswell as photographs. It's pretty sweet.

[@williamcrosby1061]

Look further into this. He did not fully describe the retrocausal effect probably because it's very nuanced. The people who first performed the quantum eraser experiment call it "causally disconnected" this is inclusive of instantaneous action at a distance aswell as retrocausal effects. Its important to note no information can be sent back in time but you can observe the effect after sending alot of individual photons through.

[@lucbloom]

So I’m not the only one who felt like this could have been explained better? Mind you, still grateful for the otherwise excellent and free videos! :-)

[@williamcrosby1061]

@@lucbloom just look up "john wheeler" on youtube the first video should be a 2 min video of him talking about the delayed choice. He puts it in plain English.

[@goldenalt3166]

@@williamcrosby1061 I find the videos putting it in layman's terms make it sound more magical than it appears to actually be.

[@williamcrosby1061]

@@goldenalt3166 right... because retrocausality is very non magical... you obviously didn't watch john wheelers video either or you definitely would not have said that.

[@renedekker9806]

@@williamcrosby1061 _"just look up "john wheeler" on youtube"_ - I did that. The video does not make it very clear at all. _"because retrocausality is very non magical"_ - no retro-causality is necessary, unlike Wheeler seems to imply.

[@MrOvipare]

To understand why the delayed choice quantum eraser does not imply time travel (or retrocausality), I recommend Arvin Ash's video on it. Sabine Hossenfelder also did a video on the subject. In the defense of The Action Lab, which often makes great videos, this is a very technical and tricky subject.

[@markfernee3842]

This is not the delayed choice quantum eraser, but rather Wheeler's delayed choice experiment. The retro-causal nature of the experiment depends on there being a choice in the first place. The phenomenon being explored here is called "contextuality". That means the measurement itself determines the property of the quantum object being detected. This is a central property of quantum theory.

[@РаисаСафарьян]

пока что нет правил запрета передавать информацию во времени обратно!)))) биткоин в помощь!)))

[@tobystewart4403]

When we detect a "photon", we are actually measuring the change in energy state of an electron. This electron is local to the measurement device, it has not moved. The wave in the electric field has caused the local electron to change energy state. If we wish to be esoteric, we can argue that a "particle" is anything that transports energy, and so fluctuations in electrostatic force (i.e. waves in the electric field) can become "particles". However, this is our choice of perverse use of language, not some profound condition of reality. The reason i say it is "perverse use of language" is because the word "particle" already has a pretty well understood definition. It means a substantive thing, occupying 3 dimensions of space, having mass, and being capable of exuding force, whether that force is gravity from mass or electrostatic force, as charge. Now it's important to note that this perversity is not limited to the layman's use of everyday terminology. It's perverse with regard to Maxwell's laws of electromagnetism. Maxwell has it that there is an absolute distinction between, on the one hand, a "thing" that occupies space and 3 dimensions, and which exudes force such as charge, and, on the other hand, a mere fluctuation in the strength of a force field that is exuded by a substantive "thing". Maxwell called the movement of the former a "current", and said that this movement creates a magnetic field. He stated that the movement of the other, a mere wave in the field, did not create a magnetic field, and was not affected by a magnetic field. Indeed, it was Faraday who first established this fundamental difference between moving waves in an electric field and moving charge carries in space. The former is light, the later is current. Describing light as a "particle", therefore, contradicts Maxwell's laws, and has it that light waves are actually currents, carrying a source of charge across space. This is manifestly not so, and thus we might begin to question why the issue of light being a "particle" is so culturally resistant to disproof. Perhaps some people are just particle folk, to the very end, and cannot abide a world view that contains such things as "waves". Waves are pretty strange. It's almost as if they transport pure information across space and time, existing as metaphysical messengers in a physical world. If waves are not magic, they will do until the magic gets here.

[@arifbagusprakoso2308]

Wow... how can I miss this core concept during college!?

[@dineshvyas]

A well known fact but never it had been stated so beautifully. Amazing.

[@simengfu7352]

You make physics enjoyable like art.

[@JohnTan]

Light is both wave and particle. Wave-only explanation fails to explain photoelectric effect, especially the threshold frequency part.

