It's great how he presents the historical arguments about quantum mechanics and he gets so emphatic about an important point. Excellent!

what an amazing and effortless approach to the concept. loved it!

I realized that the textbook I've been reading sounded familiar and it was written by THIS professor! Incredible!

"That's how He fall you in love with Physics.." Excellent lecture as alwz!!

Brilliant! Loved how he made it so simple to understand the superposition of states

Absolutely brilliant explanation. Wondering superposition being so easy a concept, lies the fact beneath it is not the case for QM. Must thank you Prof.

Peru is proud to have produced such a good teacher

Fascinating video thanks Barton Zwiebach!

The reason quantum mechanics is so puzzling is that the experimental results themselves are intrinsically puzzling. Quantization is counter-intuitive. Turning everything into waves of probability works as a mathematical model of the physical phenomena, but waves of probability don't really make sense to us. We have perfectly good mathematical models that predict results to stunning accuracy, but we just can't fully accept what the math is telling us because the way it works seems fundamentally un-physical to our limited minds.

Brilliant lecture!

Great lecture that inspired and motivate teachers and students. Thanks MIT

It depends. If you entangle the particles and get them through a detector at different angles, you'll observe that only specific angles will give you "right" proportions for detection (fractions) when you measure spin.

really clear explanation!

Very well explained!

Beautifully done ✔️

What a lecture sir. Just awesome.

Excellent lecture Sir Thanks 🙏🙏🙏🙏🙏🙏🙏

Really good course!

His Inca name is Amaru Qapac, which means “Chief Dragon”, and is an Alumni of the Peruvian National University of Engineering (UNI). He is our champion!

Great camerawork

Thank you sir Its good stuff

The problem here is the "existence" of the photon between the source and the detector. The source can infer the photons existence, the detector the transform of the photon. The path/paths are assumed.

Hey MIT OCW and Prof. Barton Zweibach, your lectures are incredible. BTW I do not know why I laughed so hard at some photons can go both and down.

At 14:30 - wow. Each photon must interfere with itself... which makes sense given the set-up and the speed of light (different quanta could not interfere with each other as they arrive at different times). But this says something very deep about the underlying construction of the universe, and things like three polarising filters allowing light through, where two polarising filters do not, seems to be the same thing. But this implies directly that the holographic principle is correct - that the universe of our experience is actually a secondary phenomenon riding on the back of something more fundamental, and that Schrodinger's equation just catches that main idea.

I was lost after the professor said superposition.

These lectures really are wonderful and I can't help but think about harmonics and waves when the Professor is erasing things. No, seriously. The audio capture and reproduction technologies nowadays are really impressive, you can really feel it! Squeaksqueaksqueaksqueak! 😬 It must be that dreaded 7th harmonic (maybe)

About superposition : as I understood, a photon can be either in A or B state because thats the only way to explain results of experiments. How reliable these experiments were (blasphemy!), but curious to know what was done to validate experiments and design them. Also, are there alternate explanations.

Excellent lecture ! But I m not able to understand if a photon is indivisible how it can go in two directional simultaneously as sir said just nearly 6:30

how Mach Zehnder Interferometer gate represent universal gate library? plz help me

God bless you for this course! Thanks from Poland!

thanks a lot

Hi! How can a photon interfere with itself? Isn't also the energy conservation law being violated? Because we have something like: photon -> 0 (for destructive) and photon -> 2*photon (for constructive). In these equations photons are monochromatic.

how phase shift happens in a beam splitter which is an half silvered mirror

6:51- mind blowing 😱 but so fascinating 😇

After watching this lecture, I got 2 questions in my mind. 1. Why we use States as a vector in Dirac notation? 2. How would Two photons interact with each other, because Photons are the interaction particle for electromagnetic waves, so how would they interact with themselves?

fathi medos fes said thank you so much

5:28 The moment when he says each photon is interfering with itself is like a revelation of a big plot twist in a movie.

Inspiring....

