I have to disagree. It has some useful ideas but there is a lot missing. It is just a quick lead in to subsequent material. He is getting people used to working with operators.
Lenny, you are the kind of wonderful genius that makes such a difficult topic so accessible. Your natural warmth makes one absolutely ENJOY your lectures. Can't do better than that! There ought to be a "Professor Lenny Susskind" commemorative stamp. One of my very favorite American heroes!
I cant believe this material is so freely available and good. Just like being back on my course 25years ago but this time I can pause the vid to try and get my head round it all (again!). Students today dont know how good they got it :-)
neil u because it’s the anti electron which by the conservation of momentum and lepton number is required to be opposite in charge ...we also know that when a positron and electron interact they annihilate one another and produce a photon of light which only happens with particles of equal but opposite charge
neil u spin is also involved ...fermions have half integer spin ...by the Pauli exclusion principle the two fermions cannot exist in the same quantum state or in other words have the same quantum numbers simultaneously ...field theory uses second quantization to handle this through creation annihilation operators and slater determinants to ensure anti symmetry
What I love about Prof. Susskind is that he not only shows us the Mathematics, but also tells us the meaning of the Mathematics. That kind of understanding is difficult to get from texts.
I can't believe we have the likes of Leonard Susskind's to teach us so freely, i think it is amazing that these Goliath's of science aren't much more appreciated.
It took me until minute 15 to decide "ok. This is going to be really interesting". Thank you Susskind & Stanford for putting these on youtube. I hope I can grok it.
Rehearsing QM formalism; Symmetry 1:02:45; Symmetry operator is Unitary 1:09:00; Symmetries commute with Time evolution and hence with Hamiltonian 1:16:30; Discrete and Continuous symmetries 1:23:30; Generating function is Hermitian and commute with Hamiltonian 1:25:30; Translation symmetry example to derive momentum operator 1:29:00
Quantum physics is something abstract at least in our daily routine life that always needs to be imagined. Here Prof. Leonard Susskind visualizes so many simple known mechanical facts in quantum, therefore, everyone even those with a little level of physics understands them very strongly.
Don't forget Computing and communication. Computing is everywhere. To tell nothing about communication. QM is gonna give us Quantum computer and Quantum communication.
Awesome vid!! Thank you to this professor.. he does an EXCELLENT job of teaching new concepts!! I’m a hobbyist, and enjoy watching these in my spare time to learn more about the world and how it works. Very informative and much appreciated.☺️👍🏾
Wow. I just graduated 5th grade and wanted to expand my knowledge on quantum mechanics to prepare for middle school. I think that this video was a great lesson and I look forward to watching the rest of this series.
1) Review 00:13 2) Unitary time evolution and generator of time evolution 29:38 3) Translational symmetry and its generator 1:02:36 Next: Generator of Rotation and its generator.
Lenny is a down-to-earth version of Dick Feynman, who could be too brilliant for everyone else in the room. He's an excellent teacher who never resorts to hand waving, but follows through with clarity on every detail. If you are one of his students, and are willing to do the work, I would expect that he would make sure that you succeed.
I am 13 and I love this stuff. Don't say it is boring, because it is not. Quantum mechanics opens up all kinds of possibilities. Quantum computing for example is just one of the many uses of quantum mechanics. The amount of possibilities is almost as mind bogeling as the psysics itself.
You are 13 already? Dang, Im only 3 years old and yes all those equations are so interesting. I love quantum mechanics. I already have 5 published papers in quantum physics. Excited to see what the future holds
Great revision of the QM1 course. @1:19:33 For the first time QM matches common sense: Q: "What requires V to be unitary?" A: "It is an assumption that symmetries of nature take orthogonal states to orthogonal states... that seems plausible..."
At a minimum, you should watch his Classical Mechanics lectures followed by his Theoretical Minimum (quantum mechanics) lectures before this one to get the most out of it. You should be familiar with the product rule and chain rule of differentiation, integration by parts, basic matrix algebra like dot products and determinants. Familiarity with Fourier series and transforms helps a lot also.
oh my lord, I cant watch this right now, since My final exam in Account is within a month, But this is so tempting. I have been doing lots of self study, never in my dreams expected this is to be so freely available. . I just hope this doesnt get removed any time soon.
I didn't believe these complex concepts can be explained so simply..... I was stranded in the deep woods of QM but Susskind's lectures are a source of light......... here I practically see einstein's words 'only he who understands can make others understand' ... btw these are the inverse of Einstein's actual words...
Lmao, I had a kid like this in middle school, he would use fancy words that he didn't know the meaning of after watching a simple physics video and when asked what they mean he would just say "oh you wouldn't understand".
It takes some time to unlearn concepts that you grew up with and are considered 'common sense'. If you watch the "MATH YOU NEED FOR QUANTUM MECHANICS" lectures first, at least the mathematical terminlogy becomes much clearer.
Why can we just change the signs at 47:32? I get that we want the G^hermitian = -G to become H^hermitian = H, but wouldn't that affect the U(t)psi? thank you!
We add the imaginary number i because by definition U^dagger means to transpose the matrix and take the complex conjugate (also known as taking the Adjoint of the matrix). So if H is real, we can;t just change the sign of H by taking U^dagger; that is, if U = 1+eH and H is real, then U^dagger = 1 + eH. But if we add an "i" in front of H then when we take the complex conjugate we actually get the sign change we wanted, that is, if U = 1 + ieH and H is real then U^dagger = 1 - ieH. Of course, the Hamiltonian is complex because H = -ihp^2/2m + V(x) = -ih/2m (d^2/dx^2 ) + V(x) but -H does not equal the complex conjugate H* (to see this multiply H by -1, then actually take the complex conjugate H*. You'll see that -H does not equal H*).
Hmm, Lets do poors man calculation. Videos are generally 2 hours long and assuming he stands for 1/4th the time to explain stuff and other 3/4th the time walking and writing on the board. So total time he walks is more like 1 hrs 30 min. Now assuming an average walk speed to be 1m/s. Calculating its in hour gives us 3.6km/hr. Now hence putting it in vt=distance we get, 1.5hrs*3.6km/hr=5.6kilometers each session. Hail lord fermi.