[@tobystewart4403]

@@JohnTan You are making the absolute declaration that the photoelectric effect is proof of the existence of particles. So, you claim that the photoelectric effect is evidence of a 3 dimensional substance, travelling across space and time, and itself occupying space and mass. A "particle" of matter. OK, so what is the photoelectric effect? The photoelectric effect is the phenomena of electrons changing energy state by quantised steps, and not according to an infinitely variable scale. When electrons change energy state, either absorbing or emitting energy, they do so in strictly quantised amounts. Why do we believe that this behaviour is associated with particles? Well, it can be. If we take a bullet with a known mass, and we shoot it with a known velocity at another object, we can calculate the kinetic energy in imparts to the other object. Both bullet and object are "particles", in effect. So, by using a kinetic model of energy, where mass and velocity are deterministic of all reality, we can understand "particles" as capable of transporting energy across space, and exchanging energy with other particles. This is why we suppose that the photoelectric effect might be the result of particle interaction. It fits the kinetic energy model of the universe. Yet, it is demonstrably wrong to declare that all exchange of energy in quantised form involves the interaction of particles. Consider the humble raindrop, and phase change. Water vapour condenses into droplets, each droplet representing a quantised amount of energy. That is to say, it takes an exact and quantised amount of energy to make one droplet of a given size from water vapour. Even though we understand that many millions of water molecules are combining to give each single quanta of energy emitted by the condensation of each individual rain drop, we describe the cumulative effect of all these molecules as a single quanta of energy, that being equal to one raindrop. And this is, in fact, a quantised event. Each droplet actually exists, and each droplet really does have it's own "quanta" of energy that dictates it's state, as either a liquid or a gas. And thus, every droplet of water has it's own "photon" particle, if we accept that quantised exhibitions of energy are hard proof of particles that transport this energy exchange. It's rather magical a mysterious, the way phase change between gas and liquid exhibits apparently arbitrary examples of quantised energy. Even so, for the purposes of the discussion of light, we have now established that water droplets must have particles associated with them, particles that hit water vapour and cause it to change energy state. Why? Well, we've established that any quantised exhibition of energy exchange is hard proof of the existence of particles, objects with 3 dimensions and mass and so on, carrying this quanta of energy from one place to another place. Therefore, as we have raindrops occurring, we have proved that raindrop photons must exist, and thus there must be these particles, with specific size and mass, capable of exchanging the energy needed to vaporise and condense water droplets. We are not permitted to argue that phase change occurs due to temperature and pressure. No, we have a quantised exhibition of energy, and we have declared that such a thing is hard proof of particles that transport the whole sum of this quanta of energy as kinetic energy. Now, a thoughtful person might try to argue that a change in temperature causes the droplet to form (or to disappear) because many "photons" of energy are being exchange by molecules. This argument does not explain why, or how, many small particles can suddenly exhibit the behaviour of one single large particle, but even so it does bring us back to discussions of particles being the carriers of energy, to and fro, and so it cements the idea that where we see energy exchange, we see particles hitting each other. Yet, what if we cause the phase change and water droplets formation by changing pressure only? How does the interaction of particles now explain the quantised change in energy state? A change in pressure doesn't even involve the exchange of many photons. Suddenly, we are faced with quantised exhibitions of energy exchange, without any apparent interaction of kinetic energy between particles. The point here is that "quanta" of energy, or discreet packets of energy, are analogous to the exchange of kinetic energy between particles of known mass, but they are hardly proof of such things. Yes, it is true, when we examine particles in the world, we can observe quantised transfers of energy. It is a bold claim, however, to argue that every quantised exchange of energy is hard proof of one particle striking another. This desire to perceive the world as substantive objects striking other substantive objects, this article of faith in the kinetic reality of things, is very ancient. Newton was criticised for suggesting the existence of gravity, because gravity violates the idea of a mechanical universe, a place where all things touch other things, and all exchange of energy is always kinetic. So does electrostatic force, but gravity violated the mechanical universe worldview long before electrostatic force did so. Anyway, that's what I think about that. I don't think one can convince the hard core particle people. Those folks are extremists. They are beyond reason. The believe in neutrons, and pineapple on pizza, and every other kind of perversion and wickedness. We just have to make the sign of the cross when folks get their particle fever on, and say "There, but for the grace of god, go I."

[@Chrisiskewl100]

thats not really the delayed choice experiment. That involves a special crystal, called a non-linear BBO crystal, that actually does split the photon into 2 entangled photons each with half the energy of the initial photon, and it is also a continuation of the double slit experiment, so you would need that in there as well.

[@jamesedgewood4643]

You're talking about a different experiment. The Delayed Choice Quantum Eraser experiment. This one is the Wheeler Delayed Choice experiment.

[@EYYEofficial]

d semip reflective mirror pattern is causing this, especially or in this case mainly noticable when added up a 2nd time enhanced. So this is not that wavy as said to be. In general, all only exist as particles, waves are just the connection between those depending on the state. Just like here electromangetic particlelike. So almost an optical illusion causing this to appear differently, as the pattern has a certain sum threshhold for the perception at this distance to be seen. But there is no spooky thing going on, just a threshhold

[@Sharperthanu1]

Wheeler's Delayed Choice is usually not done with light.It's done with electrons and full atoms.

[@MatviiCheked]

on 3:10 why whole piece of light "photon" can't divide into two smaller pieces of light? Then when you have the second beam splitter they interfere with each other, and when you remove the beam splitter, only one "small piece" gets there, and the other one passes in the other direction.

