+AlphaMineron Close, but rather it's the collapse of the photon's wave function. One of the fundamental quantum mechanical laws is that upon measuring a quantum system such as photon passing through a slit, the photon's probabilistic wave function "collapses" to keep producing the same result measured previously...nobody knows why and we just accept it as fact.
Look up the quantum eraser experiment. They use a crystal to split the photons into two identical (and entangled) photons. One is sent to the detector, one is sent to a series of mirrors. The mirrors 50% of the time lead to detectors that will tell which slit the photon went through, and the other 50% of the time it destroys the information. The second set of detectors is placed far enough away that the photons hit the main detector before the second photon ever hits the mirrors. Even after all this, the photons that you can determine the slit it went through do not show an interference pattern, while the other photons, where you've destroyed the information, again show the interference pattern. It's as if one of the entangled particles goes back in time to say "hey, they figured us out! quick, be a particle!"
DaffyDaffyDaffy33322 I don't understand that experiment. I think I need some time. I tried watching the PBS Space Time video on it but it's quite confusing.
When i was in 9th or 10th grade our teacher showed us the double slit experiment with a laser and we could see the interference pattern in the dark classroom. Now i feel really thankful that i had the opportunity to witness this live and become fascinated by science. Sadly i wasn't so aware of that when i was at school, but i think deep inside it helped to build up a fascination for physics and science in general.
I had many thoughts and questions after seeing this video: 1. what is the size of each slit? how far apart the slits are individually? what is the size of photon or wave? at what distance the light generator is from slits? and how far is the sensor/receiver? 2. What if the each slit is closed alternatively? 3.what if there are more than two slits? 4. what if we place two photon guns at an angle to each other to fire photons through single slit and try different options? 5.what if we place two photon guns at an angle to each other to fire photons through double or more slit and try different options?
This is amazing knowing that one of the chapters we are taught in last year of high School (or a lesson) is so close to the Quantum Mechanics. I am 18 and I am happy that I could find out that my high Physics whether it was newtonian physics or any other branch... Believe me when I say "it was was astonishing!"
We spent close to two hours covering this topic in Physics today, this video contains everything that the teacher taught to us in two hours but in 6 minutes.
I totally love what you're doing here. You're like the perfect mix of my physics and chemistry professor from High School. I've been wanting to re-visit this, and some of the other items you've touched on, just to refresh my memory, it has been 30 years since my last formal class. Thanks!
Quantum Light (h) is a dualistic quantum particle that in the cosmic vacuum can fly at a constant speed (c=1). In this movement, light uses its linear spin and it does not produce electromagnetic waves. Light behaves like a corpuscular. But light can behave like a wave if it uses its angular rotation (the torque required to accelerate angularly around the axis of rotation). In this situation, the speed of the light is faster than the constant. The speed is c>1. This situation is explained by Lorentz transformations. The problem is that we do not know the geometric shape of the light quantum.
I have a great word. Golfbal. In Dutch 'golf' besides the sport is also the proper translation of the term wave. We also don't use spaces when we use word combinations so golfbal would be a 'golf ball' or literally translated 'wave ball'. I always joke around with this at my university since its quite funny if you are Dutch.
Derek, This is a very interesting topic. I hope you do more videos on it. I summarize what's going on this way: "things travel as waves, they appear as particles". It's true for all things - just not very noticeable for big things which are collections of a bunch of small things travelling as waves and appearing as particles. You'll notice that with mirrors and beam splitters and slits and screens you can get the wave to bend, split, or pop. When it pops - that's the wave manifesting as a particle. I think you can get deeper insight into this by asking yourself - "why is it that fiddling with the wave sometimes makes it pop, and sometimes not?" What is the boundary of fiddling that just under it the wave continues - although perhaps bent - and just above that amount of fiddling and it pops. What are the factors that determine how much fiddling can happen before popping occurs. Also when I see a wave pop - and you watch the same thing - do you see it pop to the same place? I've never seen or read about experiments along this line. If you can - can you do some experiments along those lines. I don't have access to equipment to do it myself.
*EVERY QUANTUM THEORY IS WRONG* I said this, and I will say it again... A photon is not a particle with wavelike properties. It's a wave, that localizes it's energy upon interaction due to energy transfer. Like a cloud shooting lightning. Which turns it into what we OBSERVE as a particle. It's not both at the same time, and it's not at multiple places at the same time, neither is energy transfer that's faster than light possible through entanglement. NEITHER is the schrodingers cat experiment's superposition broken by us looking into the box... All we know is that (once measured/observed) the "wavefunction" collapses and we get a point. But we have been concluding wrongly about the origin properties of quantum particles. For a quantum particle to be measure there has to INEVITABLY be an energy transfer between the quantum particle and the measurement apparatus. THIS is where the quantum particle suddenly appears to us as a particle... But it was never a particle. It just localized its energy when measured. The nature of quantum particles has fooled us to believe they are particles.. They were never particles.. NOT quantum particles... They are quantum *WAVES* or rather: quantum *excitations.* Mark my words, for in the future you might learn this in some video. After we finally figure out I wad right. The measurement system breaks the "quantum wave" into a particle due to the interaction between them..
@randomshittutorials There's a good bit of questions I have but first do you know if they have done experiments or anything to show if our eyes observing from a certain potion or something collapses the waveform too? I ponder that because wouldn't our eyes cause some sort of energy transfer too collapsing the waveform. If that's true then I completely agree with all you've said and I'd honestly like to message some more. I've been deep in thought about similar topics
@@randomshittutorialsI do keep having this sense of wonder “is anybody thinking, hey, I don’t think we have this correct.” I feel like we are at the tail end of a super difficult sudoku puzzle and realizing we got it wrong but no one wants to start over
@@Yellow-Viridian834 Sorry to keep you hanging so long. I am still convinced my deduction based on countless information is true. The thing is, our eyes are the same as the measurement apparatus. The photons hit specialised cells, that turn the interaction between the photo and our cell into electrical signals we can process. For this to happen, the photons HAVE to interact with our cells, which means, by definition, there is an energy transfer, just like with the measurement apparatus. The problem is, that our eyes and brain aren't precise enough to measure a single photon.. This is why we use the experimental setup which documents the results on a piece of flat reactive paper. But, yeah, our eyes would also collapse the wave function by that logic. It does so all the time. It's why you can read this message.
@@josiaphus Well we know it's not complete. We say "not complete" because we've proven that what we know works 99,9% of the time. It's too much proof to say it's wrong, but it surely is incomplete, and I believe most people look at this subject with scepticism, but most also understand that due to the unintuitive nature of these physics, yapping like drunk idiots won't resolve anything. And most who think they know, are wrong. I am almost surely also wrong, but I still believe that my deduction is SO MUCH better than this, being at multiple places at once BS. Or it being a particle AND a wave. It might be due to my caveman brain, but I have to this day only found ONE experiment that seems to defy my idea in a way that makes sense. It was a variation of the double slit experiment, with mirrors that had a chance to let the photon through or not. Photons seem to be able to be at multiple places at the same time, as it reverted back to the old path when the other one became unavailable, even if it was already past a certain point of seemingly no return. This throws dirt in my visualization of what I thought a probability wave is... It seems to be more than only a wave. But at that point I'm just yapping. I have no clue why it does what it does.. I hope the great scientists of the world will give us new answers. Till then I still don't believe they are a particle and a wave at the same time. But maybe due to the nature of a wave, it can be at multiple places at the same time. It depends on how you define a wave's location.. What I will still push is that, iquantum particle, are not particles, they are waves, who act like particles upon interaction.
Long before I ever heard of physics, my mother had started me on a quest to figure out magnetism. By 5th grade (1963-1964) I was working on self-sustaining experiments. The reason a photon acts as a wave and a particle? the particle forms from the wave. When a wave 'breaks, a string remains with + and - ends. They are attracted to each other, and we come up with the snake eating its tail, but in this case, we have energy passing through energy. The only way for this to work is for a vortex in the center to form, much like a figure '8' or a strand of DNA.
I literally did the slit experiment in my room using paper, cardboard, and a laser yesterday. It was absolutely beautiful and mind-blowing!! Highly recommend.
I think the answer is quite simple but I could be wrong. Everything is made of the same energy when you get down to the quantom levels. We just experience them as different wavelengths and frequencies. When you do the double slit experiment with multiple electrons you see the wave interference patterns from doing a unrestricted observation. By shooting "one electron" at a time the only thing you are doing is changing the rate of speed at which the wave is passing through both slits, thus you are getting the same interference pattern over a longer time, but when you put the detector up and restrict your observation parameters to "50%" or (one slit or the other) that's the only result you will see is one or the other because you have narrowed the observation results from an open ended observation to a (one slit or the other restricted one). It's like narrowing your experiment parameters down to only 2 frequencies of light, only seeing the red and yellow frequencies of light but then asking but why am I not seeing the entire rainbow? It's because their act of specifically only measuring one slit or the other has resulted in them only seeing one slit or the other. By narrowing their observation window they have narrowed their results. Explain how I'm wrong @Vertasium
I think you must first prove that there is such thing as "single photon" and you are actually tracking it. As far as I'm concerned, you made the same experiment, with lower intensity light, and the pattern is just less visible... Actually I would be shocked if you got anything different, that would break the most fundamental idea of the field as something continuous in space. What you did is just lowering of the field to the point where your measurement system struggle, nothing fundamentally different... My vision is that what we call "photon" is just property of the field, and the only way to be shocked is to assume something wrong in the first place - that it's a "particle" and you can "track" it.
I know it's been two years since you posted but i am just now seeing this video. After reading tons of comments i was feeling frustrated until i came across yours. I feel like you perfectly expressed what i was thinking as i watched this video.
@@dreamdiction There are also no waves either. There is only a quantum mechanical state vector for the light and a measurment. The thing is coherent sources have a very particular state vector withi is not a real "one photon state". I would like to know what happens with SINGLE PHOTON SOURCES. This is. sources that generate photons with a single photon quantum state (not a coherent state), or in other words, an eigenstate of the fock space with n=1. These states are not superpositions (as coherent states are, and do not even have oscillating magnetic or electric fields). Single photon sources exists and there is much interest in them with applications in quantum computing hardware. But they are really state-of-the--art hardware. I'd like to see what happens with the interference pattern when one of those are used.
@@Brucebod If you read some (or rather a lot) of quantum mechanics you may understand what is really going on here. The important part is the quantum description of the light as a state vector. It really is neither a wave nor a particle. Is a quantum object. Also you can't deny the "particle" aspect of the experiment. You detect INDIVIDUAL photons after all. If you have any doubts, just go learn some quantum mechanics.
@@PsiSubDiego "If you have any doubts, just go learn some quantum mechanics." Aggh, I'm trying, I'm trying. I guess i am frustrated because I still cannot understand something that i _really_ want to understand. I will keep trying, tho.
I would love to see a video that discounts all the other possible explanations for the same result being obtained whether particles are fire one at a time or sumultaneously. It seems a pretty big leap (a quantum one in fact) to arrive at a quantum explanation, without first discussing the many possibilities that mechanical physics offers.
I agree. What if the entry-point detector that, when activated, apparently makes the photons appear (as classical physics would have us expect) as dots, rather than as waves, on the screen, were somehow 'processing' the photon, changing its physical properties?
When you have 2 or more paths you add "probability amplitudes". which are just arrows that turn like hands on a clock very fast, and stop depending on the time light takes to go those paths. When there's one slit open there is only 1 arrow. When 2 slits open there are 2 arrows. Any path to any point on the screen where the arrows point in mostly the same direction has a band of light, any path to any point where they point in opposite directions there is no light. Simple as that. Goofy as that.
3:49 Could you say that it travels as a wave, but interacts at a point? I feel like this is a pretty intuitive explanation, but I've never heard it said this way. The explanation that makes it seem mysterious seems to always be preferred. It travels as a wave, and collapses to a point when it interacts.
I think that when a single "photon" is emitted by one accelerated electron is, as Maxwell says, an emspherical em perturbation wave in the 3d space; when this wave is passes through a single or double slit is diffracted but is still an em wave that become a photon oly when interacting with the screen. This is also a "measurement". Nice video.