Can someone explain why these lectures (and other videos) are posted many times on RUclips - by Stanford but also by lots of other people - when you view them they seem to be exactly the same ones. Why do lots of other people publish the same stuff? - what's the point?
Most of these students asking dumb questions should revise prior to doing Advanced QM. Both Heisenberg matrices and Schrodinger pictures are required in QM as the first describes the discrete quantifiable eigenvalues of the eigenfunction psi whereas the Schrodinger picture describes the continuous picture of a quantum picture. Schrodinger picture is always the initial state of a particle. The Heisenberg picture better describes measured states like angular momentum, spin etc ie values of observables
Very interesting! I love prof. Susskind, especially when he eats his cookies! I've been attending all his lectures, It'll take years... :-) thank You prof!
Can we not do an observational experiment of a partical of position n momentum at same time to then get both its position n momentum, why can't we observe both simultaneously dule experiment on same partical thus defeat this idea of can't know both, it's one or the other, seams can use a pc to calculate math if take calculations of partical at multiple spots then give position and it momentum...?
You can measure both at the same time. What you can't get is the same values every time you do this measurement. There will be a considerable uncertainty in the statistical distribution of these measurements.
I put on my clothes, C, and multiplied it by my morning tea, T and then added a generated number, G, which I got by subtracting the symmetry of how many seconds it took to tie my shoes, S, and I got the translation of how much traffic there will be on the way to work, as a wave function, W.
I don't think he proves that here, but the hamiltonian corresponds to the energy of the system. It appears in the time-dependent schrodinger eq which in turn comes from the assumption that the evolution of the system is governed by some operator which is to be close to H for small time spans. Its just a matter of where you create it and where it is significant. idk if this is exactly what you asked. ruclips.net/video/tRWBoossG0Y/видео.html could help too.
Orthogonal means the scalar product of the two vectors is zero. Linear independence means that no linear combination of the vectors is the zero vector.
In the part where he talks about conservation of information, why does he insist on 2 states being observably different being the same as the 2 states being orthogonal? Aren't two states that aren't multiples of each other but with non-zero inner product still observably different? What am I missing? Thanks!
He talks about it at length in his basic QM course. In short, when we perform a single measurement of an observable Q, we can only get one of its eigenvalues a, and then the state of the system collapses to its corresponding eigenvector |a>, meaning that the previous state is irreversibly lost. We say the states |a> and |b> are 'observably different' when threre exists an observable Q, such that after measuring Q we can say with certainty whether, before the measurement, the system was in state |a> or in state |b>. Due to math, this condition is equivalent to |a> and |b> being orthogonal - when they are, we can possibly craft an experiment to distinguish these two; when they are not, such an experiment cannot exist even in theory. A practical example is the spin of an electron. We can easily measure between electrons in an |↑> state and a |↓> state, but there is no possible way to reliably distinguish between electrons in an |↑> state and a |→> state, because they are not orthogonal, |→> = (|↑> + |↓>) / √2
At 1:08:40 he says that the operation might correspond to squeezing or stretching, which are not symmetries. But then a few seconds later he requires that V be unitary. Did I miss something?
He uses V in the first case to say that doing anything corresponds to multiplying on the left by an operator. Next he is talking about operators representing symmetries, and he uses V again, a particular case of the first V. It's commonly done in mathematics, called AOL "abuse of language"
in the G deduction: (1+epsilon*G)*(1+epsilonG*) = 1 becomes epsilon(G+G*) + epsilon^2 (GG*) = 0 but he says: epsilon(G+G*) = 0 Why the epsilon^2 (GG*) term vanishes? is it too small, as epsilon is a small amount of time?
Edit: His last sentence in the lecture said the symmetries that do not commute with each other have real power …. More to the story I guess. But still wonder why groups are NECESSARY.
The only bright thing in 2017 that's not something god forbid, is being able to study advanced quantum mechanics from freaking youtube. I'm now half an hour into the lecture and i did watch a thousand documentairies on this, but i still had to go trough almost 20 wikipedia pages to nearly understand half of what he's saying. I'm not stupid but i didn't realize that even considering an actual thought about this subject requires a lot of skill. Skill i've got to catch up to. But it's still realy amazing to find this kind of knowledge out here.
fabulous, here is just a basic lesson about the quantum mecanic but we can see already a implied reference to the "pullback" property (category theory) and a allusion to the "Noether" theory
Physically transformations take time. It takes time to, say, rotate and object. But mathematically we consider operations happening independent of time; that is, for a rotation of phi radians, R(phi) we only consider the change of the state with respect to the rotation; R(phi)|psi> = |psi(phi)> where |psi(phi)> represents the state |psi> rotated by phi radians. So, mathematically, we treat the rotation as happening instantaneously.
If H does not explicitly depend on time then yes. This is because U(t) is constructed as a Taylor series in H. Therefore U(t) always commutes with H. The consequence of this is that energy is conserved in time. For a H that explicitly depends on time it is more subtle and I am not educated enough to give the answer. I know this is 8 years old but I thought it may help someone else.
Ok so some people say that 13 yr olds cant get it but its really interestinf to me thos im thirteen and im understanding this fully tho sometimes a bit hard but yea i do and i just began advanced and would love tips from some quantum mechanic gods please and don't say "u cringe u probs dont know 2+2 " Keep yapping u probs dont get it urself Ive done the basics Ik what maths to learn (integral calculus etc etc) dont make fun saying ur just 13 dont do cuz i want to i reallly want to and i shall if u cringe, leave and do whatever u wanna Quantum mechanics gods please i need some tips please just for future
You also can’t just skip to quantum mechanics, you have to do classical mechanics, electrodynamics and maybe even some relativity before even starting quantum mechanics.
"Someone" should make a comments list on Henri Bergson so-called Philosophy of Time, for example what,how and why is it not simply just another interpretation of the Arrow of Time and Relativity in the Correspondence Principle format. In the ONE-Infinity unity-connection categorization of e-Pi-i logarithmic resonance Partitioning of self-defining temporal phenomena, a musical-pure-math continuity to instrumental device idea.., the image of conic-cyclonic quantization cause-effect is an aspect of ONE-INFINITY Singularity Quantum-fields Mechanism Holographic Principle. Some math-musical thinking practice.