[@pn2543]

plot twist: from the pov of light, there is no paradox, since there is no time

[@mr.loveandkindness3014]

These kinds of experiments are so interesting. I wish I could simply implant some doctorate level particle physics knowledge into my brain. These are the kinds of things that start blending reproducible experiments with philosophy and causal finitism and how we know what we know, ya know? Sounds like hippie stuff but to me its fascinating.😁

[@samlevi4744]

You can. It just takes a while.

[@mr.loveandkindness3014]

@@samlevi4744 true that😂

[@thehulkamaniabrother2.089]

Derp

[@JustinL614]

@@mr.loveandkindness3014 We know what we know based on reason and evidence. Empiricism is the branch of philosophy for these scientific discoveries.

[@mrfashionguy1]

Why can't you? Apply yourself. With the plethora of great KZbin channels on the subject it's actually mot as hard to get into Quantum Physics anymore. Just gotta open your mind to some crazy shit haha

[@paulbrooks4395]

Maybe photons are discreet points and waves are continuous. Only when a wave ends does it look like a point?

[@lunyim]

Good experiment! Light(A comparison picture with examinations can not be included here) Left- reflect by splitter, mirrow and splitter. Right- pass splitter reflect by mirror and pass splitter a. no blocking b. right side block c. left side block I look at the results of video A Real Life Quantum Delayed Choice Experiment by The Action Lab. If examine carefully, b and c have already almost invincible patterns. b is brighter than c since c passed splitter twice The splitters and mirror influenced the qualities of light differently. Without blocking, the dark places are not darker than the blocked events. The brighter places are much brighter. So pattern is not because of waves interference.

[@beepboopgpt1439]

It's the most magical thing i know in physics. More magical than sci fi or other fantasy genres.

[@gnuffe7778]

Your way of explaining something is brilliant and you help me understand things that I never could have imagined, keep it up dude.

[@howiegruwitz3173]

It sounds like he's being molested as he talks

[@alexxbaudwhyn7572]

Describes my life perfectly. My wife always retroactively blames me for everything

[@markfernee3842]

What is shown here is just a classical Mach-Zehnder interferometer. So it is not surprising that the interference is a function of the presence of the second beam splitter. This is just explained using the wave nature of light. It is only at the single photon level that this experiment explores quantum properties. At that point the beam splitter seems to "decide" whether the photon is a "particle" or "wave" before the wave/particle choice is made later in the experiment. This highlights exactly why a photon cannot be considered to be either a particle or a wave. Rather, it is a quantum object.

[@timdecker6063]

It seems more likely to me that the photon is not switching between a wave or a particle, but instead there is something we still don't understand about photons.

[@direvosabostien3565]

I agree, there must be something else, though QM explains it well.

[@Ranstone]

Wouldn't a simpler explanation be when the splitter is removed, they're still traveling as waves, but since the two beams are perpendicular not parallel they don't interfere?

[@Ranstone]

@Rutger Ockhorst I see no evidence of that.

[@jarnevanbec2886]

Indeed seems plausable to me and as the simplest explanation is always the better one if it can't be disregarded, I will currently think further on this path.

[@anywallsocket]

@Rutger Ockhorst A 'single photon' does not make any sense - you can produce enough energy to emit a wave packet of particular energy, but since they are bosons, they are not classically countable.

[@yurikolovsky]

You real life demo is brilliant, thank you so much for sharing it! 3:30 "I guess we can accept that", let's not accept that, let's put an X on it and keep it as an unknown to prevent incorrect assumptions, we can also prevent the time travel element by using the "Pilot wave theory" way of thinking which is way more intuitive than the Coppenhagen interpretation which causes all of this to seem "weird" to the majority of the population.

[@borisrazmiki8296]

So everything in the universe is in the form waves, as if it were a programing code, and when we measure it, the code runs.

[@kootermccoglin6915]

God I really wish I was smart

[@SupremeSkeptic]

Do you mind telling us where we can buy the kit you used? And how much it costs?

[@paulrice7224]

By removing the second beam splitter at 3:00 and 3:24, the experiment "collapses" from a "double-slit"/dual radiation source experiment to a "no slit"/single radiation source "experiment", right?

[@shahariyardipto1103]

it may sound kinda funny but have you ever considered if the beam splitter was causing make the pattern? what i mean is there is no way you can measure with just a single photon. and there is a numerous number of photons that are colliding. so while the interference occurs or adding the splitter, the photons' path is changed by the elements of the splitter as it is also made of molecules. and they can absorb and reflect some of the particles. so i think the photons start acting like wave after it goes through the splitter but before. meaning the splitter breaks the photons from partical to wave

[@InShadowsLinger]

I am confused. When the beam splitter is removed only half of the beam is hitting the detector, so where would the interference come from?