Yeah well. Sean Carroll sometimes tends to oversimplifies things for his divulgations talks. There are just waves, or to be precise quantum mechanical waves, which is quite different from electromagnetic waves from Maxwell's equations.
@@codyramseur It seems to me calling quantum mechanical objects "just waves" is more of a spherical cow than acknowledging that they are neither (as quantum mechanical equations and experiments clearly show). Or are you suggesting there is something wrong about tha QM description?
Now there is a theory that photon IS a particle but space is the wave behavior, so even if you shoot one single photon throught the slits, the photon will follow the space wave. Like a boat on water it will go straight but follows the wave of the ocean. Maybe you need to go at the speed of light to behave like a wave. If you could shoot me at the speed of light like a particle throught a giant slit, I, the particle, would follow the wave of space making me look both like a particle and a wave.
+bob roger A photon ISN'T a particle it's closer to a form magnetism in fact, like gravity. Tesla was closer than Einstein and the Quantum clowns. One could say everything is magnetism and yes atoms themselves. Then there is the aether or counter space...
+bob roger I like your thinky thoughts. Prime in my mind when considering light's properties is "what the heck is waving?". We understand how waves move through water, waves through air is what we call sound, what is the MEDIUM which is conducting electrical waves? The wavy space idea is interesting...
+bob roger What about electrons that exhibit wave like behavior? They aren't massless so they cannot travel at the speed of light of course they certainly are fast. At what point does matter cease acting like a wave? I don't think the theory you're talking about is all there. :/
After thinking about the results of the recent "gravitational waves" experiment, and watching this video, I arrived at the same conclusion as the op above. I came up with the following analogy: Think of a particle of dust, or sand, inside the vast ocean. On the very top layer of the ocean, one could observe the sheer force and violence of the waves. However, once you dive in, deep, those forces no longer apply in the same manner, though, they are there. A a particle of dust, sand, or what have you, will move in a wavy pattern as the forces of the ocean propagate and reach the particle's destination, each time giving you a slight push up or down, and foward. If we think of light in this manner, where particle of photons are carried by the gravitational waves of the universe, then we could explain their wavy pattern. This morning I woke up with a question: could we expect photons to appear at a set percentage in a given spot? In other words, could we expect photons to be at a given place with an expected percentage of probability? Please, any one who might have the answer, I'll much appreciate it. Thank you.
I've always thought that light was particles that move as a wave. Much like with sound, there are points of high and low density in the concentration of particles. The particles themselves are also moving forward in the same direction as the wave, and it is the incredible speed of the particles that make it difficult to differentiate between the types of movement. Since photons move at slightly less than C, there is still enough of a difference between the two types of movement (linear and wave) that this doesn't seem impossible. The information represented by the wave can translate at exactly C, while the photons themselves are slightly limited by the energy representing an infinitesimally small mass. I'm not sure I've explained this very well, but am I entirely wrong in the way I understand this? It sounds like you're saying they couldn't possibly exist in both states at the same time, but it still doesn't seem unlikely. A wave is just a method of travel, a contracting and separating of particles. It's hard to visualize something that both moves forward and has an elasticity of speed that would allow for wave propogation, but I'm nowhere near adept enough with mathematics to validate or disprove the possibility. I hope I haven't taken too much of your time with an inane question. If you have read this, I appreciate as much as that. Keep making awesome videos, Derek; As much as I enjoy other science related channels I never learn as much with Destin or Michael as I do from you.
by light he meant "electromagnetic waves", long wavelength(low energy) waves like radio waves are hard to block, but higher energy waves like visible light, can be blocked and measured to the level of photons.
The photomultiplier has sensitivity to single photons strikes, which is how it can read out that the background rate is 4 or 5 of them per second. They don't all hit at exactly the same time or same place, and most of them probably did not pass through the slits, but hit the photomultiplier from other angles: at this low rate, they will not have significantly interfered with each other in the experiment. You don't need to reduce the background rate to zero to see (eventually) that some regions have significantly higher rates above background than others.
there are no photons, then there would be a red green and blue photon they part of the eletromagnetic spectrum light is just a free form of energy with a certain wavelenth or charge
I thought about this a lot when going to university and also afterwards. Clearly from the double slit experiment (involving multiple photons through both slits) the resulting interference pattern appears to be a function of photons constructively and/or destructively interfering with each other. However, clearly from the double slit experiment (involving single photons through one slit) the resulting interference strongly suggests that individual photons constructively and/or destructively interfere with themselves. So, that suggests another particle is present. Above, I mentioned that I thought about this a lot when going to university and also afterwards; and what I concluded was this . . . . Since quantum field theory (QFT) stipulates that every particle has its own antiparticle, provided that particle is charged, it introduces the possibility of an anti-photon. QFT also describes what properties each antiparticle will have from a space-time perspective within the context of (when compared to the matter particle) equal mass/spin and opposite charge. Since most photons are not charged (at least as far as we can detect) one interpretation of the QFT that follows is that no anti-photon exists. However that is only one interpretation of QFT as it applies to photon particles; itself reliant upon the assumption that we know everything there is to know about light; in all the dimensions it may exist. Another interpretation of QFT as it applies to photon particles is that (despite the photon apparently possessing no charge) one can still - by retaining mass/spin and substituting charge polarities - employ the construct of the anti-proton; particularly since this seems to do very little to the photon. For the most part, respected sections of the scientific community accept that anti-photons exist. So, given the above, uncharged photons can be their own anti-particle; or anti-photon. Furthermore, charged photons also have their own anti-particle; or anti-photon. Many particles are their own antiparticles, such as force carriers like Gluons, Z boson, and Photons; some of which modulate and/or interact with nuclear and electromagnetic forces. So, the above discussion provides for a simplistic insight into how/why the double slit experiment that seemingly involves single photons fired through one slit, still results in a constructive/destructive interference pattern that resembles what happens when multiple photons are fired through double slits and interfere with themselves. Now, how (i) the Pauli exclusion principle, (ii) the fact that, since photons can be their own anti-particle in ways that mean that photon numbers are (unlike Leptons/Quarks) not conserved, (iii) it is considered that photons can annihilate themselves, (iv) any relativistic and/or multi-dimensional considerations apply to observed results . . . . . Remains to be seen and is outside of the scope of this discussion In any regards, I have always thought that the consideration of the above (particularly the existence of photon and anti-photon pairs {whether they are the same particle or not} within the dimensions we do and do not perceive) is the best starting point for trying to understand the dilemma of the double slit experiment. Not in the least, as the existence of photon and anti-photon pairs provides for (at least) a starting point that seems to have some possibility of explaining how interference patterns requiring more than one particle are still observed when (it seems that) only one particle is fired through a slit. Never say never, as (in a similar way that Planc Stars are neither proven or disproven) I still think it is not perfectly clear whether or not a star can exist that is so large and massive (think 1 billion times the distance of our solar system) that when/if a component of its inner core collapses - despite it later creating a black hole - the subsequent recoil force is not enough blow the entire outer shell away and into a supernova; leaving an inner spherical radius that is slowly eaten away whilst also bombarded by the energy of the black hole’s accretion disk and other ejections.
Any updates on your conclusion. Any neew information. I was operating under the conclusion that photons are packets of energy that warp space around it. one side is pushing space away from energy and the other pushing into itself. I think of photons as particles that are balanced by space
Thankyou Derek! This is the first time that anyone has actually explained what we are seeing in the double slit experiment. Yes many people explain that what we are seeing is an 'interference' pattern but they don't explain how the troughs of the 'waves' (or should I say 'wavicles') are caused by the extra distance that light from one slit travelling at an angle to light from the other slit has to travel and how the peaks are caused by light from both slits coming together from the same angle so that the light from each slit travels the same distance. We can understand this if we consider light to consist of waves. But when the same experiment is done with single photons - then it gets weird.... The same interference occurs, so a photon is actually a wave as well as a particle? Hmmm!
The confusion stems from the assumption that electromagnetic waves are quantized. They are not. Photons are interactions between atoms and the electromagnetic field. That interaction is quantized. Once an electromagnetic wave propagates, it can have any intensity you want: a billion photons, or one tenth of a photon, it does not matter. The wave properties remain, so that interference is still happening at a slit. There is no photon traveling as a tiny wavelet along the laser line. It is the electromagnetic field that is supporting a coherent wave from source to target, where we let it interact with sensors.
There are no real "particles". Particles are really theoretical center points of complex electromagnetic wave fields. They represent the center of peek magnitude and the field's energy signature at the point of observation. These "particles" have huge extended fields and it is the extended field that passes through the second slit, that splits the single photon filed and causes interference 'with itself'.
relaxxxrrr Does it represent the peak? If we measure, we get a single position, like a particle. But that position doesn't need to be at the peak, that's only the most likely part. So I don't think it's fair to say which specific part of the wave is a particle until after you've measured it, but then the wave is gone...
mdilligaf Are we really measuring a single position, like a particle? "Particles" are at least 10 thousand times smaller than an atom. Is the equipment in the video really counting single photons or is there some misinformation going on. Look at the resolution of the sensor, tenths of millimeters is nowhere near "particle" resolution. Wavelengths of light are a million times smaller than that. Observation of the quantum world is a real problem, I think the best resolution we can ever hope for is no smaller than an atom. A photon or any particle striking an atom is observed as an increase in energy of that atom. The exact position that a "particle" collided with an atom can probably never be known. The dot resolution of the experiment in this video is trillions of times larger than any "particle" accuracy. "At the smallest scales there are no objects, only relationships" - Greydon Square
You don't need high spatial resolution to measure single particle interference. If you want to make sure it's single particles, the important thing is the time between events. If there's one count every few seconds, then you're probably counting single particles. The detector needs to be only small enough to distinguish the maxima. It doesn't matter if millions of particles fit in one 'pixel', as long as there is only one.
relaxxxrrr In case you're interested in measuring positions with high resolutions (smaller than the size of atoms, though that's a vague concept). The scanneling-tunneling microscope can already do that. It works with piezo crystals (for moving tiny amounts) and tunneling (to measure distance precisely). Has little to do with this experiment, but since you talked about spatial resolution...
relaxxxrrr When the wave function of a "particle" interacts with the detector screen, a phenomenon called "wave function collapse" happens, in which the function "collapses" into one of the position eigenstates, and dislodges an electron on the surface of the detector in order to create a "spot". But it still remains a wave even after the wave function has collapsed (may be a highly localized one like a dirac-delta function, but it's still a wave). So yes, you are right. Typically in non-relativistic QM you have one wave for each "particle". So the right statement is "a particle IS a wave". But of course in light of QFT, there is actually a single wave function that encompasses all particles! The "wave-particle duality" is really a vestige from the past (early 1900's) when QFT was not developed and quantum phenomena were less understood.
One explanation is that light goes through both slits as a wave with probabilistic uncertain ∆×∆pᵪ≥h/4π future coming into existence with the exchange of photon ∆E=hf energy transforming potential energy into the kinetic Eₖ=½mv² energy of electrons.
My explanation is that a photon is a quantum particle, but its mode of transmission is within waves. So even if it is observed to go through one of two slits, the carrying wave still goes through both slits. This wave with no particle passing through the other slit interferes with the portion on the wave that carried the particle through the first slit. So we still get the interfence pattern over the course of many individual particles. This is how I have always envisioned this phenomenon, and it removes a lot of the mystery and nonintuitiveness from the problem.
There's a field of photons that summons photons (particles) depending on a probability function (probably highly - if not only - influenciated by electromagnetic fields).
Is there any videos which show the effects of the double-slit experiment observed, and also unobserved? I've looked for videos that demonstrate both the interference pattern and the wave-function collapse, yet without luck! If the double-slit experiment were filmed, wouldn't that register as a form of observation, which would cause the WFC? Where exactly within or around the experiment, can't we secretly look? That if we observe, the wave-function collapses? If the WFC occurs when being observed, how is interference pattern also visible, as I think it was with this video? Anyway, just a few questions. Thanks!
we placing a screen is exactly what counts as an observation. we don't know whether light is particle or wave *in between* the slits and screen, but as soon as it hits the screen(observation happening), WFC occurs, and we see a single spot(in case of single photon)
You have to do the experiment in a vacuum to avoid spurious readings, you also have to limit the detected photons to a single frequency, otherwise you get photon splitting when it energizes e.g. oxygen molecules.