The thing about QM that i dont like is that you never know H. And if your experiment is different than expected, you just try a different H, until it eventually explains the observations. Its like a theory with a parameter that you can guess, you may aswell just guess the results. At least thats my feeling at the present.
+phil durre All theories are like that. You have some equations, some constants, some rules, and you try different ones until theory matches. The crucial thing is that once it works, it works all the time within its range of applicability, which NEVER is just one particular instance of an experiment, which would be equivalent to "introducing the results by hand" or "guessing the results", as you described it.
Hm.. Asked a question on a previous lecture a few minutes ago. I think this answered it. Re-watching this to prepare for the coming thesis ;) I recommend everyone do the same. Brush up on your understanding of "how read this and see where it should envelope". Might be released tomorrow if tonight is right lol ^^ Check sci-journals. Thanks LS
Glossary of associated e-Pi circularity and i-condensation superposition identification of conventional-temporal phenomena. (Preliminary "sufficiency" analogue to comprehend time-timing sync-duration identification) Hermitian Operators are Real Number, Quantum Theoretical, temporal superposition real-time associations. abstract Quantum numberness vector-values. Eigenvalue Hermitian Operators-> (quality of floating frequency?) multiplies (amplitudes?). AM-FM Communication? "Orthogonal", ? approximately "the illusion of separation", (phase-locked?) between quantization identification vector-values (Singularity positioning integration?) Zero-infinity 1st law of thermodynamical orthogonality, because axial-tangential Geometry, 2nd law point-line-circle time-timing e-Pi sync-duration i-reflection phase positioning-location conic-cyclonic condensation, Eternity-now Interval Reciproction integration, in Singularity-Apature Perspective Principle.., is holistic holography, vector-values dimensionality. "Recording" or Imagery. "Wave function times its Complex Conjugate is always positive", (intuitive convention provision), because multiple, superimposed vector-values, are real-time potential possibilities and probabilities, existence sync-duration, multi-dimensional connected, (observable-> n D dominate probability vector-values), Condensates mass-energy-momentum continuous creation cause-effect connection. Operational Principle of Calculus eg Chain Rule => Dimensionality coordination. ----- Students should choose their own reiteration and reintegration patterning. "Yesterday is gone".., and never was..
@Nancy : I'm curious what drove you to listen to such lecture Nancy. I find it interesting because Qantum Physics could definitely be taugth to young students curious and open mind. But these lecture are NOT GOOD, even for avanced level. Fundamental ideas and assumptions are ill defined and not justified. Fundamental mathematical structures are treated like most physicists does, that is like tomato sellers leaving the mind in a total jam! And worse almost no crucial historical experience are reworded making the hall lectures a mountain of arbitrary words and concepts. The entire lecture stands like a trunc of a tree without any roots nor branches. It's thus a pitty that curious yought don't understand anything in such lectures, it is a sign that IT IS NOT CLEAR, even to more advanced ones that illusory believ they understand fairly more. The PHYSIC should be cristal clear even if the subject is chalenging, even to a young mind if the course was CLEAR, and finaly besides the mathematical level (if it was done properly) that woul of course chalange you (but that also can be tuned and wisely adapted to young people or amateurs, it's a question of pedagogical skill, but everything IS POSSIBLE if the will is there!) But keep in mind one very important point : that Science is like a stairway, very difficult to climb if you haven't to only climbed but insighted the previous stairs that build your Modelisation Power of World Phenomenology. And to leave you with a insightful hint Quantum Physics is a Mathematical Model (ie A PRECISE AND POWERFULL FORGED TOOL TUNED FOR EFFICIENT CATCHING OF REAL PHENOMENOLOGICAL BUTTERFLYES AS OF THE MORE SUBTILE MYSTERY OF THEIR WAY OF BIRTH, TRASFORMING, LIVING, FLYING, FLOWERING, REPRODUCING, DYING...). To leave you at least with one precise and concrete situation where Quantum Physic Mathematical Modelisation is deadly needed to catch what is happening. A simple WINDOW offers us a usefull TRANSPARENCY because SILICE atoms from witch the glass is made ( contrary to most other atoms constituing mater), do not dare to play, to talk, to hugg, to interact with the incoming light, falling from the sun and springing from surroundings. And so, THE LIGHT PASSES the Silice mater, bringing thus the light and energy coming from the sun and also the billions of rays bouncing out of all outside earth mater (trees, building etc). Thus why Silice is such an asocial atom regardless of light, why does it SNOBES it radically, is made understandable by Quantum Physic Mathematical Model. It sketches the atoms as a STAIRWAY : or you have enough energy to make at least on step and you make it or you don't. there is no "half way". Or like an apple that can't be cut in peaces. Or you have one dollar to get it or you starve. No "half way". And the final key to understand is that Silice atom make their PRICE SO HIGH that visible incoming light dare not pay even a smile exchange with the Silice atom (very rude!!!!). But ultraviolet light (more "sexy" than visible light, more "hot", more "energetic", more "rapidly shaking it's belly") succeds in seducing this selective Silice Atom that dare even to "dance" with the ultraviolet "hot and sexy" light. I let you imagine what follows... all we know is that ultraviolet light never gets out of the weding room of the Silice atom Window... and that the Window gets fairly HOTER! So i hope you will more than understand the idea, but also that everything can be made very simply understandable. It is just a question of finding the inlightning words to make the "space" between two mind, suddenly "transparent" to the inlightning idea! It a question of letting the words and our spirit alive to catch LIFE insted of dead momies!