[@quantranhong1092]

because when reflected the second beam now have a slight delay in frequency to the 1st path, when recombine it form interference

[@InShadowsLinger]

@@quantranhong1092 that is not the part I am talking about. When the second splitter is removed, they don’t get recombined, so I am confused as to why it is a surprise that there is no interference. There is nothing to interfere with.

[@joshdavis416]

Light can act like a particle or a wave simply because _everything_ is based off the principles of fluid dynamics. It's the same reason why a large flock of birds look like it's a massive wave form. Naturally, size matters, the larger the the particle (i.e. a single bird) the more space required to create the wave. An impossible amount of individual molecules creates our entire ocean, and each individual molecule would act very differently independently than it would in the whole.

[@jpe1]

I’ve never seen a flock of birds fly through two different openings and then interfere with itself. I don’t think your analogy scales bigger than small atoms.

[@joshdavis416]

@@jpe1 that's where visualization is key, and observation of the behaviors of birds in flocks would help. Just because you haven't seen birds flying through any type of opening before, or two flocks of birds colliding, doesn't mean it doesn't happen. And it's backed up by video evidence as well. I will add the caveat there are slightly skewed behaviors as a result of neural processing being a factor, so I probably should have used a more inorganic example.

[@mickyr171]

I wouldn't say that things are based off our understandings of fluid dynamics, we based fluid dynamics off what we observe in reality, also, its not an impossible amount of individual molecules that creates our ocean, clearly the ocean exists so has a finite number of molecules, the real question is, what are the molecules atoms protons quarks made from? they're ideas we created to grasp the infinite complexity that is reality, we base everything on our perceptions of what we can observe but we truly have no idea, we created the entire concept of science from the ground up, this is why movies like the matrix exist, why religion exists, and what science as a whole was created for, its our modern attempt at explaining our existence, there are many others that also could be true, my guess is none are true and the actual definition of our existence is beyond our comprehension

[@joshdavis416]

@@mickyr171 first off, I intended to imply it's impossibility to comprehend the amount of molecules that make up an ocean, apologies for the confusion. You're absolutely right, those questions are pretty important, but they aren't unknowable. Science was created, but unlike religion science seeks _answers_ . It shows that the mere presence of something is in itself proof that there is more knowledge to be obtained. One day, we may solve the big bang, and I guarantee it will raise more questions than answers. Science is an ongoing pursuit to understand the world around us, accept what we see, then keep persevering. Religion on the other hand, well, you know.

[@jpe1]

@@joshdavis416 you are quite correct when you point out that just because I haven't seen something doesn't mean it cannot have happened. When I wrote my comment I knew I was being intellectually lazy by saying that I've never seen birds interfere with each other, and I knew that that wording was suspect for the reason you point out: my observation, or lack thereof, of any phenomenon is nothing more than an anecdote. Let me phrase my point more strongly: birds, whether flying in a flock or singly, cannot exhibit wave properties, they are far too massive. De Broglie showed that the wavelength of a matter wave is equal to the Plank constant divided by the momentum of the particle, and for a bird that momentum is enormous relative to the Plank constant, the wavelength would be minuscule, something on the order of 10^-21m or so (again, I'm being lazy, I don't feel like doing the math, but feel free to do the math and prove me wrong). I have absolutely no idea what "video evidence" you refer to, but I am certain that it is *not* showing birds in a superposition interfering with themselves. The largest matter wave observed (and done in very carefully controlled conditions) was a molecule of fullerene that massed about 25,000 daltons.

[@Shadab738]

The same thing happens in Davison and Germer experiment and young double slit experiment the only difference is instead of photons electrons interfere with each other.Thank You action lab for refreshing my concept.

[@TotalKKK]

Photons aren’t exactly point particles, they just exhibit particle like behaviour. They are waves and the photon energy equation contains frequency.

[@fatalwir]

It's kind of mind blowing when you try to imagine it from our perspective. I personally like to look at photons from thier own perspective. Because of the relativity, they exist in all points of their trajectory simultaneously within a single point in time. In other words, from a photon's view it doesn't experience any time, so the second beam splitter either is in its path or isn't. There's simply no time for the beam splitter to move once the photon started its journey.

[@ninehundreddollarluxuryyac5958]

very few people see how relativity requires the photon to have simultaneous contact with the emitting atom and the absorbing atom even though we see time pass, the photon does not. If time doesn't exist for the photon, why do we see it as having a frequency and a wavelength? I never understood that.

[@fatalwir]

@@ninehundreddollarluxuryyac5958 Well, you can look at frequency or wavelength as properties which describe the amount of energy transported by the photon. The higher the frequency is (shorter wavelength) the more energy is being transported.

[@renedekker9806]

_"There's simply no time for the beam splitter to move once the photon started its journey."_ - it is more correct to state that the photon _does not notice_ the beam splitter moving, because it happens in the same instance of time.