At 1:47 (as is at other places on video), term "arrive in phase" is not true. Interference occur much earlier than when "hitting" the screen. Do the same experiment with strong laser (doouble slit experiment), and make fog in the room - you will see that whole path from the slits to the walls is already interfered. So, no matter where you position your screen, interference occur.
Maybe the key to understanding another feature of the photon is an explanation for the seven peaks of the position graph with there being three symmetrical sets and the lone single central peak.
I still wonder how can you be so sure you can control a device to release just one photon at a time? Can you ever be sure about it? I mean, technology always has incertainties/inaccuracies, especially when doing something very very small (smaller than a photon is pretty hard to imagine).
hey it just struck me that you can calculate the length of the wave by measuring the distance between red stripes on the laser experiment when you were showing why there are black stripes, when waves are out of phase.
On wave particle duality, I've always held the view that light is in fact a wave and that there is no duality, but that it is the way that matter can only absorb light energy in discrete quanta ( or 'photons' ) that gives it the appearance of a particle. So, in the double slit experiment, this might explain why single 'photons', shot through 'one at a time', are more likely to get captured on the detector where the wave fronts constructively interfere.
My posit, is that the photons are riding the waves, rather than being the waves. I posit that all seemingly dual particle-wave entities are actually particles riding these same waves. Which is why we can see interference with single particles, because the waves are interfering with each other, and that particle is riding the interference. The waves propagate at C, and light, being massless is able to move at this maximum speed. If the waves could propagate faster than C I would expect the light particles to move that same speed. Alternatively it could be that the waves are light, and light is in no way a particle, and a "photon" is just a single wave pulse. I'm more inclined to believe this, than the idea that a particle with no mass can exist. One way or the other, I don't at all believe in the duality.
This "like a particle riding a wave" kind of explanation may be comfortable to believe, and it might go well with some experiments like this, but the thing is, you are just more inclined to believe something that you can imagine visually as well, rather than something that nobody can actually really comprehend. Sorry, it is not how it works, it cannot go that way like a photon speck thingy riding a wave thingy. It would just contradict to a lot of actual stuff... photons (and other particles) are really that kind of special snowflakes, and works such a manner that cannot be just explained with just regular specks and waves and whatnot one may find in the kitchen.
Székely Gergely "Sorry, it is not how it works, it cannot go that way like a photon speck thingy riding a wave thingy. It would just contradict to a lot of actual stuff..." Provide some examples please.
That is an interesting concept, at least for visualization... and it makes perfect sense, the interference would always be there and the photons would just mark it more and more on the screen until the pattern emerges. My question is: Where is the wave coming from? Its obviously not there all the time and it can have different lenght depending on the source used... so are you proposing its created in the source, at the same time the particle is created and the photon then rides it? IF so, isnt that just an analysis of the duality? Picturing the photon as a particle riding a wave if their existence is fundamentaly tied to each other sounds very much like waveparticle duality :D Just in different words.
+Youssef Mejri I can't even imagine a way to detect a single photon without disturbing / destroying it. I've heard this claim many times before that if you observe the single photons going through one slit or another that it again acts like a particle... I've also heard of people turning off the detectors and it continues on like a wave once again.... and further crazyness of keeping the data collection on but then later destroying the data, and the photons acting like waves still (crazy). Buy really, how can one observe a photon without actually converting it into a current? It isn't exactly like you can sense it's presence or something - can you?
+George Viaud The detector is literally sensing where the photon is hitting. It doesn't matter whether the photon is destroyed or not, because what matters is what it did before that. It's like shooting bullets at a target, it doesn't matter if the bullet is mangled or destroyed upon impact, we still know where he hit the target.
phiefer3 I think you're talking about sensors on the target plane and not at the slits? If so my question still stands, how can one observe a photon without disturbing it (or destroying it for that matter). Thank you for your interest in my question.
"how can one observe a photon without disturbing it (or destroying it for that matter)." As I said, you don't have to. It doesn't matter if it's destroyed or disturbed when it hits the target plane, that happens regardless. When the experiment is done with a constant beam that's still happening, and we're still "observing" the results in the same way, by the pattern on the target plane. The only point to this variation of the experiment is to see the results of a single photon at a time, ie a single photon hits the target plate, record where it hit, another photon hits, record where that one hit, etc. The purpose of the detector is simply to be sure that only one photon hit at a time (to ensure that there wasn't another photon for it to interfere with), as well as to record where it hit because we can't see it with our own eyes. Other than that, it's no different than the constant stream experiment, that could be done with the detector as well, we'd just get really high numbers for the number of photons hitting it and we'd generate a graph in addition to the visible results.
The distance between 2 bright spots Δx = Lλ/d, where L is the distance to the projector, λ is the wavelength of the incoming light, d is the distance between both slits. For the wavefunction of the photon ψ(x), Lλ/d is half the wavelength, so the wavenumber k = πd/Lλ. The form of ψ(x) = cos(πd*x/Lλ), where x=0 is at the position of the middle band
Not at all an expert, but from what I have learnt so far from YT suggests to me that light is more of a wave; a quantised wave i.e. what we call a 'photon' is only really a short pulse of a wave in the EM field. Imagine holding an infinite rope and just sending a few cycles through it, which will together form one pulse. That pulse will exhibit the characteristics of a wave, because, well, it IS a wave, but it will also behave like a particle, since it's not infinite.
@@ゾカリクゾ Yes, you are right, Photons can not be stpped. Actually, what I tried to say that it can be "trapped" by a field of force oscilating in a higher frequency then it. But this is what I understood about fields of particles. :-)
@@ゾカリクゾ I think photons are particles interact with a kind of barrier which avoids to travel in a speed limited. What do you think about quantum vacuum interaction? :-)
still looking through youtube for a real life filmed (no funny animation) experiment showing the breakdown of the interference pattern due to the introduction of observation and slit passage identification. seems I can't find that...
That's because it's not something that can be filmed. This paper describes and includes data from a real world delayed choice quantum eraser experiment: arxiv.org/abs/quant-ph/9903047v1 Don't let the math equations scare you, just ignore them for now as they are not required for understanding how the experiment is conducted. The results on page 4 are as close as you will probably get to "seeing" the change.
I think it’s awesome with experiments that have to do with discoveries about the atoms or with the double slit experiment, we are making “discoveries” about the photon or atom, but what we really are doing is making assumptions on what the thing is SOLELY based on how it interacts with other things. I think it’s awesome because we see how the model of the atom has changed over time based on what observations were made concerning how things interacted with eachother, but never being able to just use a microscope or have some sort of super precise amazing measuring device that doesn’t interfere with the system at all.
What if the light photons are actually particles, but they are "riding" on a "background wave" that is everywhere at all times? We think we are seeing light as a wave when the particles are not being fired one-by-one, but when we do fire them one-by-one they still behave like a wave... so maybe it's not that the particles are behaving like a wave, maybe the "background wave" is what allows the particles to move in the first place. The double slits break up the "background wave" that the particles are "riding" on, causing the interference pattern over time...
Niclas Kupper The Michelson-Morley experiment posited the Aether to be a medium a photon would have to travel “through”, where as what the OP is wondering is does the photon travel “on” a wave. Taking this thought a little further, in the instant a photon (can be electron as well) is generated, a correlated wave forms instantly for that photon to travel on. A better way to explain this is the wave becomes the instant roadmap of all possible paths (meaning the entire wave pattern in all of space-time is established instantly) the photon can travel and if direction is accounted for, the particle would have a specific predetermined path at any point on the one wave boundary (almost like how a surfer rides a wave). If the wave itself is instant across all possible paths in space-time it may explain quantum entanglement as the particles full path is entirely predetermined by the wave therefore measuring one of the entangled particles, regardless of distance between particles, would instantly reveal the measurement of the other particle. Or taking away the instant characteristic (and dismissing QE all together) the wave may very well travel at the same speed as the particle (or other way around) just as the same example of a surfer riding a wave and instead of many waves existing in a field, the wave may be just one wave cycle emanating from the source pushing the particle just like a surfer riding one wave and no other wave existing except for other surfers. There has to be something going on where the particle is being informed by a wave as to its destination. It makes no practical sense to take the easy/lazy way of accepting a particle is also a wave just because no other answers have been put forward. It seems quite obvious to me the particle is separate to a wave and only when dealing with direction does the particle then behave as a wave and as the photon generator is in a fixed position, the wave is obviously fixed from that position as well so the particle is forced in a regular pattern. Interested to hear what you think. One thing I have thought is the photon may be the physical stopping/collapsing point of the wave’s energy in collision with something else following a kind of uncertainty principle of its own.
I've heard that if you set a detector to observe which of the two slits the photon goes through the pattern you see is what you would expect from a particle. Do you know if this is true? Because that's what I thought was the most amazing result of this experiment, but it would seem unreasonable to believe that if it's not actually true.
***** So basically it sounds to me that you are saying that it doesn't matter if you observe the passing of photons at the double slit, or between the double slit and the detector, because in either case the photons will behave as particles. The easiest explanation being that photons travel back in time in order to determine how they will behave. Is that what you are saying?
what ? no... it doesn't need to travel back in time to know where to hit, its just mathematics. the wave can be seen as the probability of places where the photon will hit more and less often. as you could see in the video, you only see the pattern when you add up the results, but where they hit is pretty much random, its just that there is places where the probability to impact are higher.
3:01 does that graph mean that one single photons were detected in different locations on the director simultaneously? Or single photons ended up in different locations on the director during the second?
I think single photons ended up in different locations as per Heisenberg's uncertainty principle because, if one photon could end up in multiple places, I think experimenters would have noticed by now.
@@R4J4N No one knows yet, it is a conundrum in Quantum universe. Because of this experiment, let's just accept that light is both particle and wave and neither.
Option 1, is all things appear to be spinning and rotating: Galaxies, solar systems, suns, planets, electrons: it is reasonable to believe that electrons and photons have a spin. So if you shoot a spinning object at a point the spinning object will miss that point (simple baseball spin). If the spin is the only variable and has only certain frequencies they would end in a pattern. Option 2, all objects until we can no longer keep measuring smaller items have been made of smaller items, so it is reasonable to believe that even the smallest items we have been able to measure have made up larger things (excluding quarks, leptons, bosons, gluons, photons). One could reasonably believe that even these subatomic particles could be made up of multiple smaller particles that we currently are not able to measure and inside of the subatomic particles the smaller particles could have a spin and hence affect the pattern that may be produced when shot towards a single point. Just a thought
It actually makes sense, if an electron can only have a definite location when observed, this effect would act on the photon as well, making sure it isn't in its wave state and preventing it from acting like a wave at all. Effectively making it a particle when observed, and a wave when not.
if you make ripples in water, you have a wave, but water is still clearly made from particles, you would say that the wave is standing in a medium of water, similarly, couldn't one say that light is a wave standing in a medium of photons?
I am not a physicist but in the case of water, the wave passes through the medium yet with light the photons are the wave itself passing through empty space. Light is the wave itself, the movement and not the medium. The photon is like a single wavy thing that waves around idk but it is not the same.
it really seems to me as if the wave is made of water, if you would do the same to empty space as you would do to water to create waves, then no wave is formed, because the wave is made out of the water, if it would only pass trough water, then we should be able to create the same effect without any matter to move the wave trough and the wave itself should still exist in empty space
+Nienke Fleur Luchtmeijer but the water does not move per se through a wave. Gravity ignored, if you move your hose up and down, the final result might look like a wave but actually every molecule moves in a straight line and the wave exist as an illusion because of the hose moving up and down. A photon, unlike a watermolecule is never at rest and always moves absolutely at the speed of light and it moves as a wave. The particle itself waves up and down so to speak whilst the beam of light does not. Water has to be shaken yet every molecule still folows a straight path and doesn't wave itself whilst photons don't move in a straight line and the beam of light doesn't have to be shaken to produce a wave since the wave of light is a different kind of wave than a waterwave.
What do you mean when you say light is waves? Waves of what? Next year I will learn about waves in school but from what I have heard I won't really learn the real nature of them, just a bunch of math. I know that sound waves are just molecules going back and forth pushing each other but what about about light waves?
sometimes the best questions are asked by the un-indoctrin... uh I mean un-educated people. Waves of what exactly, no one knows... ether.. Its simply a way of describing the phenomenon.