Being stupid, or just not indoctrinated into the notation, there can be nothing but local symmetry on a BB hypothesis. That reduces Bell's violatons of inequalities to a possibly tangible but not universal principle; an epi-phenomenom. I hate to quote Lee Smolin here but: "One problem with the use of symmetry as a route to unification is that we must then explain why the symmetry is broken. This can make the effective laws which appear to govern our universe contingent- as they are consequences of a particular solution which breaks the symmetry spontaneously. The problem of explaining our observedlaws is then pushed back to a question of initial conditions, because different solutions may lead to different symmetry-breaking patterns. The limit of this line of thought is string theory, which comes in an infinite number of versions depending, in part, on the symmetry-breaking pattern coded into the geometry of the extra, compactified dimensions." Taking us into the land of Fae or Fairy, we end up with Big Bounces, Multiverses and 2-dimensions ruling three, the Holographic projection from the boundary. Smolin would like to set up Time as fundamental. Others want the quanta,, It from Bit. As far as I can see, the fundamental theory is Entropy. ENTROPY PROVES GOD; we started out, humanly, as pristine, cosmically as nothing, the infinitesmal if you like, just as in a BB scenario; and we're complexifying, congealing, running down to Absolute Zero, temperature wise. Anyone going to deny that with a CMB at 2.725? My point is, irrefutable logic, if we're running down we were wound up. Fine-tuning and the Fine-Structure Constant exclude a Goldilock's effect. Even Sir Fred Hoyle realised that, and postulated a then unknown resonance in Carbon. As regards life, over 5,000 enzymes don't just get together in their little warm pond or lagoon to key and lock amino acids. String theorists and evolutionists stretch credibility, my credibility, to beyond breaking point. But what do I know? Anyone can use fairytales, i.e. untestable or/and unbreakable theories, to set up their hypotheses. 2 + 2 doesn't equal 4 in 3-dimensions.
+bin don Just keep in mind that personal interpretation of physics is not physics. If you think "entropy proves god", publish in peer-reviewed journals please. If you cant get published your claim is probably just that - a claim.
“No man in all Israel was as handsome and highly praised as Absalom. From the sole of his foot to the top of his head, he did not have a single flaw.” 2 Samuel 14:25 💕
System has inherent eigen vector (state) and apparatus (measurement device) its own. So, its combination of those what you measure by eigen value. You never fully know eigenvectors by statistical nature of system. Every measurement put system its most probable state of measurement of property for outcome of side effects you measure to include or exclude in reality being they orthogonal or not in mathematical sense or in mixed state. Never sure! Commute every properties to get unique one to measure for 'true' phase outcome. Phase differences matter for measurement, not overall phase relative human made reference point. Number system is the most inertial frame of reference system abstraction human ever invent to handle past, nowadays and future, but can cosmos be described by human numbers only?
some say he's wonderful, some get bored and switched away, then I have to say I'm gonna read a book even at a rate of 12 pages a day it'll be far better.
![Blox Fruits Dragon Rework Update [Full Stream]](http://i.ytimg.com/vi/EqDAp8udhm0/mqdefault.jpg)
The first hour of this lecture might be the best higher-level crash course in QM to be found. Very well presented.
I have to disagree. It has some useful ideas but there is a lot missing. It is just a quick lead in to subsequent material. He is getting people used to working with operators.
This man is an incredible teacher, he makes even the most abstract concepts approachable and understandable.
He makes them sound trivial, like eating a pizza slice by slice!
Prince Istalri
One of the greatest friends and admirers of Feynman has to be this smart and great at explaining don't you say? ;-)
Agreed
I agree, even the Avg American with a working brain can understand it!
Lenny, you are the kind of wonderful genius that makes such a difficult topic so accessible. Your natural warmth makes one absolutely ENJOY your lectures. Can't do better than that! There ought to be a "Professor Lenny Susskind" commemorative stamp. One of my very favorite American heroes!
I cant believe this material is so freely available and good. Just like being back on my course 25years ago but this time I can pause the vid to try and get my head round it all (again!). Students today dont know how good they got it :-)
We know my friend, we know
There is no doubt about how good we have it ...i thank the "giants" upon whose shoulders i stand daily :)
neil u because it’s the anti electron which by the conservation of momentum and lepton number is required to be opposite in charge ...we also know that when a positron and electron interact they annihilate one another and produce a photon of light which only happens with particles of equal but opposite charge
neil u check out the first chapter of Griffith’s intro to particle physics ...it is approachable even for the novice to particle physics
neil u spin is also involved ...fermions have half integer spin ...by the Pauli exclusion principle the two fermions cannot exist in the same quantum state or in other words have the same quantum numbers simultaneously ...field theory uses second quantization to handle this through creation annihilation operators and slater determinants to ensure anti symmetry
One of the best Physics prof. He breaks down complex things and makes them so easy to understand.
What I love about Prof. Susskind is that he not only shows us the Mathematics, but also tells us the meaning of the Mathematics. That kind of understanding is difficult to get from texts.
True
I can't believe we have the likes of Leonard Susskind's to teach us so freely, i think it is amazing that these Goliath's of science aren't much more appreciated.
I love this stuff being available to everyone. RUclips is the modern university.
It took me until minute 15 to decide "ok. This is going to be really interesting". Thank you Susskind & Stanford for putting these on youtube. I hope I can grok it.
wow, thanks! I just don't get enough of quantum mechanics during the day. :o)
Just in time for the holidays! Dr. Susskind, if you read these comments, I have greatly enjoyed all of your lectures.
Rehearsing QM formalism; Symmetry 1:02:45; Symmetry operator is Unitary 1:09:00; Symmetries commute with Time evolution and hence with Hamiltonian 1:16:30; Discrete and Continuous symmetries 1:23:30; Generating function is Hermitian and commute with Hamiltonian 1:25:30; Translation symmetry example to derive momentum operator 1:29:00
Quantum physics is something abstract at least in our daily routine life that always needs to be imagined. Here Prof. Leonard Susskind visualizes so many simple known mechanical facts in quantum, therefore, everyone even those with a little level of physics understands them very strongly.
So you didn't understand the first thing. Well, he didn't explain it well. ;-)
i lost him when he put the marker on the board
i lost him when he said his first word
@@usaviation2281 I can keep up with what he is saying, does hurt the brain a little but in a good way.
bruh me too
Can't believe a lecture on advanced quantum mechanics has over 100 000 views... Not a dancing kitten level, but still there is hope for humanity.
You see, there are many Indian and Chinese..so...
Not Interested haha, I'm Arabian.
there is hope. but in the year 3000.
you can undestand even economy with quantum mechanics!!!
since is related with maths and stadistics and many more.. time travel, bilocation, nature..
Don't forget Computing and communication. Computing is everywhere. To tell nothing about communication. QM is gonna give us Quantum computer and Quantum communication.