[@jdtv50]

“They exist in all points of their trajectory simultaneously within a single point in time” what does that say about a video.. I mean , when a camera captures video footage, it’s splitting the incoming light into individual photons that are recorded and stored as a series of frames… You’re compactifying time. Like putting your finger in a laminar flow..

[@billjohnston882]

What is the equipment used in this experiment? Where can I get a beam splitter?

[@revilixjohnsen9496]

I am a fan of my idear: -lightspeed is not a real Barrier just the point where you bend space so much that you slow your Existence in space. -light punches infinit against that Boundary, so is infinitly slowed down. -so the light experiences no time and no Choice. The instants it hits the Detektor is the same as the start. But the light the Detector remits has that choice.

[@Shadow_B4nned]

If you can split the lasers and they have the same potential, why not just keep splitting the laser until you have more output energy than input. Effectively creating power.

[@codemeister3]

Is it not possible that the photons move so fast they create a wave? What about a vacuum? Shouldn't they warp timespace? Why is it choosing wave or part.?

[@ladronsiman1471]

photons don't have mass

[@codemeister3]

@@ladronsiman1471 then are they just waves of some particle we don't know? They can't be both, they can't choose. I think we r missing something.

[@Jkauppa]

you only add phase delay, make it seconds, so that the mixing time point is clear

[@Jkauppa]

you knowing affects the results

[@Jkauppa]

logic reasoning fails

[@Jkauppa]

make a better explanation

[@Jkauppa]

try uv-photoresist-photolithography on a silicon wafer disc in a stock blu-ray drive, just vacuum it

[@casparvandeursen7125]

I'm not sure I understand 3:25. An interference pattern isn't a wave, it's just the visible result on a different plane of when two waves collide like in water. If they didn't collide, you'd just get a spot without interference as we saw. Exactly as one would expect. I a missing why that implies that the photon goes back in time or knows its being observed.

[@samogufonianrockstar7510]

😊Found myself smiling the entire video!! ..Luvd it🙌🙏

[@silvenshadow]

If you only measure the peaks of a water wave you'll get something similar. It doesn't need to collapse. The wave functions that 'collapse' are probability functions.

[@rgerber]

didn't the slow-mo guys or somewhere exists a camera that can film so fast that you literally see the light moving and it looks truly like a wave

[@quantumbits]

I got it with the interference pattern up to about 1:50. "two beams of light.." ...but there is one spot. Then comes the particle detector suddenly I am lost. The particle detector has something to do with a grey square on the screen. Is that what the particle detector shows, inserted into the video or where the particle detector deflects the light? In any case there is nothing shown by the the PD that I can See. HOw can you tell they are traveling as waves or particles the hole time. This thing fascinates me but the apparatus for light duality and dual slit, sometimes eludes me. Thanks for trying. Im thick headed.

[@HelloKittyFanMan.]

You can just say "combining [something]," such as "combining both beams," because the combination already _means_ "...together." Much like the "re-" of "recombine" not only already means "again," but also implies the "back" already. So you can just say "recombine at this path."

[@rogerkearns8094]

03:38 I think the interference pattern should appear towards the right of the top beam splitter (not above it as shown) because it is the original beam, _travelling towards the right,_ which is reconstructed.

[@akashvishwanath1159]

The pattern will appear in both directions as half of the wave is reflected while the other half passes through

[@rogerkearns8094]

@@akashvishwanath1159 That seems reasonable, but I'm not sure that it's actually the case. (I could be wrong though; and thank you.)

[@deinauge7894]

if the distances are exactly equal on both paths, the middle of the interference pattern is dark on top and bright on the right.... the interference pattern appears because the photons are not exactly parallel and thus have slightly different path length on the two ways through the apparatus

[@rogerkearns8094]

@@deinauge7894 Thanks, I think I understand. So, over time, a photon detector centred to the right would register but one centred at the top would not? (This must be what I had been thinking of!)

[@renedekker9806]

​@@rogerkearns8094 _"So, over time, a photon detector centred to the right would register but one centred at the top would not?"_ - correct for the drawings, because the light source is to the left in the drawings. For the experimental setup, it's the other way around, because the light source is at the bottom in those.

[@danielhmorgan]

it may help to consider that we only know the detector detected; afterward it is speculation

[@fvsfn]

In the one photon experiment, if there was smoke in the room, i wonder if we would see the green trace on both sides or one side only. I guess smoke acts as a kind of detector so maybe there would be no trace at all as soon as the photon interacts with it.

[@brianegendorf2023]

My interpretation is that the wave doesn't collapse without the splitter..that's wagging the dog by its tail. It was always a non-interference pattern, until -un-splitting it created the interference. When the two beams in the upper right corner cross over each other, there is no interference because there is just that much space between the photons. Even though it LOOKS like you'd get collisions because they are at 90 degrees to each other, there is enough space for them to safely zipper without ever colliding. But when you use the splitter, you are now forcing the non-interfering photons to turn at the same spot, which creates collisions...which creates interference patterns.