Each quantum-mechanical particle is a wave. A particle is not like a spherical ball as one would imagine it to be. A particle IS a wave. I don't understand why people make this so complicated. So the question of particle OR wave does not even make sense! A particle is a wave. Thus different particles can interfere with each other, and a single particle can interfere with itself -- because they all are waves.
subh1 you are right, i couldnt agree more, there's no particles, just waves. that's why wavefunction works. there's no any particle functions in QM. it is funny that physicist dont see this, and still call wave-particle duality to make simple things complicate and confuse everyone.
Charles Yu I think the photon must have a field which pass through both slits creating patterns which pulls the photon side to side. The field is undetectable just because is part of the structure of space and time, unless we hit the speed of light so, particle is a particle and wave is a wave, it is impossible one particle pass through both slits.
Charles Yu I think the confusion stems mostly from the phenomenon of wave function collapse, which is still less understood. But then, even after the collapse of the function has happened into one of the position eigenstates, it's still remains a wave (may be a highly localized one like a dirac-delta function, but it's still a wave). Also, in the non-relativistic QM one can still talk about a wave function for each "particle". But in light of QFT, there is actually a single wave function that encompasses all particles! So the "wave-particle duality" is really a vestige from the past (early 1900's) when QFT was not developed and quantum phenomena were less understood.
If you model the photon in terms of E-M fields, then something important becomes apparent. Let the E-field be aligned with the slit and the M-field perpendicular to the slit. The M-field experiences the magnetic permeability of the material, which is asymmetric due to the presence of the adjacent slit. Now, Maxwell's Equations come into play. One has to reckon the effect of the lopsided discontinuity in the magnetic permeability. The effect is to deflect the photon to the side. Note that a comparable calculation could be done for a beam of electrons, where the electrons are modeled in terms of Gauss's Law (spherically radial E-fields) and Ampere's Law (circularly symmetrical B-field disks). Even if the center of the Guassian sphere passes through one slit, the B-field will encounter an asymmetry due to the adjacent slit. Again, Maxwell's Equations would come into play, with Faraday's Law producing a lateral force to deflect the electron to one side.
Light is the summation of probability waves (Richard Feynman - Quantum Electrodynamics). The single photon doesn't pass through both slight, the photon's probability wave does, because the probability wave takes all possible paths. If no attempt is made to resolve the probability wave into a single path by attempting to determine which slit the photon went through, then the probability waves will interfere and the resulting resolved photons with create an interference pattern.
Looking over my notes, I came up with this new picture of a photon particle wave. Bit difficult to describe in words, but it is based on photons that can create positron electron pairs. Photons are a series of particles like stepping stones. At each stop the photon shoots out a positron crest in one direction, and an electron trough in the other. This LOOKS like a single complete wavelength. But it really is a photon turning into an electron positron pair, each springing out of the photon in the opposite direction of the other. So each wavelength is, photon in the node of the wave position, with a negative electron trough on one side and a positive positron crest on the other. Further the node between two wavelengths may be where an electron trough meets a positron crest = annihilation. This process would all be as quick as a quantum jump.
I don't think that we know what a photon is yet . If it was like a segment of radio wave then it will spread out in the x , and y dimensions as it travels though z A photon is to electrical magnetic waves --- as --- a smoke ring is to pressure waves It has something to do with standing waves and a resident with space and time .
re: "What happens when single photons of light " No. It is _not_ possible to create a single so-called "photon" ... you cannot even much less DEFINE the size of a photon let alone create a lone, sole 'photon' ...
+Glass Menagerie they are a noun though. Nouns, and even "things", do not have to be physical objects. An idea is a "thing", a word is a "thing", a question is a "thing", a name is a "thing" and even movement is a "thing". So yes, even waves are "things", even if they do not physically exist.
I still dont get how is it possible to know that you are creating what you call "a single photon". Wasnt light a wave in the first place? How can you make a particle like thing if light have a wave nature in the first place????
I'm not familiar with the specific equipment used in this video, but here is one possible method. Each photon has a discrete value of energy. If we know the frequency of the light emitted by the laser (which we do), we know how much energy each photon has (E=hf). Therefore if you aim the light at a detector and measure those discrete changes in energy as each photon hits, you know that a single photon is hitting.
Photomultipliers use a sort of "domino effect" of electrons to count each photon. When a photon hits the detector, it excites an electron or two on the detector. The photomultiplier uses a high voltage to accelerate the excited electrons to a high velocity, allowing them to excite even more electrons This process is continued until there is a high enough number of moving electrons (electric current) to be detected. That's why they're called "multipliers"; because they physically multiply the effect of each photon until it's enough to be detected.
If photons are interfering with each other after they go through the double slits, why doesn't the interference cause the photons to experience a "collapse of the wave function"? If the photons are interacting with each other, they should show up at the detector as random points with no banded wave pattern since the wave pattern has been wiped out by interference. .
@@FrankCoffman Interaction between particles is an entanglement, it's not yet an observation. When one wave interferes with itself after going through two slits, it's still just a wave for one particle, it doesn't interfere with another particle.
@@karlkarlsson9126~ "...it doesn't interfere with another particle." It's assumed that interference between photons does occur after they pass through the double slits. That's the accepted explanation for the double slit experiment when a banded pattern of photons appears on the barrier. The bands are supposed to indicate wave interference. But why doesn't interference wipe out the waves, causing the photon waves to collapse into random point particles? Also, how can photos interfere with each other -- "Since light itself does not have electric charge, one photon cannot directly interact with another photon. Instead, they just pass right through each other without being affected." So how can photons interfere with each other if they don't interact?
@@FrankCoffman It's the wave that interferes with itself, not the photons with each-other or with itself. It's not a photon yet until observed. So you have the answer is in your own question, there is no collapse because there is no particles interacting with each-other. In Quantum Mechanics there is no particles, only waves of probability using the Schrödinger's equation, so a particle is described by a wave function, and when two particles interact it's two waves interacting, they will share the same wave-function (entanglement). For waves to become particles and behave as particles they need to collapse, being observed. The end results in the double slit experiment showing the wave-interference is particles showing that they traveled as a wave but hit the screen and collapsed as particles.
ive heard in a lecture by Richard Feynman that light is defiantly a particle. the duality conundrum comes from us trying to explain the behavior in familiar terms but there is no doubt that light is a particle in every sense of the word. when we try to predict what happens we find that the same mathematics that describe waves gives a probability of where the particle will go. we cant say with certainty that the particle will travel a defined path, but we can say with a great deal of accuracy that given a large enough sample you will see signs of interference showing up.
he has provided incomplete information about devices used in this experiments. He says about Photo-multiplier which detect the photon and Frequency counter which counts photons per second. how the position of photon found and plotted graph?. which device is used here?
Vijayan T good question. i saw your Quantum Eraser video. but do you know typically how to record the photon location on the screen? although we are sure photons definitely just cohere with itself, but it will still be useful to know how the device did it.
He's putting the photomultiplier in one position, measuring for a while, then shifting the photomultiplier to the next position. This way he gets a photon count for each position, but it's important he measure the same way at each position.
“Dim light “is not the same as a “single photon” what you just did with your graph over time is the same as a long exposure in photography. Prove that a dim /faint light source turns it into a object (particle)
Here is a scary thought -- what if the single photon interference pattern is in fact a superposition of all possible outcomes and it effectivelt interferes with istelf through its own superposition???
There is no such thing as single photon. Boy, I wish to make "anti-veritasium" (latin: veritaserum) TH-cam channel. Or "Mendacium" channel. "The channel of lie". :D
well like he says a photon isn't a particle. why than does he think he can produce a single discreet "one" of them? there is a contradiction there.. the duality conscious mind doesn't see reality as one whole.. instead it believes finite things to exist.
Because you can create single photons. You can divide light down into its smallest element, but no farther. If you try to send less than one photon, you send nothing. You can measure which slit the single photon is going through. And if you do so, they stop acting like waves, and start acting like particles. You can count the single photons in a detector.
Now, try to detect which slit the photon goes through. This is when the experiment becomes truly mind blowing.
Joshua Nicholls when you do that, you no longer see the interference pattern.
+Charles Yu (Chao) Uncertainty principle! Right?
+AlphaMineron Close, but rather it's the collapse of the photon's wave function. One of the fundamental quantum mechanical laws is that upon measuring a quantum system such as photon passing through a slit, the photon's probabilistic wave function "collapses" to keep producing the same result measured previously...nobody knows why and we just accept it as fact.
Look up the quantum eraser experiment. They use a crystal to split the photons into two identical (and entangled) photons. One is sent to the detector, one is sent to a series of mirrors. The mirrors 50% of the time lead to detectors that will tell which slit the photon went through, and the other 50% of the time it destroys the information.
The second set of detectors is placed far enough away that the photons hit the main detector before the second photon ever hits the mirrors.
Even after all this, the photons that you can determine the slit it went through do not show an interference pattern, while the other photons, where you've destroyed the information, again show the interference pattern. It's as if one of the entangled particles goes back in time to say "hey, they figured us out! quick, be a particle!"
DaffyDaffyDaffy33322 I don't understand that experiment.
I think I need some time. I tried watching the PBS Space Time video on it but it's quite confusing.
When i was in 9th or 10th grade our teacher showed us the double slit experiment with a laser and we could see the interference pattern in the dark classroom. Now i feel really thankful that i had the opportunity to witness this live and become fascinated by science. Sadly i wasn't so aware of that when i was at school, but i think deep inside it helped to build up a fascination for physics and science in general.
Just because your teacher showed you something , It doesnt mean its true. Look at all this ANTI-TRUMP proaganda!
whereas I, a ninth-grade student at present, performed this experiment successfully at the science expo and got a D grade. 😅😅
@@majoris_roborionQuantum mechanics is very very under appreciated.
As much as I like the idea, I'm not sure "wavicle" is going to catch on.
Zak Hale definitely not..
Already did. It's a legit term :D
Xakimus Prime wacle?
Wave particle duality?
Jenny K Woah. I just looked it up and it was real
I had many thoughts and questions after seeing this video:
1. what is the size of each slit? how far apart the slits are individually? what is the size of photon or wave? at what distance the light generator is from slits? and how far is the sensor/receiver?
2. What if the each slit is closed alternatively?
3.what if there are more than two slits?
4. what if we place two photon guns at an angle to each other to fire photons through single slit and try different options?
5.what if we place two photon guns at an angle to each other to fire photons through double or more slit and try different options?
I hear you can get good slits on ebay, the instruments though....
I also ask what if "filter" and display were not parallel and flat?
@@fizzicist7678 i
Don't have answer to any of your questions
@@anti_gravitationalI wasn't asking any, so you are fine.
IIT Advanced wala banda ho tum
The best visual explanation of double slit experiment I have seen till date. Thanks Veritasium.
This is amazing knowing that one of the chapters we are taught in last year of high School (or a lesson) is so close to the Quantum Mechanics. I am 18 and I am happy that I could find out that my high Physics whether it was newtonian physics or any other branch... Believe me when I say "it was was astonishing!"
We spent close to two hours covering this topic in Physics today, this video contains everything that the teacher taught to us in two hours but in 6 minutes.
college is a scam
doubt it
@@LuisSierra42 should definitely be cheaper and often not as required
Yes but you need an in depth primer to fully understand this shorthand demo.
You're meant to write it down, think about it deeply. You really can't do that on TH-cam on the toilet.
I totally love what you're doing here. You're like the perfect mix of my physics and chemistry professor from High School. I've been wanting to re-visit this, and some of the other items you've touched on, just to refresh my memory, it has been 30 years since my last formal class. Thanks!
Your videos are outstanding: informative, engaging, educational and interesting. Thank you Derek!
Quantum Light (h) is a dualistic quantum particle that in the cosmic vacuum
can fly at a constant speed (c=1). In this movement, light uses its linear spin
and it does not produce electromagnetic waves. Light behaves like a corpuscular.
But light can behave like a wave if it uses its angular rotation (the torque required
to accelerate angularly around the axis of rotation). In this situation, the speed
of the light is faster than the constant. The speed is c>1.