Awesome vid!! Thank you to this professor.. he does an EXCELLENT job of teaching new concepts!! I’m a hobbyist, and enjoy watching these in my spare time to learn more about the world and how it works. Very informative and much appreciated.☺️👍🏾
Wow. I just graduated 5th grade and wanted to expand my knowledge on quantum mechanics to prepare for middle school. I think that this video was a great lesson and I look forward to watching the rest of this series.
Bruh
1) Review 00:13
2) Unitary time evolution and generator of time evolution 29:38
3) Translational symmetry and its generator 1:02:36
Next: Generator of Rotation and its generator.
Lenny is a down-to-earth version of Dick Feynman, who could be too brilliant for everyone else in the room. He's an excellent teacher who never resorts to hand waving, but follows through with clarity on every detail. If you are one of his students, and are willing to do the work, I would expect that he would make sure that you succeed.
I am 13 and I love this stuff. Don't say it is boring, because it is not. Quantum mechanics opens up all kinds of possibilities. Quantum computing for example is just one of the many uses of quantum mechanics. The amount of possibilities is almost as mind bogeling as the psysics itself.
Ginny Armstrong 🤓
You are 13 already? Dang, Im only 3 years old and yes all those equations are so interesting. I love quantum mechanics. I already have 5 published papers in quantum physics. Excited to see what the future holds
Great revision of the QM1 course.
@1:19:33 For the first time QM matches common sense:
Q: "What requires V to be unitary?"
A: "It is an assumption that symmetries of nature take orthogonal states to orthogonal states... that seems plausible..."
At a minimum, you should watch his Classical Mechanics lectures followed by his Theoretical Minimum (quantum mechanics) lectures before this one to get the most out of it. You should be familiar with the product rule and chain rule of differentiation, integration by parts, basic matrix algebra like dot products and determinants. Familiarity with Fourier series and transforms helps a lot also.
this content is so superb that I want to put it on my cv 🤣❤️
oh my lord, I cant watch this right now, since My final exam in Account is within a month, But this is so tempting. I have been doing lots of self study, never in my dreams expected this is to be so freely available. .
I just hope this doesnt get removed any time soon.
1:15 It's easier to remember as a "commutative diagram" (as mathematicians say):
|s1> -- U --> |s2>
| |
V V
| |
v v
|s1p> -- U ---> |s2p> or UV = VU
you mean 1:15:00 ?
That's exactly what he drew
I read about orthogonality
But no one explained it as this professor did
He is just incredible
I didn't believe these complex concepts can be explained so simply..... I was stranded in the deep woods of QM but Susskind's lectures are a source of light......... here I practically see einstein's words 'only he who understands can make others understand' ... btw these are the inverse of Einstein's actual words...
This is the part of RUclips where we sift out the real fans of Physics and those kids who pretend to know physics after having watched Interstellar
Rex Galilae interstellar has manny flaws - some are only in sci-fi.
No, you should specify "Marvel Kids".
How do u know they're faking it?
I'm only 14 and studying this stuff
Lmao, I had a kid like this in middle school, he would use fancy words that he didn't know the meaning of after watching a simple physics video and when asked what they mean he would just say "oh you wouldn't understand".
I DON'T UNDERSTAND ANYTHING!
But it is interesting nonetheless.
***** no, watch videos of simpler concepts, buy textbooks for those concepts, do the questions until you fully understand, then rewatch this video.
It takes some time to unlearn concepts that you grew up with and are considered 'common sense'.
If you watch the "MATH YOU NEED FOR QUANTUM MECHANICS" lectures first, at least the mathematical terminlogy becomes much clearer.
vincent
can you tell what type of math is really needed in QM? calculus and differential equations aren’t enough for it?
@@xOxAdnanxOx Differential equations are really only needed if you want to solve particular problems. Mostly (abstract) linear algebra.
Excellent he's back!
Why can we just change the signs at 47:32? I get that we want the G^hermitian = -G to become H^hermitian = H, but wouldn't that affect the U(t)psi? thank you!
We add the imaginary number i because by definition U^dagger means to transpose the matrix and take the complex conjugate (also known as taking the Adjoint of the matrix). So if H is real, we can;t just change the sign of H by taking U^dagger; that is,
if
U = 1+eH and H is real,
then
U^dagger = 1 + eH.
But if we add an "i" in front of H then when we take the complex conjugate we actually get the sign change we wanted, that is,
if
U = 1 + ieH and H is real
then
U^dagger = 1 - ieH.
Of course, the Hamiltonian is complex because H = -ihp^2/2m + V(x) = -ih/2m (d^2/dx^2 ) + V(x)
but -H does not equal the complex conjugate H* (to see this multiply H by -1, then actually take the complex conjugate H*. You'll see that -H does not equal H*).
how far does this professor walk every session?
Hmm, Lets do poors man calculation. Videos are generally 2 hours long and assuming he stands for 1/4th the time to explain stuff and other 3/4th the time walking and writing on the board. So total time he walks is more like 1 hrs 30 min. Now assuming an average walk speed to be 1m/s. Calculating its in hour gives us 3.6km/hr. Now hence putting it in vt=distance we get, 1.5hrs*3.6km/hr=5.6kilometers each session. Hail lord fermi.
If you want to follow along with Sakurai's Chapter 4, start at 1:20:00 ish.
Can someone explain why these lectures (and other videos) are posted many times on RUclips - by Stanford but also by lots of other people - when you view them they seem to be exactly the same ones.
Why do lots of other people publish the same stuff? - what's the point?
I think only stanford has posted lectures but too many people have created playlists
Most of these students asking dumb questions should revise prior to doing Advanced QM. Both Heisenberg matrices and Schrodinger pictures are required in QM as the first describes the discrete quantifiable eigenvalues of the eigenfunction psi whereas the Schrodinger picture describes the continuous picture of a quantum picture. Schrodinger picture is always the initial state of a particle. The Heisenberg picture better describes measured states like angular momentum, spin etc ie values of observables
Very interesting! I love prof. Susskind, especially when he eats his cookies! I've been attending all his lectures, It'll take years... :-) thank You prof!
25:20 He said that Ψ(x) = , but in the momentum eigenvalue equation he simply replaces |Ψ> with Ψ(x). Why?