[@ArturoTorras]

A different interpretation is that the photons are reacting directly to consciousness , and that they are not going back in time, but are instantly changing according to ones awareness.

[@rodrigoappendino]

Sabine Hossenfelder has a pretty good video about this experiment.

[@justindressler5992]

I think this is a demo of diffraction not wave/particle duality. The light travels In a straight line through the entire experiment. It only randomly changes direction when a none reflective material is inserted into the path causing it to randomly change direction as it interacts with the material. Also the light isn't vary linear in this experiment. As it scatters into a large dot instead of a small point. Again this happens because of interactions between the mirrors and even from the source, since the light is emitted from the laser diode junction in a random but probabilistic direction of observation away from the diode surface. There are well established mathametical solutions for light which only ever transport the light as a ray. The rays contain a wave function but this only effects the characteristic interactions of the ray when it interacts with matter. For example a red frequency ray will interfere with a blue frequency ray but only if they arrive at the same point in space. I suggest you use a transparent interference panel and observe how the light continues in a straight line since something like glass has a low index of refraction. Eg it does not change the probabilistic direction of the light. This experiment is based on a vary early experiment which was done before modern mathematical solutions were developed to describe light transport. We can easily simulate light in a physics based way using only ray based projection. I think the hardest bit here to understand is that the light is not transmitted a one single particle but trillions of them. These particles arrive at the same destination at the speed of light so they appear as a dot scattered of centre axis from the laser. If you could slow light down to a particle or a prefer the term packet. Because a particle would imply the light consists of matter which it doesn't. It would not be visible for many reasons including its energy not having enough interaction with the camera sensor to be distinguished from noise to the probability that it changed direction entirely away from the camera. The unique thing about the lens of our eye and the camera is that it focuses the light from many incident angles to a central point effectively amplify or increasing the chance the light will be recieved by or retina or camera sensor. A clear example of light refraction can be seen by putting the laser in a vacuum it will no longer be observed from a perpendicular angle as it has no atmospheric matter to interact with. These tricks of light occur because you are witnessing trillions of sudo (probablistic) random interaction of energy arriving at the witness lens of the camera or eye. We can never ever witness a single particle of light it would never be distinguished from the trillions of background rays we receive from every visible star in our universe. Probably the best example of a ray of light is that witnessed from space as the field of view for a star is so small that it appears as a single dot but in reality its energy is projected in every direction simultaneously. But if we could bring the star closer we would see more detail as the light would start to arrive from more angles to our eye, like our sun. If we were to put matter between our sun the light may interact with the matter in different ways it might bend around the curvature of a planet to appear a little like a hallow or reflect light a spot lite in the case of the moon.

[@blakewright575]

Thanks for your content! Since the photon is traveling at the speed of light, wouldn’t the time you altered/observed it be the same time as it was released from the perspective of the photon? Asking for a friend.

[@ward6238]

Photons don’t have a perspective. Considering a photon’s perspective is like considering marshmallowing an umbrella at lamp o’ clock in the morning. There is no discernible meaning to it. Special relativity dictates that the speed of light is the same in all reference frames. If light had a rest frame, it would be moving at the speed of light in its own rest frame, which is absurd.

[@kaushik2758]

I think the second beam splitter is producing a bi-directional double slit effect. The reflected waves from each ot the mirrors are emerging onto the 2nd splitter where again 50% of each wave is producing the interference. Similar to the unidirectional double slit experiment. I would like to request this channel to check the interference pattern on the other 50% direction.

[@andruss2001]

Thanks! Good video. If the photon travels through the first beam splitter being a wave and then we remove suddenly second beam splitter, the wave collapses (collapses all the way back till the light source?). What if we would say that time doesn't exist at all, but the whole our reality is like recorded on a video tape, and then what happens, is that a few frames of the movie were instantly rewritten, so that there was never such a timeline where the photon acted as a wave at all. All what's left is in our vague memory.

[@kiwik3313]

The fact that the contraptions werent aligned with the rug drives me crazy 😂😂😂

[@TeabaggEditing]

There are so many awesome experiments with light. Somehow still unbelievable how it is a particle and a wave at the same time.

[@howiegruwitz3173]

It's not. That's like saying an mp3 and a singers voice and the microphone and the speaker are one.

[@anywallsocket]

@@howiegruwitz3173 exactly. the wavefunction models quantum behavior BEFORE it is measured. measured quantum behavior is necessarily eigenstates of the wavefunction, which are particle-like in a sense.

[@knifedreamer]

Would be really interesting to see still water funneled in a vacuum chamber, which way would it go?

[@leonardyancejr.2903]

if you can see the beam its diffracting in your eye....try this with a single photon detect adjacent to it path...90deg etc...