This situation is explained by Lorentz transformations.
The problem is that we do not know the geometric shape of the light quantum.
I have a great word. Golfbal. In Dutch 'golf' besides the sport is also the proper translation of the term wave. We also don't use spaces when we use word combinations so golfbal would be a 'golf ball' or literally translated 'wave ball'. I always joke around with this at my university since its quite funny if you are Dutch.
Niet echt.
Robert Fennis It's a quite funny double meaning yeah. But it'd not be a great physics term, unless you can show that photons are shaped like a ball...
"Golfbal" Ik vind hem best goed, ook al heeft het eigenlijk niks met een echte golfbal te maken
nee maar dat is juist de grap. Twee woorden die samen niets meer met het origineel temaken hebben.
Yes! It shall be called the Golfbal effect!
Derek, This is a very interesting topic. I hope you do more videos on it. I summarize what's going on this way: "things travel as waves, they appear as particles". It's true for all things - just not very noticeable for big things which are collections of a bunch of small things travelling as waves and appearing as particles. You'll notice that with mirrors and beam splitters and slits and screens you can get the wave to bend, split, or pop. When it pops - that's the wave manifesting as a particle. I think you can get deeper insight into this by asking yourself - "why is it that fiddling with the wave sometimes makes it pop, and sometimes not?" What is the boundary of fiddling that just under it the wave continues - although perhaps bent - and just above that amount of fiddling and it pops. What are the factors that determine how much fiddling can happen before popping occurs. Also when I see a wave pop - and you watch the same thing - do you see it pop to the same place? I've never seen or read about experiments along this line. If you can - can you do some experiments along those lines. I don't have access to equipment to do it myself.
*EVERY QUANTUM THEORY IS WRONG*
I said this, and I will say it again...
A photon is not a particle with wavelike properties. It's a wave, that localizes it's energy upon interaction due to energy transfer.
Like a cloud shooting lightning. Which turns it into what we OBSERVE as a particle.
It's not both at the same time, and it's not at multiple places at the same time, neither is energy transfer that's faster than light possible through entanglement. NEITHER is the schrodingers cat experiment's superposition broken by us looking into the box...
All we know is that (once measured/observed) the "wavefunction" collapses and we get a point.
But we have been concluding wrongly about the origin properties of quantum particles.
For a quantum particle to be measure there has to INEVITABLY be an energy transfer between the quantum particle and the measurement apparatus. THIS is where the quantum particle suddenly appears to us as a particle... But it was never a particle. It just localized its energy when measured.
The nature of quantum particles has fooled us to believe they are particles.. They were never particles..
NOT quantum particles...
They are quantum *WAVES*
or rather: quantum *excitations.*
Mark my words, for in the future you might learn this in some video. After we finally figure out I wad right.
The measurement system breaks the "quantum wave" into a particle due to the interaction between them..
@randomshittutorials There's a good bit of questions I have but first do you know if they have done experiments or anything to show if our eyes observing from a certain potion or something collapses the waveform too? I ponder that because wouldn't our eyes cause some sort of energy transfer too collapsing the waveform. If that's true then I completely agree with all you've said and I'd honestly like to message some more. I've been deep in thought about similar topics
@@randomshittutorialsI do keep having this sense of wonder “is anybody thinking, hey, I don’t think we have this correct.”
I feel like we are at the tail end of a super difficult sudoku puzzle and realizing we got it wrong but no one wants to start over
@@Yellow-Viridian834 Sorry to keep you hanging so long. I am still convinced my deduction based on countless information is true.
The thing is, our eyes are the same as the measurement apparatus. The photons hit specialised cells, that turn the interaction between the photo and our cell into electrical signals we can process.
For this to happen, the photons HAVE to interact with our cells, which means, by definition, there is an energy transfer, just like with the measurement apparatus.
The problem is, that our eyes and brain aren't precise enough to measure a single photon.. This is why we use the experimental setup which documents the results on a piece of flat reactive paper.
But, yeah, our eyes would also collapse the wave function by that logic. It does so all the time. It's why you can read this message.
@@josiaphus Well we know it's not complete. We say "not complete" because we've proven that what we know works 99,9% of the time. It's too much proof to say it's wrong, but it surely is incomplete, and I believe most people look at this subject with scepticism, but most also understand that due to the unintuitive nature of these physics, yapping like drunk idiots won't resolve anything. And most who think they know, are wrong.
I am almost surely also wrong, but I still believe that my deduction is SO MUCH better than this, being at multiple places at once BS. Or it being a particle AND a wave.
It might be due to my caveman brain, but I have to this day only found ONE experiment that seems to defy my idea in a way that makes sense.
It was a variation of the double slit experiment, with mirrors that had a chance to let the photon through or not. Photons seem to be able to be at multiple places at the same time, as it reverted back to the old path when the other one became unavailable, even if it was already past a certain point of seemingly no return.
This throws dirt in my visualization of what I thought a probability wave is... It seems to be more than only a wave.
But at that point I'm just yapping. I have no clue why it does what it does.. I hope the great scientists of the world will give us new answers.
Till then I still don't believe they are a particle and a wave at the same time. But maybe due to the nature of a wave, it can be at multiple places at the same time. It depends on how you define a wave's location..
What I will still push is that, iquantum particle, are not particles, they are waves, who act like particles upon interaction.
Long before I ever heard of physics, my mother had started me on a quest to figure out magnetism. By 5th grade (1963-1964) I was working on self-sustaining experiments. The reason a photon acts as a wave and a particle? the particle forms from the wave. When a wave 'breaks, a string remains with + and - ends. They are attracted to each other, and we come up with the snake eating its tail, but in this case, we have energy passing through energy. The only way for this to work is for a vortex in the center to form, much like a figure '8' or a strand of DNA.
I like how you explained the waves interference. It was Very helpful and helped me understanding that a little better.
Turn the light source on and off after each "photon"
I understood the experiment for the first time. Bravo!
4:20 🎶WHAT IS LIGHT, BOSONS DON'T HURT ME, DON'T HURT ME, NO MORE🎶
lol, nice timing
I don't know, maybe I do
Well done 🎯 This visualization helped to clear up the basics of the timing & phase *better* than *any* other video/explanation. 🚀👊🍸
I prefer a “partywave”, especially when we’re dealing with colored lights (and music)
Oh yeah
Nice
hahaha
I literally did the slit experiment in my room using paper, cardboard, and a laser yesterday.
It was absolutely beautiful and mind-blowing!! Highly recommend.
I think the answer is quite simple but I could be wrong. Everything is made of the same energy when you get down to the quantom levels. We just experience them as different wavelengths and frequencies. When you do the double slit experiment with multiple electrons you see the wave interference patterns from doing a unrestricted observation. By shooting "one electron" at a time the only thing you are doing is changing the rate of speed at which the wave is passing through both slits, thus you are getting the same interference pattern over a longer time, but when you put the detector up and restrict your observation parameters to "50%" or (one slit or the other) that's the only result you will see is one or the other because you have narrowed the observation results from an open ended observation to a (one slit or the other restricted one). It's like narrowing your experiment parameters down to only 2 frequencies of light, only seeing the red and yellow frequencies of light but then asking but why am I not seeing the entire rainbow? It's because their act of specifically only measuring one slit or the other has resulted in them only seeing one slit or the other. By narrowing their observation window they have narrowed their results. Explain how I'm wrong @Vertasium
I think you must first prove that there is such thing as "single photon" and you are actually tracking it. As far as I'm concerned, you made the same experiment, with lower intensity light, and the pattern is just less visible... Actually I would be shocked if you got anything different, that would break the most fundamental idea of the field as something continuous in space. What you did is just lowering of the field to the point where your measurement system struggle, nothing fundamentally different... My vision is that what we call "photon" is just property of the field, and the only way to be shocked is to assume something wrong in the first place - that it's a "particle" and you can "track" it.
Exactly, there are no 'particles'.
I know it's been two years since you posted but i am just now seeing this video. After reading tons of comments i was feeling frustrated until i came across yours. I feel like you perfectly expressed what i was thinking as i watched this video.
@@dreamdiction There are also no waves either. There is only a quantum mechanical state vector for the light and a measurment. The thing is coherent sources have a very particular state vector withi is not a real "one photon state". I would like to know what happens with SINGLE PHOTON SOURCES. This is. sources that generate photons with a single photon quantum state (not a coherent state), or in other words, an eigenstate of the fock space with n=1. These states are not superpositions (as coherent states are, and do not even have oscillating magnetic or electric fields). Single photon sources exists and there is much interest in them with applications in quantum computing hardware. But they are really state-of-the--art hardware. I'd like to see what happens with the interference pattern when one of those are used.
@@Brucebod If you read some (or rather a lot) of quantum mechanics you may understand what is really going on here. The important part is the quantum description of the light as a state vector. It really is neither a wave nor a particle. Is a quantum object.
Also you can't deny the "particle" aspect of the experiment. You detect INDIVIDUAL photons after all. If you have any doubts, just go learn some quantum mechanics.
@@PsiSubDiego "If you have any doubts, just go learn some quantum mechanics." Aggh, I'm trying, I'm trying. I guess i am frustrated because I still cannot understand something that i _really_ want to understand. I will keep trying, tho.
I would love to see a video that discounts all the other possible explanations for the same result being obtained whether particles are fire one at a time or sumultaneously. It seems a pretty big leap (a quantum one in fact) to arrive at a quantum explanation, without first discussing the many possibilities that mechanical physics offers.
I agree. What if the entry-point detector that, when activated, apparently makes the photons appear (as classical physics would have us expect) as dots, rather than as waves, on the screen, were somehow 'processing' the photon, changing its physical properties?
When you have 2 or more paths you add "probability amplitudes". which are just arrows that turn like hands on a clock very fast, and stop depending on the time light takes to go those paths. When there's one slit open there is only 1 arrow. When 2 slits open there are 2 arrows. Any path to any point on the screen where the arrows point in mostly the same direction has a band of light, any path to any point where they point in opposite directions there is no light. Simple as that. Goofy as that.
3:49 Could you say that it travels as a wave, but interacts at a point? I feel like this is a pretty intuitive explanation, but I've never heard it said this way. The explanation that makes it seem mysterious seems to always be preferred. It travels as a wave, and collapses to a point when it interacts.
I think that when a single "photon" is emitted by one accelerated electron is, as Maxwell says, an emspherical em perturbation wave in the 3d space; when this wave is passes through a single or double slit is diffracted but is still an em wave that become a photon oly when interacting with the screen. This is also a "measurement". Nice video.
It's so good to see what I study in high school, in reality. It's like you're in sync with our physics book 😂 your vids are great
"We now know that they are just waves. They only appear as particles" - Sean Carroll
Yeah well. Sean Carroll sometimes tends to oversimplifies things for his divulgations talks. There are just waves, or to be precise quantum mechanical waves, which is quite different from electromagnetic waves from Maxwell's equations.
@@PsiSubDiego he favors the spherical cow approach to explanations.
@@codyramseur It seems to me calling quantum mechanical objects "just waves" is more of a spherical cow than acknowledging that they are neither (as quantum mechanical equations and experiments clearly show). Or are you suggesting there is something wrong about tha QM description?
Great video. Great explanation. The best I found on TH-cam.
Now there is a theory that photon IS a particle but space is the wave behavior, so even if you shoot one single photon throught the slits, the photon will follow the space wave. Like a boat on water it will go straight but follows the wave of the ocean. Maybe you need to go at the speed of light to behave like a wave. If you could shoot me at the speed of light like a particle throught a giant slit, I, the particle, would follow the wave of space making me look both like a particle and a wave.
interesting
+bob roger A photon ISN'T a particle it's closer to a form magnetism in fact, like gravity.
Tesla was closer than Einstein and the Quantum clowns. One could say everything is magnetism and yes atoms themselves. Then there is the aether or counter space...
+bob roger I like your thinky thoughts. Prime in my mind when considering light's properties is "what the heck is waving?". We understand how waves move through water, waves through air is what we call sound, what is the MEDIUM which is conducting electrical waves? The wavy space idea is interesting...