Is quantum mechanics useful if we wanna go in aerospace propulsion research???? Please someone tell....I wanna make my career in it and I don't know whether to study it or not...

Its very hard to imagine a single photon in two different beams but they exist

As someone who only did one year of college. This makes me want to go back.

Svp puis je avoir cette vidéo en version française ?

Does this mean that if a quantum computer is to work many repeated ‘calculations’ must be done? If so, how is this any different to an analogue computer?

Quick question: how does the double slit experiment work with photons if supposedly they don't interact with one another? Just trying to understand the nature of the photon first before complicating it with mirrors and all the rest...

Quantum mechanics is just insane lol. I’m so happy I live in a time that has found this nonsensical state of nature.

It's like on the subatomic level reality is being constantly created. Every photon, electron,etc. is potential until it settles into definable state.

I don't see what prevents superposition in QM to be explained with classical superposition of waves. (and by the way, cube beamsplitters are positionned so that the incoming beam is 90 deg to the cube surface)

Wait, how would you differentiate superposition of a particle from the same particle being in two different places with such a tiny time difference that it would be undetectable to the human eye (or even available machinery)?

Can photons be sent one by one? If it were that way, the size of a photon could be determined by moving the array of mirrors and when no signal is found it is because the photon has not yet arrived.

It cannot be that each photon interacts with itself only. If that were the case, then slight differences in length of the two paths would prevent the photon to coincide in space with itself and no interference of any kind would be observed.

How many times can the interferometer split the beams of light? Are there limits on superposition?

para cuanto una clase en español prof

I think there is some information being lost in his description of what is interesting about the interferometer. When he says that it can be arranged such that one detector or the other sees all of the intensity it is easy to imagine a scenario where each beam splitter passes either everything or nothing. All of the outcomes to that setup (where each splitter passes all or nothing) are that all of the intensity lands on one detector. I think that what is unique to quantum mechanics is that you can separate the beams with both beam splitter and still get all of the light intensity on one detector or the other.

Anyone know what year the students are that are taking this course?

2:01 Explain_ It may be possible that light entering in second beam splitter from both ways goes in different directions so will not interfere.

Words don't make sense. Senses.., interpret the interactive shaped occurrence of probability, for which we have (inadequate-incomplete) words, but this a good Methodology of illustration/teaching.

So the measurement itself is NOT linear? measuring |A> or |B> is different of measuring alpha*|A> + beta*|B>

@5:04 it would not break conservation of energy

Why he didnt use the double slit experiment to show the nature of superposition ? Does the Mach Zehnder interferometer shows it more explicitly. I didnt understand that.

Is it true to say that |A> and |B> orthogonal states?

Superposition: when the sound of that eraser is EVERYWHERE

I can understand how this can happen geometrically

They have something against white boards?

How much is the right answer with an experimental demonstration worth?

Since you brought up linearity in the beginning and claimed that the SE is linear. These wave functions are solutions to the equation, then how come you can have such superposition

Love From Kashmir.

Do these two probabilities always sum to 1 or 0 !

It doesn't seem plausible to carry out the experiment with one single photon. I don't think there is difference between the quantum and EM superposition.

this is crazy

How exactly do you "send" only one photon?

👍👍👍👍👍👍👍👍

5:24 = Dirac, but is it the only one explanation?

I am here.

Guys top universities still use Blackboard and why?

💌

if a photon is travelling in both beams, how does this not violate conservation of energy?

ABC and q

TONOMURA-experiment: kzfaq.info/get/bejne/oNx_Y7NmkrmxqJ8.html

8:51

0:54. "Zehnder"

8:51 he wrote Ass

6:20 Wait, if a photon is the smallest energy for light, and you're telling me you can split it, then it's not possible that a photon is the smallest Quantum of light, the half Photon must be. What are the energies of the to split halves? They can't both be one quanta of energy. Sounds to me like some physicists are not doing their proper due diligence.