59:15 The definition of the time independent Sch.Eq. that is the eigenvalue equation, beautiful
Just finished binge watching Rick and Morty, this all makes sense to me now
I watch these to fall asleep but it’s too interesting and I stay awake 😮😮😮😮
Absolutely phenomenal lecture. Very clear and concise.
75 this year? going strong :) keep up with good material.
just came here to get mind blown...MIND BLOWN!!!
56:20 Beautiful derivation of the Sch. Equation
Can we not do an observational experiment of a partical of position n momentum at same time to then get both its position n momentum, why can't we observe both simultaneously dule experiment on same partical thus defeat this idea of can't know both, it's one or the other, seams can use a pc to calculate math if take calculations of partical at multiple spots then give position and it momentum...?
You can measure both at the same time. What you can't get is the same values every time you do this measurement. There will be a considerable uncertainty in the statistical distribution of these measurements.
I put on my clothes, C, and multiplied it by my morning tea, T and then added a generated number, G, which I got by subtracting the symmetry of how many seconds it took to tie my shoes, S, and I got the translation of how much traffic there will be on the way to work, as a wave function, W.
who would put a thumbs down? i dont understand jack but i love this..why a thumbs down? someone who loves biology?
Lol I'm also curious bout this
Im gonna be honest, I leave this on in the background because I can't possibly comprehend what he is saying and it is helping me get work done. LMAO
In 44:48 , what requires this operator to be Hamiltonian? Shouldn't any Harmitian operator be just fine?
I don't think he proves that here, but the hamiltonian corresponds to the energy of the system. It appears in the time-dependent schrodinger eq which in turn comes from the assumption that the evolution of the system is governed by some operator which is to be close to H for small time spans. Its just a matter of where you create it and where it is significant. idk if this is exactly what you asked. ruclips.net/video/tRWBoossG0Y/видео.html could help too.
4:20 complex numbers are ubiquitous in quantum mechanics - so does that mean that the square root of a negative number is the only way to explain it
I don't know why you guys are here but I am here so i can sleep
You should be in bed
Please, no translation, but reproduce down or above the screen the lecture. Thanks
Where is the full couese available online?Can anyone plz tell?
Curious about the choice of words orthogonal versus linearly independent?
Orthogonal means the scalar product of the two vectors is zero. Linear independence means that no linear combination of the vectors is the zero vector.
In the part where he talks about conservation of information, why does he insist on 2 states being observably different being the same as the 2 states being orthogonal? Aren't two states that aren't multiples of each other but with non-zero inner product still observably different? What am I missing? Thanks!
He talks about it at length in his basic QM course. In short, when we perform a single measurement of an observable Q, we can only get one of its eigenvalues a, and then the state of the system collapses to its corresponding eigenvector |a>, meaning that the previous state is irreversibly lost. We say the states |a> and |b> are 'observably different' when threre exists an observable Q, such that after measuring Q we can say with certainty whether, before the measurement, the system was in state |a> or in state |b>. Due to math, this condition is equivalent to |a> and |b> being orthogonal - when they are, we can possibly craft an experiment to distinguish these two; when they are not, such an experiment cannot exist even in theory.
A practical example is the spin of an electron. We can easily measure between electrons in an |↑> state and a |↓> state, but there is no possible way to reliably distinguish between electrons in an |↑> state and a |→> state, because they are not orthogonal, |→> = (|↑> + |↓>) / √2
At 1:08:40 he says that the operation might correspond to squeezing or stretching, which are not symmetries. But then a few seconds later he requires that V be unitary. Did I miss something?
He uses V in the first case to say that doing anything corresponds to multiplying on the left by an operator. Next he is talking about operators representing symmetries, and he uses V again, a particular case of the first V. It's commonly done in mathematics, called AOL "abuse of language"
Remember it’s not about whether you can read sheet music, it’s can you hear it. Can you hear the music Robert?
at 1:26:24... those(H & H dagger) are hamiltonians and not hermitian
how to visualize a wave function ?
it will be helpful in contribute to the development in QM
dear professor can you please enter the English subtitles in his last lessons on the internet. Thank you
in the G deduction: (1+epsilon*G)*(1+epsilonG*) = 1 becomes
epsilon(G+G*) + epsilon^2 (GG*) = 0
but he says:
epsilon(G+G*) = 0
Why the epsilon^2 (GG*) term vanishes? is it too small, as epsilon is a small amount of time?
sorry, later says: ignore the epsilon squared its too small
@1:35:04 how is shifting to the right not + epsilon? but - epsilon instead?
Would it be possible to get the lecture notes of these lectures?
I am still trying to find out WHY group theory is necessary to do quantum mechanics. Anyone help me?
Edit: His last sentence in the lecture said the symmetries that do not commute with each other have real power …. More to the story I guess. But still wonder why groups are NECESSARY.
Because nature has symmetries and symmetries are causing conserved quantities and in real QM conserved quantities is all you ever care about.
Didn't understand this lecture, I have only completed A-level maths is this enough to understand this course?
No
I suddnely opened the video. Can anyone tell me is it langauge speaking class and which langauge he is writting on the board??
Where can i find the lecture notes, thanks
I dont know
which book he is following?
jyoti baadal yeah im not sure either lol. Are you phys major?
The only bright thing in 2017 that's not something god forbid, is being able to study advanced quantum mechanics from freaking youtube. I'm now half an hour into the lecture and i did watch a thousand documentairies on this, but i still had to go trough almost 20 wikipedia pages to nearly understand half of what he's saying. I'm not stupid but i didn't realize that even considering an actual thought about this subject requires a lot of skill. Skill i've got to catch up to. But it's still realy amazing to find this kind of knowledge out here.
At last why psi(x+€) is replaced by psi(x-€) ? Displacement was toward right side.
Graph out x^2 and compare it to (x-1)^2. Watch that it shifts to the right. So a right shift on f(x) is defined by f(x-a)
Every time I get full of myself and think I am knowlegable, I watch a video like this and realise I know nothing.