[@iainmackenzieUK]

Please confirm that the laser only produces one photon at a time. And lets be clear just what that means in the wave model too.

[@Botanifiles]

Removing the second beam splitter would require breaking the speed of light

[@jetison333]

Why? You just need long enough beam paths and synchronized clocks. This is an experiment that's actually been done.

[@Botanifiles]

@@jetison333 oh, good point

[@nabhasan]

Try to view the source from pattern side.

[@dudethethe2548]

I always struggle with the concept that we can control the experimental conditions well enough to separate and send single photons?

[@TheRenaff]

Given that the photon is moving at the speed of light, isn't it possible that the special relativity effect of length contraction is at play here such that, in the photon's frame, you removed the second splitter AT THE SAME TIME the photon was emitted, while for you it seemed like it was midflight? As the "ladder paradox" states, simultaneity of events depends on the observer's frame. An event that is simultaneous in the photons frame may not be simultaneous for you.

[@leonardyancejr.2903]

What if photons travel as streams of particles at angles and diffract by an atomic medium density until they create a wavelike pattern on your backdrop?

[@alexd.3905]

do I understand it right that when "water" waves interfiring it means that "water" is in super position?

[@haithamannaji4790]

I think light is just a particle orbiting around around a mass infinitly small and dense in space time like planets that's why we see it as a wave and particle. If you think about it all the Pi in the equations refer to a circular motion and even frequencies translate to the position of a point in a circle. When you stop to detect it's position than you tooked a screen shot for a position in space time and reality colapse from it's continuity to a certainly in time. Just my thoughts light is like the block of reality itself since nothing is faster than light and it literally defines time. Let me know what you think

[@spynorbays]

But a photon travels at the speed of light, meaning it cannot have a property of time, past and future is the same singular timeframe for the photon. So technically a photon's state can never be different between two sets of time frames for an observer, it's either always a particle or always a wave. If it needs to be a wave, it was always a wave, since "always" is only valid if you're an observer.

[@spanky541]

Thats kinda cute. There are many unknowns to QM to assume the things being 'seen'. Do u think its possible thata reflection energy is traveling the other path, although at a energy signature so slight its 'un-observable' until somthing additional is put into its path to re-refract the energy making it seem as if its wave 'observable'. That couldnt be it tho huh. 😁 happy holidays all.

[@luckypegasusvol7700]

What if the schrodinger's box was empty?

[@ChandrasegaranNarasimhan]

May be delaying the pulsed laser where a single photon is fired more will make the interference pattern go away. If i am right, please let me know.

[@Packedburrito]

How do we know that the light particle and the light wave are both light? It seems like it's more of the photons being boats in the waves of space, like how do we know that the photons and the waves are the same thong and the photons aren't just making the waves when they move in space and get moved by the waves of the other photons in the space?

[@shayanalinejad8059]

Hello, I wanted to ask you to put two different containers, one wide and the other narrow, containing water with the same mass and initial temperature inside the vacuum chamber, so that we can see which one boils faster? . I think that water in a narrow glass will boil faster because it will have a lower temperature drop than the other one due to surface evaporation before boiling. Thank you for doing this test, friend . 💙💙💙

[@Josh729J]

I think the wider one will boil more quickly because you have a larger surface area in direct contact with the flame.

[@luckypegasusvol7700]

Put some money in a box and close it, would the money be in a superposition while the box is closed? (You cant make a measurement when box is closed)

[@westonding8953]

How do you think magic tricks work? Lol

[@luckypegasusvol7700]

@@westonding8953 bro ):

[@westonding8953]

@@luckypegasusvol7700 Check out Tom Stone’s Quantum Logic (Whose box is this?!) magic trick! I don’t know how everything works given how much of that trick is observable! I know some of it though.

[@alexcornflow]

A time traveler won't be going to parties coz they know they're experiments. It'll expose them lol

[@gator1984atcomcast]

Each wave is discrete, separate, individual, as in digital. The energy of each electromagnetic wave is associated with one Plank quanta of energy.

[@LemarFrench]

Why does the second beam splitter mean they traveled as waves in the beginning...if the second beam splitter bisects the second photon beam split from the first beam splitter with a perpendicular photon beam

[@celebratedrazorworks]

Uuummm... Am I trippin or is everyone missing the fact that the beam splitter is a closed loop at first, when it hits the 2 mirrors we assume "yes now it recombines" but then the beam gets split up after the second interaction with the beam splitter and 50/50 again sends half of the protons off to nowhere! The sensor can only be in one place so then what's the effect of the missing information? Pretty sure there's sumthin goin on there! What happens when you combine the corresponding interference patterns?

[@miklov]

What even is an individual photon? Isn't the energy contents of a photon the energy absorbed by the interaction between the light and a sensor in order to do chemical or electrical work? How can we prove there is a smallest unit of light without involving electron shells?