+bob roger What about electrons that exhibit wave like behavior? They aren't massless so they cannot travel at the speed of light of course they certainly are fast. At what point does matter cease acting like a wave? I don't think the theory you're talking about is all there. :/
After thinking about the results of the recent "gravitational waves" experiment, and watching this video, I arrived at the same conclusion as the op above.
I came up with the following analogy: Think of a particle of dust, or sand, inside the vast ocean. On the very top layer of the ocean, one could observe the sheer force and violence of the waves. However, once you dive in, deep, those forces no longer apply in the same manner, though, they are there.
A a particle of dust, sand, or what have you, will move in a wavy pattern as the forces of the ocean propagate and reach the particle's destination, each time giving you a slight push up or down, and foward.
If we think of light in this manner, where particle of photons are carried by the gravitational waves of the universe, then we could explain their wavy pattern.
This morning I woke up with a question: could we expect photons to appear at a set percentage in a given spot?
In other words, could we expect photons to be at a given place with an expected percentage of probability?
Please, any one who might have the answer, I'll much appreciate it. Thank you.
Very interesting! Well done! Every 13 year old needs to see this as well as your other videos. Huge thanks!
This channel made me a fan of the double slit experiment
Young must be blessing Veritasium
I've always thought that light was particles that move as a wave. Much like with sound, there are points of high and low density in the concentration of particles. The particles themselves are also moving forward in the same direction as the wave, and it is the incredible speed of the particles that make it difficult to differentiate between the types of movement. Since photons move at slightly less than C, there is still enough of a difference between the two types of movement (linear and wave) that this doesn't seem impossible. The information represented by the wave can translate at exactly C, while the photons themselves are slightly limited by the energy representing an infinitesimally small mass.
I'm not sure I've explained this very well, but am I entirely wrong in the way I understand this? It sounds like you're saying they couldn't possibly exist in both states at the same time, but it still doesn't seem unlikely. A wave is just a method of travel, a contracting and separating of particles. It's hard to visualize something that both moves forward and has an elasticity of speed that would allow for wave propogation, but I'm nowhere near adept enough with mathematics to validate or disprove the possibility.
I hope I haven't taken too much of your time with an inane question. If you have read this, I appreciate as much as that. Keep making awesome videos, Derek; As much as I enjoy other science related channels I never learn as much with Destin or Michael as I do from you.
Light does not travel in particles that move like a wave. That’s an incorrect assumption.
@@karthik.b1309 That's a great explanation thank you.
@@karthik.b1309 Yes, I didn't die or anything not for lack of trying
"Wave-icle" would be a great name for a sister channel to Veritasium!
Wait a sec...
"I can't possibly block all of the light"
and
"It's counting a single photon at a time"
Huh???
by light he meant "electromagnetic waves", long wavelength(low energy) waves like radio waves are hard to block, but higher energy waves like visible light, can be blocked and measured to the level of photons.
The photomultiplier has sensitivity to single photons strikes, which is how it can read out that the background rate is 4 or 5 of them per second. They don't all hit at exactly the same time or same place, and most of them probably did not pass through the slits, but hit the photomultiplier from other angles: at this low rate, they will not have significantly interfered with each other in the experiment. You don't need to reduce the background rate to zero to see (eventually) that some regions have significantly higher rates above background than others.
there are no photons, then there would be a red green and blue photon
they part of the eletromagnetic spectrum
light is just a free form of energy with a certain wavelenth or charge
The very definition of "background noise". That's why the experiment has to sum up a large number of individual measurements over time.
@Plague Doctor There's no contradiction in the statements you highlighted.
I thought about this a lot when going to university and also afterwards.
Clearly from the double slit experiment (involving multiple photons through both slits) the resulting interference pattern appears to be a function of photons constructively and/or destructively interfering with each other.
However, clearly from the double slit experiment (involving single photons through one slit) the resulting interference strongly suggests that individual photons constructively and/or destructively interfere with themselves.
So, that suggests another particle is present.
Above, I mentioned that I thought about this a lot when going to university and also afterwards; and what I concluded was this . . . .
Since quantum field theory (QFT) stipulates that every particle has its own antiparticle, provided that particle is charged, it introduces the possibility of an anti-photon.
QFT also describes what properties each antiparticle will have from a space-time perspective within the context of (when compared to the matter particle) equal mass/spin and opposite charge.
Since most photons are not charged (at least as far as we can detect) one interpretation of the QFT that follows is that no anti-photon exists.
However that is only one interpretation of QFT as it applies to photon particles; itself reliant upon the assumption that we know everything there is to know about light; in all the dimensions it may exist.
Another interpretation of QFT as it applies to photon particles is that (despite the photon apparently possessing no charge) one can still - by retaining mass/spin and substituting charge polarities - employ the construct of the anti-proton; particularly since this seems to do very little to the photon.
For the most part, respected sections of the scientific community accept that anti-photons exist.
So, given the above, uncharged photons can be their own anti-particle; or anti-photon.
Furthermore, charged photons also have their own anti-particle; or anti-photon.
Many particles are their own antiparticles, such as force carriers like Gluons, Z boson, and Photons; some of which modulate and/or interact with nuclear and electromagnetic forces.
So, the above discussion provides for a simplistic insight into how/why the double slit experiment that seemingly involves single photons fired through one slit, still results in a constructive/destructive interference pattern that resembles what happens when multiple photons are fired through double slits and interfere with themselves.
Now, how (i) the Pauli exclusion principle, (ii) the fact that, since photons can be their own anti-particle in ways that mean that photon numbers are (unlike Leptons/Quarks) not conserved, (iii) it is considered that photons can annihilate themselves, (iv) any relativistic and/or multi-dimensional considerations apply to observed results . . . . .
Remains to be seen and is outside of the scope of this discussion
In any regards, I have always thought that the consideration of the above (particularly the existence of photon and anti-photon pairs {whether they are the same particle or not} within the dimensions we do and do not perceive) is the best starting point for trying to understand the dilemma of the double slit experiment.
Not in the least, as the existence of photon and anti-photon pairs provides for (at least) a starting point that seems to have some possibility of explaining how interference patterns requiring more than one particle are still observed when (it seems that) only one particle is fired through a slit.
Never say never, as (in a similar way that Planc Stars are neither proven or disproven) I still think it is not perfectly clear whether or not a star can exist that is so large and massive (think 1 billion times the distance of our solar system) that when/if a component of its inner core collapses - despite it later creating a black hole - the subsequent recoil force is not enough blow the entire outer shell away and into a supernova; leaving an inner spherical radius that is slowly eaten away whilst also bombarded by the energy of the black hole’s accretion disk and other ejections.
Any updates on your conclusion. Any neew information. I was operating under the conclusion that photons are packets of energy that warp space around it. one side is pushing space away from energy and the other pushing into itself. I think of photons as particles that are balanced by space
Thankyou Derek! This is the first time that anyone has actually explained what we are seeing in the double slit experiment. Yes many people explain that what we are seeing is an 'interference' pattern but they don't explain how the troughs of the 'waves' (or should I say 'wavicles') are caused by the extra distance that light from one slit travelling at an angle to light from the other slit has to travel and how the peaks are caused by light from both slits coming together from the same angle so that the light from each slit travels the same distance. We can understand this if we consider light to consist of waves. But when the same experiment is done with single photons - then it gets weird.... The same interference occurs, so a photon is actually a wave as well as a particle? Hmmm!
No. :-)
The confusion stems from the assumption that electromagnetic waves are quantized. They are not. Photons are interactions between atoms and the electromagnetic field. That interaction is quantized. Once an electromagnetic wave propagates, it can have any intensity you want: a billion photons, or one tenth of a photon, it does not matter. The wave properties remain, so that interference is still happening at a slit.
There is no photon traveling as a tiny wavelet along the laser line. It is the electromagnetic field that is supporting a coherent wave from source to target, where we let it interact with sensors.
As an electrical engineer with PE stamps in 3 states I have to say bravo! Wowee Exceptional job!
There are no real "particles". Particles are really theoretical center points of complex electromagnetic wave fields. They represent the center of peek magnitude and the field's energy signature at the point of observation. These "particles" have huge extended fields and it is the extended field that passes through the second slit, that splits the single photon filed and causes interference 'with itself'.
relaxxxrrr Does it represent the peak? If we measure, we get a single position, like a particle. But that position doesn't need to be at the peak, that's only the most likely part. So I don't think it's fair to say which specific part of the wave is a particle until after you've measured it, but then the wave is gone...
mdilligaf Are we really measuring a single position, like a particle? "Particles" are at least 10 thousand times smaller than an atom. Is the equipment in the video really counting single photons or is there some misinformation going on. Look at the resolution of the sensor, tenths of millimeters is nowhere near "particle" resolution. Wavelengths of light are a million times smaller than that.
Observation of the quantum world is a real problem, I think the best resolution we can ever hope for is no smaller than an atom. A photon or any particle striking an atom is observed as an increase in energy of that atom. The exact position that a "particle" collided with an atom can probably never be known. The dot resolution of the experiment in this video is trillions of times larger than any "particle" accuracy.
"At the smallest scales there are no objects, only relationships" - Greydon Square
You don't need high spatial resolution to measure single particle interference. If you want to make sure it's single particles, the important thing is the time between events. If there's one count every few seconds, then you're probably counting single particles. The detector needs to be only small enough to distinguish the maxima. It doesn't matter if millions of particles fit in one 'pixel', as long as there is only one.
relaxxxrrr In case you're interested in measuring positions with high resolutions (smaller than the size of atoms, though that's a vague concept). The scanneling-tunneling microscope can already do that. It works with piezo crystals (for moving tiny amounts) and tunneling (to measure distance precisely). Has little to do with this experiment, but since you talked about spatial resolution...
relaxxxrrr When the wave function of a "particle" interacts with the detector screen, a phenomenon called "wave function collapse" happens, in which the function "collapses" into one of the position eigenstates, and dislodges an electron on the surface of the detector in order to create a "spot". But it still remains a wave even after the wave function has collapsed (may be a highly localized one like a dirac-delta function, but it's still a wave). So yes, you are right.
Typically in non-relativistic QM you have one wave for each "particle". So the right statement is "a particle IS a wave". But of course in light of QFT, there is actually a single wave function that encompasses all particles!
The "wave-particle duality" is really a vestige from the past (early 1900's) when QFT was not developed and quantum phenomena were less understood.
If I had you as my teacher , I would have been a topper
Wanna be my topper?
+Baghuul huehuehue
Poor choice of words, my frend...
One explanation is that light goes through both slits as a wave with probabilistic uncertain ∆×∆pᵪ≥h/4π future coming into existence with the exchange of photon ∆E=hf energy transforming potential energy into the kinetic Eₖ=½mv² energy of electrons.
My explanation is that a photon is a quantum particle, but its mode of transmission is within waves. So even if it is observed to go through one of two slits, the carrying wave still goes through both slits. This wave with no particle passing through the other slit interferes with the portion on the wave that carried the particle through the first slit. So we still get the interfence pattern over the course of many individual particles. This is how I have always envisioned this phenomenon, and it removes a lot of the mystery and nonintuitiveness from the problem.
There's a field of photons that summons photons (particles) depending on a probability function (probably highly - if not only - influenciated by electromagnetic fields).
Photons are electromagnetic fields, quantized. They are the same thing.
Is there any videos which show the effects of the double-slit experiment observed, and also unobserved?
I've looked for videos that demonstrate both the interference pattern and the wave-function collapse, yet without luck!
If the double-slit experiment were filmed, wouldn't that register as a form of observation, which would cause the WFC?
Where exactly within or around the experiment, can't we secretly look? That if we observe, the wave-function collapses?
If the WFC occurs when being observed, how is interference pattern also visible, as I think it was with this video?
Anyway, just a few questions. Thanks!
we placing a screen is exactly what counts as an observation.
we don't know whether light is particle or wave *in between* the slits and screen, but as soon as it hits the screen(observation happening), WFC occurs, and we see a single spot(in case of single photon)
You have to do the experiment in a vacuum to avoid spurious readings, you also have to limit the detected photons to a single frequency, otherwise you get photon splitting when it energizes e.g. oxygen molecules.
Yes, all sorts of enhancements improve the quality of the experiment, but not the quantum behavior that it demonstrates.