Its tough but it give it time ull get it!
sir I need problem solution chap first of modern quantum mechanics by j.j sakurii edition first.can u help me in this??
fabulous, here is just a basic lesson about the quantum mecanic but we can see already a implied reference to the "pullback" property (category theory) and a allusion to the "Noether" theory
I’m listening to this tonight because I have insomnia and want to fall asleep
question: Do the symmetric transformations take up time?
Physically transformations take time. It takes time to, say, rotate and object. But mathematically we consider operations happening independent of time; that is, for a rotation of phi radians, R(phi) we only consider the change of the state with respect to the rotation;
R(phi)|psi> = |psi(phi)>
where |psi(phi)> represents the state |psi> rotated by phi radians. So, mathematically, we treat the rotation as happening instantaneously.
No time. The point is you are rather translating/rotating/etc. your frame of reference.
does the time operator (U(t)) is a symmetry?
If H does not explicitly depend on time then yes. This is because U(t) is constructed as a Taylor series in H. Therefore U(t) always commutes with H. The consequence of this is that energy is conserved in time.
For a H that explicitly depends on time it is more subtle and I am not educated enough to give the answer.
I know this is 8 years old but I thought it may help someone else.
missing subtitles. You can insert them?
you found a subtitle ?
can we get the lecture notes or they aren't available?
Is there a better introduction to this class?
Nobody does it better than Leonard "Leonardo" Susskind, makes me feel sad for all the rest. Why'd you have to be so good.
Just revisiting my 1st grade math class.....
i just typed in advanced ohysics and never did physics before and understood a lot. I wish german schools were like this
German schools are like that. Some are even better. Susskind is not very good at teaching the basics.
Ok so some people say that 13 yr olds cant get it but its really interestinf to me thos im thirteen and im understanding this fully tho sometimes a bit hard but yea i do and i just began advanced and would love tips from some quantum mechanic gods please and don't say "u cringe u probs dont know 2+2 " Keep yapping u probs dont get it urself
Ive done the basics
Ik what maths to learn (integral calculus etc etc) dont make fun saying ur just 13 dont do cuz i want to i reallly want to and i shall if u cringe, leave and do whatever u wanna
Quantum mechanics gods please i need some tips please just for future
Shelly Das not just integral calculus but calculus 3 and partial differential equations as well
You also can’t just skip to quantum mechanics, you have to do classical mechanics, electrodynamics and maybe even some relativity before even starting quantum mechanics.
@@jaykay2218 ik man this is the problem i wrote etc man just cuz im 13 i cant do it? The heck i already did classical mechanics
@@jaykay2218 i did it man i stated etc
@@jaykay2218 btw could i have tips thanks
"Someone" should make a comments list on Henri Bergson so-called Philosophy of Time, for example what,how and why is it not simply just another interpretation of the Arrow of Time and Relativity in the Correspondence Principle format.
In the ONE-Infinity unity-connection categorization of e-Pi-i logarithmic resonance Partitioning of self-defining temporal phenomena, a musical-pure-math continuity to instrumental device idea.., the image of conic-cyclonic quantization cause-effect is an aspect of ONE-INFINITY Singularity Quantum-fields Mechanism Holographic Principle.
Some math-musical thinking practice.
Can someone refer the vector to the operator?
The thing about QM that i dont like is that you never know H. And if your experiment is different than expected, you just try a different H, until it eventually explains the observations. Its like a theory with a parameter that you can guess, you may aswell just guess the results. At least thats my feeling at the present.
+phil durre All theories are like that. You have some equations, some constants, some rules, and you try different ones until theory matches.
The crucial thing is that once it works, it works all the time within its range of applicability, which NEVER is just one particular instance of an experiment, which would be equivalent to "introducing the results by hand" or "guessing the results", as you described it.
Can you add Turkish subtitles i Love Quantum mechanische But i cant understand english
Hm.. Asked a question on a previous lecture a few minutes ago. I think this answered it. Re-watching this to prepare for the coming thesis ;) I recommend everyone do the same. Brush up on your understanding of "how read this and see where it should envelope". Might be released tomorrow if tonight is right lol ^^ Check sci-journals. Thanks LS
Glossary of associated e-Pi circularity and i-condensation superposition identification of conventional-temporal phenomena.
(Preliminary "sufficiency" analogue to comprehend time-timing sync-duration identification)
Hermitian Operators are Real Number, Quantum Theoretical, temporal superposition real-time associations.
abstract Quantum numberness vector-values.
Eigenvalue Hermitian Operators-> (quality of floating frequency?) multiplies (amplitudes?). AM-FM Communication?
"Orthogonal", ? approximately "the illusion of separation", (phase-locked?) between quantization identification vector-values (Singularity positioning integration?)
Zero-infinity 1st law of thermodynamical orthogonality, because axial-tangential Geometry, 2nd law point-line-circle time-timing e-Pi sync-duration i-reflection phase positioning-location conic-cyclonic condensation, Eternity-now Interval Reciproction integration, in Singularity-Apature Perspective Principle.., is holistic holography, vector-values dimensionality. "Recording" or Imagery.
"Wave function times its Complex Conjugate is always positive", (intuitive convention provision), because multiple, superimposed vector-values, are real-time potential possibilities and probabilities, existence sync-duration, multi-dimensional connected, (observable-> n D dominate probability vector-values), Condensates mass-energy-momentum continuous creation cause-effect connection. Operational Principle of Calculus eg Chain Rule => Dimensionality coordination.
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Students should choose their own reiteration and reintegration patterning. "Yesterday is gone".., and never was..
❤Thank you very much Professor and class
yes, i will be busy all tonight!!
Christmas came early this year! :)
This professor's name is Leonard Susskind. I will check him out in RUclips.
I am 11 years old and i understand none of this
I'm 20 and I barely understand anything.
38 .....huh???
Nancy Witt
that's coz you're 11 years old and are watching videos completely unrelated to your age group XD
Btw, I'm 18
Well I preferred Tom n Jerry to Advanced Quantum Mechanics at the age of 11.
You don't quit it. One day you will get it.