Sir 1.how energy is conserved when a photon superimposes with itself? 2. Why in QM only a or b and why not a+b ..because QM is probabilistic in nature? Please reply as soon as possible.

ugur was here

Just because we see an interference pattern, doesn’t mean that photon is going both ways. That may be one way of explain it, but it’s more of a metaphor than rigorously proven fact, am I wrong?

you did a good job A lot of thanks from HINDUSTAN(INDIA)

4:35 is the nail in the coffin for classical wave theory. "A bunch of energy canceling each out into nothing" is impossible by laws of conservation of energy that classical theory champions. Just shows how broken classical theory was.

0:18 electric fields in 7 seconds

It's the only possibility...:Fluid theory (Reproduction/Feed/Reasoning) decanted selfover hexagon...

The struggle of professors and teachers;They have to repeat the same thing over and over again for at least 30 years,and that comes with many challenges and risk of losing their jobs because their livelihood depends on it.Basically,every jobs are like this,you must repeat the same texts again and again,and they thought this is a career when its only a job,if it were a career they would go on progressing but its only a job so it gets boring as every job is.But quantum physics is different.

Arguments sure look deeply flawed to me. If a photon has a frequency (E=hf) and yet has a limited spatial extent in order to be particle like then the frequency becomes undefined! Frequency is events per time interval. To be a ‘particle’ the photon would be way to short to allow vibrations of its electric field so that it could be said to HAVE a frequency.

Great lecture, but unfortunately a lousy student. I think I'm condemned to only understand physics as it was till about the time of Rutherford and Maxwell.

I think any dynamics at the microscopic level should be confusing

PUT THAT COOKIE DOWN!

OMG, I know it's like the least important thing here, but the way he writes dots and dashes and how he (like in 1:02) can even mistake a dot and a dash is just so funny (good funny - don't you judge me, I so love these kind of things!)

This is not about the nature of superposition, at all. It's about the nature of maths on measurements of superposition. No description of what superposition physically is. All the way from the school definition of momentum as "product of mass × velocity", as if that piece of abstract maths is what it physically is, this is always the con in pure physics. It's never actually a physical description of anything's physical nature.

中国人在看 好有吗？

Idheto pothandhi rooooo

When my mom walked in I changed the screen to porn, cuz it was easier to explain

Every reflection in some way is refraction! Everything passes through airborne particulates, frequencies, etc. therefore altered from its origination, no true rendering. The returned image, whether it be the eye or heat, light, etc. is casted, meaning the defused in this case, using your splitter, the primary chamber creates chaos and loses the fullness of the beam, this is refraction if you will, this furor is only partially retrieved and sent to the secondary! The primary continues to collect what was lost in the initial reflection "actually refraction*... This increases the strength of the primary output! Focusing to a desired point with disproportionate energy offsets your calculations, therefore your rendering is inconclusive. You yourself said you did not fully understand in your video! The manipulation of digits to statistics are no more than self proclaimed, not unlike the perimeters of an aquarium. Is this not a form of matrix?! Human "thrives" due to the ability to reverse engineer what is observed. I did not say "flourish"... The engineering is no more than claiming the understanding. One cannot re-create what is not understood this is why your practices simply unsustainable. You will never understand creation nor creator. Just because human can recreate life, you have overlooked the variables and your outcome is tribulation... We are electromagnetic ephemeral Tellurians, nothing more than synthesis to Genesis. The manipulation to fit the rendering is a farce. This is a matrix within a matrix within a matrix so on and so forth. It is time to step back, cogitate, ruminate on your direction. For your direction is our direction and forced fed! Many of us live with bird in the hand, proof and direction too... You take us away from reality in a already distorted world. What I have stated here is provable by every human being that is not disinclined, but your offer is limited to your thesis, your calculated outcome, "calculated" in every sense of the word is misconception due to leaving out the variables. This is why more than not, a creation of something is more harmful than anticipated. For example try to contain every heat wave that comes from the surface, roads, rocks, etc. you cannot contain all, meaning you have not accounted for all of the variables and the outcome, the rendering is false!!! Love to ALL