Wouldn't change anything !! As all the photons are traveling in the same medium
At 1:47 (as is at other places on video), term "arrive in phase" is not true. Interference occur much earlier than when "hitting" the screen. Do the same experiment with strong laser (doouble slit experiment), and make fog in the room - you will see that whole path from the slits to the walls is already interfered. So, no matter where you position your screen, interference occur.
Maybe the key to understanding another feature of the photon is an explanation for the seven peaks of the position graph with there being three symmetrical sets and the lone single central peak.
I still wonder how can you be so sure you can control a device to release just one photon at a time? Can you ever be sure about it? I mean, technology always has incertainties/inaccuracies, especially when doing something very very small (smaller than a photon is pretty hard to imagine).
hey it just struck me that you can calculate the length of the wave by measuring the distance between red stripes on the laser experiment when you were showing why there are black stripes, when waves are out of phase.
Bob Troller great!
This is correct! Bigger wavelengths correspond to larger gaps.
What if light was alive?
Isn't it?
What is light *is* life?
On wave particle duality, I've always held the view that light is in fact a wave and that there is no duality, but that it is the way that matter can only absorb light energy in discrete quanta ( or 'photons' ) that gives it the appearance of a particle. So, in the double slit experiment, this might explain why single 'photons', shot through 'one at a time', are more likely to get captured on the detector where the wave fronts constructively interfere.
How on Earth I just discover this channel now? I should have seen this waaaayyyy before!
Particle or Wave:
Porque no las dos
My posit, is that the photons are riding the waves, rather than being the waves. I posit that all seemingly dual particle-wave entities are actually particles riding these same waves. Which is why we can see interference with single particles, because the waves are interfering with each other, and that particle is riding the interference. The waves propagate at C, and light, being massless is able to move at this maximum speed. If the waves could propagate faster than C I would expect the light particles to move that same speed.
Alternatively it could be that the waves are light, and light is in no way a particle, and a "photon" is just a single wave pulse. I'm more inclined to believe this, than the idea that a particle with no mass can exist. One way or the other, I don't at all believe in the duality.
This "like a particle riding a wave" kind of explanation may be comfortable to believe, and it might go well with some experiments like this, but the thing is, you are just more inclined to believe something that you can imagine visually as well, rather than something that nobody can actually really comprehend. Sorry, it is not how it works, it cannot go that way like a photon speck thingy riding a wave thingy. It would just contradict to a lot of actual stuff... photons (and other particles) are really that kind of special snowflakes, and works such a manner that cannot be just explained with just regular specks and waves and whatnot one may find in the kitchen.
Székely Gergely
"Sorry, it is not how it works, it cannot go that way like a photon speck thingy riding a wave thingy. It would just contradict to a lot of actual stuff..."
Provide some examples please.
That is an interesting concept, at least for visualization... and it makes perfect sense, the interference would always be there and the photons would just mark it more and more on the screen until the pattern emerges.
My question is: Where is the wave coming from? Its obviously not there all the time and it can have different lenght depending on the source used... so are you proposing its created in the source, at the same time the particle is created and the photon then rides it? IF so, isnt that just an analysis of the duality? Picturing the photon as a particle riding a wave if their existence is fundamentaly tied to each other sounds very much like waveparticle duality :D Just in different words.
Petr Novák
Check out Pilot Wave theory, it's recently caught attention, and it fits perfectly with what I was imagining.
ok, will check it out
The rest of the experiment please. Where we add a detector and we see only two stripes! Can you make a video of that ? thanks
+Youssef Mejri I can't even imagine a way to detect a single photon without disturbing / destroying it. I've heard this claim many times before that if you observe the single photons going through one slit or another that it again acts like a particle... I've also heard of people turning off the detectors and it continues on like a wave once again.... and further crazyness of keeping the data collection on but then later destroying the data, and the photons acting like waves still (crazy).
Buy really, how can one observe a photon without actually converting it into a current? It isn't exactly like you can sense it's presence or something - can you?
+George Viaud The detector is literally sensing where the photon is hitting. It doesn't matter whether the photon is destroyed or not, because what matters is what it did before that. It's like shooting bullets at a target, it doesn't matter if the bullet is mangled or destroyed upon impact, we still know where he hit the target.
phiefer3 I think you're talking about sensors on the target plane and not at the slits? If so my question still stands, how can one observe a photon without disturbing it (or destroying it for that matter). Thank you for your interest in my question.
"how can one observe a photon without disturbing it (or destroying it for that matter)."
As I said, you don't have to. It doesn't matter if it's destroyed or disturbed when it hits the target plane, that happens regardless. When the experiment is done with a constant beam that's still happening, and we're still "observing" the results in the same way, by the pattern on the target plane. The only point to this variation of the experiment is to see the results of a single photon at a time, ie a single photon hits the target plate, record where it hit, another photon hits, record where that one hit, etc. The purpose of the detector is simply to be sure that only one photon hit at a time (to ensure that there wasn't another photon for it to interfere with), as well as to record where it hit because we can't see it with our own eyes.
Other than that, it's no different than the constant stream experiment, that could be done with the detector as well, we'd just get really high numbers for the number of photons hitting it and we'd generate a graph in addition to the visible results.
The distance between 2 bright spots Δx = Lλ/d, where L is the distance to the projector, λ is the wavelength of the incoming light, d is the distance between both slits. For the wavefunction of the photon ψ(x), Lλ/d is half the wavelength, so the wavenumber k = πd/Lλ. The form of ψ(x) = cos(πd*x/Lλ), where x=0 is at the position of the middle band
Not at all an expert, but from what I have learnt so far from YT suggests to me that light is more of a wave; a quantised wave i.e. what we call a 'photon' is only really a short pulse of a wave in the EM field. Imagine holding an infinite rope and just sending a few cycles through it, which will together form one pulse. That pulse will exhibit the characteristics of a wave, because, well, it IS a wave, but it will also behave like a particle, since it's not infinite.
That's a really good analogy (is that the right word?). In fact, this may be the best explanation - or thought experiment? i have ever heard.
A particle when is stopped, a wave when is moving through a field of force.
:-)
Can photons stop though?
@@ゾカリクゾ Yes, you are right, Photons can not be stpped. Actually, what I tried to say that it can be "trapped" by a field of force oscilating in a higher frequency then it.
But this is what I understood about fields of particles.
:-)
@@ゾカリクゾ I think photons are particles interact with a kind of barrier which avoids to travel in a speed limited. What do you think about quantum vacuum interaction?
:-)
my brain explodes everytime I watch these videos
still looking through youtube for a real life filmed (no funny animation) experiment showing the breakdown of the interference pattern due to the introduction of observation and slit passage identification. seems I can't find that...
you are not alone there.. :(
That's because it's not something that can be filmed. This paper describes and includes data from a real world delayed choice quantum eraser experiment:
arxiv.org/abs/quant-ph/9903047v1
Don't let the math equations scare you, just ignore them for now as they are not required for understanding how the experiment is conducted. The results on page 4 are as close as you will probably get to "seeing" the change.
Me three.
here is a real experiment with a quantum eraser: arxiv.org/abs/quant-ph/9903047v1
that'd be because it has nothing to do with literal observation or slit passage identification
You make my time more valuable
I think it’s awesome with experiments that have to do with discoveries about the atoms or with the double slit experiment, we are making “discoveries” about the photon or atom, but what we really are doing is making assumptions on what the thing is SOLELY based on how it interacts with other things. I think it’s awesome because we see how the model of the atom has changed over time based on what observations were made concerning how things interacted with eachother, but never being able to just use a microscope or have some sort of super precise amazing measuring device that doesn’t interfere with the system at all.
What if the light photons are actually particles, but they are "riding" on a "background wave" that is everywhere at all times? We think we are seeing light as a wave when the particles are not being fired one-by-one, but when we do fire them one-by-one they still behave like a wave... so maybe it's not that the particles are behaving like a wave, maybe the "background wave" is what allows the particles to move in the first place. The double slits break up the "background wave" that the particles are "riding" on, causing the interference pattern over time...
Niclas Kupper
The Michelson-Morley experiment posited the Aether to be a medium a photon would have to travel “through”, where as what the OP is wondering is does the photon travel “on” a wave.
Taking this thought a little further, in the instant a photon (can be electron as well) is generated, a correlated wave forms instantly for that photon to travel on. A better way to explain this is the wave becomes the instant roadmap of all possible paths (meaning the entire wave pattern in all of space-time is established instantly) the photon can travel and if direction is accounted for, the particle would have a specific predetermined path at any point on the one wave boundary (almost like how a surfer rides a wave). If the wave itself is instant across all possible paths in space-time it may explain quantum entanglement as the particles full path is entirely predetermined by the wave therefore measuring one of the entangled particles, regardless of distance between particles, would instantly reveal the measurement of the other particle.
Or taking away the instant characteristic (and dismissing QE all together) the wave may very well travel at the same speed as the particle (or other way around) just as the same example of a surfer riding a wave and instead of many waves existing in a field, the wave may be just one wave cycle emanating from the source pushing the particle just like a surfer riding one wave and no other wave existing except for other surfers.
There has to be something going on where the particle is being informed by a wave as to its destination. It makes no practical sense to take the easy/lazy way of accepting a particle is also a wave just because no other answers have been put forward. It seems quite obvious to me the particle is separate to a wave and only when dealing with direction does the particle then behave as a wave and as the photon generator is in a fixed position, the wave is obviously fixed from that position as well so the particle is forced in a regular pattern.
Interested to hear what you think.
One thing I have thought is the photon may be the physical stopping/collapsing point of the wave’s energy in collision with something else following a kind of uncertainty principle of its own.
thats basically pilot wave theory
Ronin
Is there a reason Many Worlds is favoured above Pilot Wave?
@@MilitantPeaceist not qualified to answer, but I know tradition and precedence plays a huge role in the human psyche.
@@MilitantPeaceist th-cam.com/video/RlXdsyctD50/w-d-xo.html
I've heard that if you set a detector to observe which of the two slits the photon goes through the pattern you see is what you would expect from a particle. Do you know if this is true? Because that's what I thought was the most amazing result of this experiment, but it would seem unreasonable to believe that if it's not actually true.
***** So basically it sounds to me that you are saying that it doesn't matter if you observe the passing of photons at the double slit, or between the double slit and the detector, because in either case the photons will behave as particles. The easiest explanation being that photons travel back in time in order to determine how they will behave. Is that what you are saying?
That's crazy. It's a wonder to me why this isn't talked about more. It needs to be taught in schools.
what ? no... it doesn't need to travel back in time to know where to hit, its just mathematics. the wave can be seen as the probability of places where the photon will hit more and less often. as you could see in the video, you only see the pattern when you add up the results, but where they hit is pretty much random, its just that there is places where the probability to impact are higher.
I see this after I finish the quantum physics class, of course that's when I find out this exists.
Your physics explanation is beautiful like u sir
I think this is not because of waves, but photones are reflected from the thick sides of slites like biliard...
By God, finally someone who got it! Yes, REFLECTION! 👍👍👍
3:01 does that graph mean that one single photons were detected in different locations on the director simultaneously? Or single photons ended up in different locations on the director during the second?
I think single photons ended up in different locations as per Heisenberg's uncertainty principle because, if one photon could end up in multiple places, I think experimenters would have noticed by now.
Who is from RAJVANT SIR recomend.
😂
Yes 😁
@@nikhil9s yesss
Yes😂
"tons" of photons??
Thanks for helping me understand quantum fysics
This really deserves more views. I blame the title.
I only wish my Science teacher had looked like this ;-)
He's very Mosby-ish lol
Inappropriate
If I had you as my teacher , I would have been a topper
Keep doing this stuff and you'll prove the universe wrong and make in implode...
The best part is the universe should have imploded in the 1930s. ;)
Conclusion: light is an EM radiation that has the properties of wave and particle.
I believe in science for all the answers to our questions.
So, is a photon a wave, particle or something else?
@@R4J4N No one knows yet, it is a conundrum in Quantum universe. Because of this experiment, let's just accept that light is both particle and wave and neither.
@@R4J4N Neither. It's a quantized excitation of the electromagnetic field.