@Nancy : I'm curious what drove you to listen to such lecture Nancy. I find it interesting because Qantum Physics could definitely be taugth to young students curious and open mind. But these lecture are NOT GOOD, even for avanced level. Fundamental ideas and assumptions are ill defined and not justified. Fundamental mathematical structures are treated like most physicists does, that is like tomato sellers leaving the mind in a total jam! And worse almost no crucial historical experience are reworded making the hall lectures a mountain of arbitrary words and concepts. The entire lecture stands like a trunc of a tree without any roots nor branches. It's thus a pitty that curious yought don't understand anything in such lectures, it is a sign that IT IS NOT CLEAR, even to more advanced ones that illusory believ they understand fairly more. The PHYSIC should be cristal clear even if the subject is chalenging, even to a young mind if the course was CLEAR, and finaly besides the mathematical level (if it was done properly) that woul of course chalange you (but that also can be tuned and wisely adapted to young people or amateurs, it's a question of pedagogical skill, but everything IS POSSIBLE if the will is there!) But keep in mind one very important point : that Science is like a stairway, very difficult to climb if you haven't to only climbed but insighted the previous stairs that build your Modelisation Power of World Phenomenology. And to leave you with a insightful hint Quantum Physics is a Mathematical Model (ie A PRECISE AND POWERFULL FORGED TOOL TUNED FOR EFFICIENT CATCHING OF REAL PHENOMENOLOGICAL BUTTERFLYES AS OF THE MORE SUBTILE MYSTERY OF THEIR WAY OF BIRTH, TRASFORMING, LIVING, FLYING, FLOWERING, REPRODUCING, DYING...). To leave you at least with one precise and concrete situation where Quantum Physic Mathematical Modelisation is deadly needed to catch what is happening. A simple WINDOW offers us a usefull TRANSPARENCY because SILICE atoms from witch the glass is made ( contrary to most other atoms constituing mater), do not dare to play, to talk, to hugg, to interact with the incoming light, falling from the sun and springing from surroundings. And so, THE LIGHT PASSES the Silice mater, bringing thus the light and energy coming from the sun and also the billions of rays bouncing out of all outside earth mater (trees, building etc). Thus why Silice is such an asocial atom regardless of light, why does it SNOBES it radically, is made understandable by Quantum Physic Mathematical Model. It sketches the atoms as a STAIRWAY : or you have enough energy to make at least on step and you make it or you don't. there is no "half way". Or like an apple that can't be cut in peaces. Or you have one dollar to get it or you starve. No "half way". And the final key to understand is that Silice atom make their PRICE SO HIGH that visible incoming light dare not pay even a smile exchange with the Silice atom (very rude!!!!). But ultraviolet light (more "sexy" than visible light, more "hot", more "energetic", more "rapidly shaking it's belly") succeds in seducing this selective Silice Atom that dare even to "dance" with the ultraviolet "hot and sexy" light. I let you imagine what follows... all we know is that ultraviolet light never gets out of the weding room of the Silice atom Window... and that the Window gets fairly HOTER! So i hope you will more than understand the idea, but also that everything can be made very simply understandable. It is just a question of finding the inlightning words to make the "space" between two mind, suddenly "transparent" to the inlightning idea! It a question of letting the words and our spirit alive to catch LIFE insted of dead momies!
Being stupid, or just not indoctrinated into the notation, there can be nothing but local symmetry on a BB hypothesis. That reduces Bell's violatons of inequalities to a possibly tangible but not universal principle; an epi-phenomenom. I hate to quote Lee Smolin here but:
"One problem with the use of symmetry as a route to unification is that we must then explain why the symmetry is broken. This can make the effective laws which appear to govern our universe contingent- as they are consequences of a particular solution which breaks the symmetry spontaneously. The problem of explaining our observedlaws is then pushed back to a question of initial conditions, because different solutions may lead to different symmetry-breaking patterns.
The limit of this line of thought is string theory, which comes in an infinite number of versions depending, in part, on the symmetry-breaking pattern coded into the geometry of the extra, compactified dimensions."
Taking us into the land of Fae or Fairy, we end up with Big Bounces, Multiverses and 2-dimensions ruling three, the Holographic projection from the boundary. Smolin would like to set up Time as fundamental. Others want the quanta,, It from Bit. As far as I can see, the fundamental theory is Entropy. ENTROPY PROVES GOD; we started out, humanly, as pristine, cosmically as nothing, the infinitesmal if you like, just as in a BB scenario; and we're complexifying, congealing, running down to Absolute Zero, temperature wise. Anyone going to deny that with a CMB at 2.725?
My point is, irrefutable logic, if we're running down we were wound up. Fine-tuning and the Fine-Structure Constant exclude a Goldilock's effect. Even Sir Fred Hoyle realised that, and postulated a then unknown resonance in Carbon. As regards life, over 5,000 enzymes don't just get together in their little warm pond or lagoon to key and lock amino acids. String theorists and evolutionists stretch credibility, my credibility, to beyond breaking point. But what do I know? Anyone can use fairytales, i.e. untestable or/and unbreakable theories, to set up their hypotheses. 2 + 2 doesn't equal 4 in 3-dimensions.
+bin don Just keep in mind that personal interpretation of physics is not physics. If you think "entropy proves god", publish in peer-reviewed journals please. If you cant get published your claim is probably just that - a claim.
This is going to be good.
“No man in all Israel was as handsome and highly praised as Absalom. From the sole of his foot to the top of his head, he did not have a single flaw.”
2 Samuel 14:25 💕
I know His perfectly Proportion
He is God
System has inherent eigen vector (state) and apparatus (measurement device) its own. So, its combination of those what you measure by eigen value. You never fully know eigenvectors by statistical nature of system. Every measurement put system its most probable state of measurement of property for outcome of side effects you measure to include or exclude in reality being they orthogonal or not in mathematical sense or in mixed state. Never sure! Commute every properties to get unique one to measure for 'true' phase outcome. Phase differences matter for measurement, not overall phase relative human made reference point. Number system is the most inertial frame of reference system abstraction human ever invent to handle past, nowadays and future, but can cosmos be described by human numbers only?
That's a lot of handwaving to get to the wrong conclusion. :-)
I want your help in M phil how can i contact you
Hardest part is the Leonard Equation, I still haven't solved it.
some say he's wonderful, some get bored and switched away, then I have to say I'm gonna read a book even at a rate of 12 pages a day it'll be far better.
Depends on what you are looking for.
I love this guy... AMAZING.