[@bjlbernal]

How do we know photons are not carried on waves or are powering the wave that carries them? Could that be why we think they act as both particles and waves?

[@アニメ2-s6b]

ACTION LAB I NEED YOUR HELP. if you get a wooden spoon and place the very end of the handle against the speaker on your phone then close one ear and put the actual spoon part on your other ear you can hear the sound coming through the spoon HOW.

[@nathan-shearer]

Time slows to 0 as you approach the speed of light. From the perspective of the photon, it is emitted (as either wave or particle), interferes (or not) and is absorbed all simultaneously. There is no need for the photon to retroactively travel back in time since it experiences no time.

[@DrDeuteron]

Light in air is slower than c so your argument fails

[@unironicdoomer614]

Can we see the observer affect too ?

[@ulibarcj]

So if the photon is moving at the speed of light, and we don't have a way of achieving light speeds, how do you remove the second beam splitter after the photon is moving but before it reaches it's target? Wouldn't that require a faster than light reaction to achieve?

[@renedekker9806]

_"Wouldn't that require a faster than light reaction to achieve?"_ - not really. Just a long distance between the first and second beam splitters, so it takes time to travel. You don't detect the generation time of the photon. You only deduce from the travelling time that it must have passed the first splitter already at the moment the second splitter was removed/placed.

[@ulibarcj]

@@renedekker9806 Fascinating. I've always been interested in the subject but there are some brain bending concepts involved lol. Thanks for the answer!

[@kumarranganathan3199]

You could do the same with two wollatson prisims

[@yingfortheking]

What if the alternate path is facing the opposite direction? Would the photon appear at the 2nd sensor instantaneously or delayed at the speed of light?

[@rpals5412]

what you say at 4:16 was my exact thought the whole time. It must be a wave at all time until it "interacts" with anything i.e. gets absorbed in some material (collapses the wave), and now we can draw a line back to its source, and say "a photon travelled on this path" - all though it was always a wave, and could have collapsed at any other possible outcome. It doesn't really make sense talking about photons before they are detected, as soon as photon is detected, it is not light anymore, but have been converted into heat - that's literally how we detect them. There's a huge a common misconception, that photons can be detected and still remain a photon that continues traveling, but that's not true, after the photon is detected, it is no longer light, and it could have been a wave at all its life time, but it happened to collapse at a certain point on our detector, and for some reason, we find it meaningful to then call it a photon which resembles a particle.

[@muffininacup4060]

If its a wave hitting something and heating it up, why even say that it was converted into a photon? We dont say that microwaves in our ovens convert into photons or smt else to hit the food and heat it that way; do we have to have a kinetic interaction for heat to occur? I feel like there is no point in calling it a particle; if we are observing a specific path, I'd say its not that a particle flew in a specific way, but rather that we are observing the specific instance of a wave, its state stopped in time, rather than a path of a particle.

[@renedekker9806]

@@muffininacup4060 _"why even say that it was converted into a photon"_ - because there are physical effects, like the photo-electric effect, that cannot be explained without assuming that light consists of indivisible quanta of energy. By the way, photon detectors don't detect the generated heat, but the electrons that are released when photons are absorbed.

[@rtbeerzi]

So... I'm only confused on the axiom: Exactly what causes the difference? What circumstances cause a light to act as a particle vs a wave and clearly if it can choose to be one or the other, it is neither If I can choose to be a dog, or a cat, then I'm clearly playing a video game: I'm not the dog or the cat until i choose So what is light before it chooses A or B? What decides whether it is A or B? It can choose to be a wave. It can be a particle (I'm using "choose" loosely) and somehow I get the sense that it can't be either of those if it can pick which one. Is there something half way between a particle and a wave? And if being a particle or a wave is on a spectrum, or even a binary, that would imply implicit laws of nature: Fundamental Causes. For something so based and inate within reality, that its choice is the Fundamental action of energy: That thing.... It's deep. Which I believe is, impossible in QM. You can't have the basic "cause and effect" System work. I just don't think we'll understand it until we understand Quarks better or involve that into the equation, and finding out exactly what they do other than exist

[@hoofheartedicemelted296]

Pity you couldn't produce a phase conjugate mirror with your setup sir. I believe strange and exciting things occur when it is encapsulated by an em field with a specific frequency.

[@ragarriott]

Where can I buy that demonstration device? Link please!

[@Spedley_2142]

What if a photon is much bigger than a 'particle' and covers the whole experiment at once. Rather than imagining a single particle travelling through space imagine a large moving region of probability. If that probability encompasses the whole experiment then it is possible for the actual paths the photon takes to be defined before it appears to travel along them. It could also cause interference between successive particles if they were not spaced sufficiently apart in time.

[@ronbally2312]

Why would “the” photon leaving the laser even arrive at the screen/ detector when it has passed through media that has electrons to interact with, as it surely must with the beamsplitter in place?