Option 1, is all things appear to be spinning and rotating: Galaxies, solar systems, suns, planets, electrons: it is reasonable to believe that electrons and photons have a spin. So if you shoot a spinning object at a point the spinning object will miss that point (simple baseball spin). If the spin is the only variable and has only certain frequencies they would end in a pattern.
Option 2, all objects until we can no longer keep measuring smaller items have been made of smaller items, so it is reasonable to believe that even the smallest items we have been able to measure have made up larger things (excluding quarks, leptons, bosons, gluons, photons). One could reasonably believe that even these subatomic particles could be made up of multiple smaller particles that we currently are not able to measure and inside of the subatomic particles the smaller particles could have a spin and hence affect the pattern that may be produced when shot towards a single point.
Just a thought
It actually makes sense, if an electron can only have a definite location when observed, this effect would act on the photon as well, making sure it isn't in its wave state and preventing it from acting like a wave at all. Effectively making it a particle when observed, and a wave when not.
if you make ripples in water, you have a wave, but water is still clearly made from particles, you would say that the wave is standing in a medium of water, similarly, couldn't one say that light is a wave standing in a medium of photons?
I am not a physicist but in the case of water, the wave passes through the medium yet with light the photons are the wave itself passing through empty space. Light is the wave itself, the movement and not the medium. The photon is like a single wavy thing that waves around idk but it is not the same.
it really seems to me as if the wave is made of water, if you would do the same to empty space as you would do to water to create waves, then no wave is formed, because the wave is made out of the water, if it would only pass trough water, then we should be able to create the same effect without any matter to move the wave trough and the wave itself should still exist in empty space
But when the wave has passed, the water is still there whilst when the photons have moved through a region of space, that region is empty again.
but what about where they get a stream of water from a hose to stand in a wave, that water passes on as well...
+Nienke Fleur Luchtmeijer but the water does not move per se through a wave. Gravity ignored, if you move your hose up and down, the final result might look like a wave but actually every molecule moves in a straight line and the wave exist as an illusion because of the hose moving up and down. A photon, unlike a watermolecule is never at rest and always moves absolutely at the speed of light and it moves as a wave. The particle itself waves up and down so to speak whilst the beam of light does not. Water has to be shaken yet every molecule still folows a straight path and doesn't wave itself whilst photons don't move in a straight line and the beam of light doesn't have to be shaken to produce a wave since the wave of light is a different kind of wave than a waterwave.
What do you mean when you say light is waves? Waves of what?
Next year I will learn about waves in school but from what I have heard I won't really learn the real nature of them, just a bunch of math.
I know that sound waves are just molecules going back and forth pushing each other
but what about about light waves?
sometimes the best questions are asked by the un-indoctrin... uh I mean un-educated people. Waves of what exactly, no one knows... ether.. Its simply a way of describing the phenomenon.
Each quantum-mechanical particle is a wave. A particle is not like a spherical ball as one would imagine it to be. A particle IS a wave. I don't understand why people make this so complicated. So the question of particle OR wave does not even make sense! A particle is a wave. Thus different particles can interfere with each other, and a single particle can interfere with itself -- because they all are waves.
subh1 you are right, i couldnt agree more, there's no particles, just waves. that's why wavefunction works. there's no any particle functions in QM. it is funny that physicist dont see this, and still call wave-particle duality to make simple things complicate and confuse everyone.
Charles Yu I think the photon must have a field which pass through both slits creating patterns which pulls the photon side to side. The field is undetectable just because is part of the structure of space and time, unless we hit the speed of light so, particle is a particle and wave is a wave, it is impossible one particle pass through both slits.
Charles Yu I think the confusion stems mostly from the phenomenon of wave function collapse, which is still less understood. But then, even after the collapse of the function has happened into one of the position eigenstates, it's still remains a wave (may be a highly localized one like a dirac-delta function, but it's still a wave).
Also, in the non-relativistic QM one can still talk about a wave function for each "particle". But in light of QFT, there is actually a single wave function that encompasses all particles! So the "wave-particle duality" is really a vestige from the past (early 1900's) when QFT was not developed and quantum phenomena were less understood.
If you model the photon in terms of E-M fields, then something important becomes apparent. Let the E-field be aligned with the slit and the M-field perpendicular to the slit. The M-field experiences the magnetic permeability of the material, which is asymmetric due to the presence of the adjacent slit.
Now, Maxwell's Equations come into play. One has to reckon the effect of the lopsided discontinuity in the magnetic permeability. The effect is to deflect the photon to the side.
Note that a comparable calculation could be done for a beam of electrons, where the electrons are modeled in terms of Gauss's Law (spherically radial E-fields) and Ampere's Law (circularly symmetrical B-field disks). Even if the center of the Guassian sphere passes through one slit, the B-field will encounter an asymmetry due to the adjacent slit. Again, Maxwell's Equations would come into play, with Faraday's Law producing a lateral force to deflect the electron to one side.
Except that the slits are far far far larger than the wavelength of the light. They won't significantly interact with the wave.
Light is the summation of probability waves (Richard Feynman - Quantum Electrodynamics). The single photon doesn't pass through both slight, the photon's probability wave does, because the probability wave takes all possible paths. If no attempt is made to resolve the probability wave into a single path by attempting to determine which slit the photon went through, then the probability waves will interfere and the resulting resolved photons with create an interference pattern.
Looking over my notes, I came up with this new picture of a photon particle wave. Bit difficult to describe in words, but it is based on photons that can create positron electron pairs.
Photons are a series of particles like stepping stones. At each stop the photon shoots out a positron crest in one direction, and an electron trough in the other.
This LOOKS like a single complete wavelength.
But it really is a photon turning into an electron positron pair, each springing out of the photon in the opposite direction of the other.
So each wavelength is, photon in the node of the wave position, with a negative electron trough on one side and a positive positron crest on the other.
Further the node between two wavelengths may be where an electron trough meets a positron crest = annihilation.
This process would all be as quick as a quantum jump.
I don't think that we know what a photon is yet .
If it was like a segment of radio wave then it will spread out in the x , and y dimensions as it travels though z
A photon is to electrical magnetic waves --- as --- a smoke ring is to pressure waves
It has something to do with standing waves and a resident with space and time .
You realise radio waves ARE photons, right?
re: "What happens when single photons of light "
No. It is _not_ possible to create a single so-called "photon" ... you cannot even much less DEFINE the size of a photon let alone create a lone, sole 'photon' ...
Better video showing wave interference using microwaves and radio waves -
th-cam.com/video/tY3_78ONkmI/w-d-xo.html
At 17 : 53 is the microwwave exp.
Waves are not a thing, they are a pattern of movement. It took me awhile to understand this because of the noun like way we refer to them.
+Glass Menagerie they are a noun though. Nouns, and even "things", do not have to be physical objects. An idea is a "thing", a word is a "thing", a question is a "thing", a name is a "thing" and even movement is a "thing". So yes, even waves are "things", even if they do not physically exist.
Thank you for your amazing content! You're helping me so much!!!
Finally i understand now how this experiment was performed.
Photons are... the Border of Wave and Particle
Please tell me someone gets this reference
I still dont get how is it possible to know that you are creating what you call "a single photon". Wasnt light a wave in the first place? How can you make a particle like thing if light have a wave nature in the first place????
It is a wave and particle at the same time
How does it count things so, so small?
+MVasdf Oh SNAP!
I'm not familiar with the specific equipment used in this video, but here is one possible method. Each photon has a discrete value of energy. If we know the frequency of the light emitted by the laser (which we do), we know how much energy each photon has (E=hf). Therefore if you aim the light at a detector and measure those discrete changes in energy as each photon hits, you know that a single photon is hitting.
Photomultipliers use a sort of "domino effect" of electrons to count each photon. When a photon hits the detector, it excites an electron or two on the detector. The photomultiplier uses a high voltage to accelerate the excited electrons to a high velocity, allowing them to excite even more electrons This process is continued until there is a high enough number of moving electrons (electric current) to be detected. That's why they're called "multipliers"; because they physically multiply the effect of each photon until it's enough to be detected.
The gnome inside is super tiny
your eye is able to turn groups of 3 photons into an electrical signal
If photons are interfering with each other after they go through the double slits, why doesn't the interference cause the photons to experience a "collapse of the wave function"? If the photons are interacting with each other, they should show up at the detector as random points with no banded wave pattern since the wave pattern has been wiped out by interference. .
The interaction is not the observation.
@@karlkarlsson9126 ~ The interaction should affect the observation.
@@FrankCoffman Interaction between particles is an entanglement, it's not yet an observation. When one wave interferes with itself after going through two slits, it's still just a wave for one particle, it doesn't interfere with another particle.
@@karlkarlsson9126~ "...it doesn't interfere with another particle." It's assumed that interference between photons does occur after they pass through the double slits. That's the accepted explanation for the double slit experiment when a banded pattern of photons appears on the barrier. The bands are supposed to indicate wave interference. But why doesn't interference wipe out the waves, causing the photon waves to collapse into random point particles?
Also, how can photos interfere with each other -- "Since light itself does not have electric charge, one photon cannot directly interact with another photon. Instead, they just pass right through each other without being affected." So how can photons interfere with each other if they don't interact?
@@FrankCoffman It's the wave that interferes with itself, not the photons with each-other or with itself. It's not a photon yet until observed. So you have the answer is in your own question, there is no collapse because there is no particles interacting with each-other.
In Quantum Mechanics there is no particles, only waves of probability using the Schrödinger's equation, so a particle is described by a wave function, and when two particles interact it's two waves interacting, they will share the same wave-function (entanglement).
For waves to become particles and behave as particles they need to collapse, being observed. The end results in the double slit experiment showing the wave-interference is particles showing that they traveled as a wave but hit the screen and collapsed as particles.
ive heard in a lecture by Richard Feynman that light is defiantly a particle. the duality conundrum comes from us trying to explain the behavior in familiar terms but there is no doubt that light is a particle in every sense of the word.
when we try to predict what happens we find that the same mathematics that describe waves gives a probability of where the particle will go. we cant say with certainty that the particle will travel a defined path, but we can say with a great deal of accuracy that given a large enough sample you will see signs of interference showing up.
he has provided incomplete information about devices used in this experiments.
He says about Photo-multiplier which detect the photon and Frequency counter which counts photons per second.
how the position of photon found and plotted graph?. which device is used here?
Vijayan T good question. i saw your Quantum Eraser video. but do you know typically how to record the photon location on the screen? although we are sure photons definitely just cohere with itself, but it will still be useful to know how the device did it.
He's putting the photomultiplier in one position, measuring for a while, then shifting the photomultiplier to the next position. This way he gets a photon count for each position, but it's important he measure the same way at each position.
Photon = Compression wave. There is no photon particle. Check video "LIGHT: Deeper Secrets of Light & Nature's Field Geometry".
“Dim light “is not the same as a “single photon” what you just did with your graph over time is the same as a long exposure in photography. Prove that a dim /faint light source turns it into a object (particle)
Here is a scary thought -- what if the single photon interference pattern is in fact a superposition of all possible outcomes and it effectivelt interferes with istelf through its own superposition???
My left ear enjoyed hearing your voice
wavicle
I also love this term. I feel it should be officially adopted instead of wave-particle and particle-wave. It's too convenient!
Derek, Have you thought about patenting this word ? :-)
Einstein wouldn't agree with the term
A single photon can never show interference patterns
you totally missed the point of the video then
There is no such thing as single photon. Boy, I wish to make "anti-veritasium" (latin: veritaserum) TH-cam channel. Or "Mendacium" channel. "The channel of lie". :D
so it's not possible to produce individual photons?
well like he says a photon isn't a particle. why than does he think he can produce a single discreet "one" of them? there is a contradiction there.. the duality conscious mind doesn't see reality as one whole.. instead it believes finite things to exist.
Because you can create single photons. You can divide light down into its smallest element, but no farther. If you try to send less than one photon, you send nothing. You can measure which slit the single photon is going through. And if you do so, they stop acting like waves, and start acting like particles. You can count the single photons in a detector.
This was proved by Einsteins Photo electric current that photons comes in lumps only. not half lump or 1.5 lumps.
Awesome experinment,blowed my mind
I found you from my Astonomy class, now I just watch you for fun and education. Great videos, very fascinating!