Quantum Mechanics Concepts: 1 Dirac Notation and Photon Polarisation

Part 1 of a series: covering Dirac Notation, the measurable Hermitian matrix, the eigenvector states and the eigenvalue measured outcomes and application to photon polarisation

[@ashkara8652]

Seriously, who are you. I've learnt God knows how much of the most complicated of topics from you and I have no idea who you are or what you look like. If Paul Dirac was brilliant for finding such useful notations then you certainly are brilliant in explaining all this beautifully.

[@adamfattal468]

He is called Prof. Bob Eagle (he is also a singer and a soccer fan). His twitter is @BobEagle2.

[@ashkara8652]

Thanks man!

[@enricolucarelli816]

Yes. I fully agree. Absolutely fantastic. Who needs to go to university in search of knowledge if these superb lessons are accessible in KZbin? Thank you very much!

[@jeromemanceau4263]

Same from me. I wanted to get a bit deeper into quantum mechanics for fun, but needed some help to get started with books like the "theoretical minimum". You're a perfect teacher. Thanks!

[@pcalculas]

He is The Great Dr. Bob Eagle CBE

[@meniscusmedical2471]

When you've spent ten years having to understand dirac notation and in the space of 5minutes you get it, it goes to show it's a great teacher that makes the student great.

[@hanniffydinn6019]

It’s just short hand to help describe vector hilbert spaces. 😯😯

[@hanniffydinn6019]

Hugh Jones you miss the point, it’s a leap in thinking when someone comes up with new notation that makes more sense and elegant. These things are important landmarks in mathematics. The OP is correct, they aren’t Taught the significance and reason behind the notation. People learn this afterwards in their own time. It’s weird really. I’ve more understanding now, at university you just memorised stuff, but never truly understood,say, the notation.

[@ErwinSchrodinger64]

@@hanniffydinn6019 Yes, I completely agree. When I first took thermodynamics, I thought I understood what the equations meant. Took Thermodynamics II and realized, I didn't understand anything. Then, in graduate school, thermodynamics III, along with statistical mechanics. This time around, I memorized, worked out problems, understood the experimentation. Thus, I understood the mechanics but I couldn't tell myself whether I truly understood it. Taught thermodynamics several semesters, and slowly, based on what I learned, I began interpreting the meaning in way I could personally understand it form my vintage viewpoint and it clicked. My interpretation is not any different nor is it a leap forward. I finally accepted, at face value, what thermodynamics entails, from a personal view, that is consistent with everything I've learned. You have to internalize the theory, equations, and so forth before you can began to understand its motivations.

[@schmetterling4477]

Don't know about you, but it didn't take me more than a day to understand that in QM101. That is not the hard part about quantum mechanics. ;-)

[@DrPhysicsA]

I did nuclear physics and got my PhD from King's College, London.

[@pinklady7184]

Do you ever use 3D softwares to make physics simulations?

[@jhumasarkar5203]

@@pinklady7184 he will never answer you because he left KZbin 6 years ago.😭

[@almightypush6888]

I got PhD in partical physics at the university of cambridge

[@pinklady7184]

Jhuma Sarkar He is probably dead.

[@almightypush6888]

@@pinklady7184 wallahi

[@ahmedwaly9073]

This is the best lesson I had in my life

[@executorarktanis2323]

True

[@whythosenames]

we are profile picture buddies

[@DrPhysicsA]

Thanks for kind comments.

[@JimmyGray]

I wonder how many young ( and not so young) physicist have been inspired by your gracious and well thought out presentations. Thank you!

[@kamrankhademi]

Thank you, DrPhysicsA. I love everything about your videos: Clarity, brevity, pace, your drafting, and even your felt marker!

[@benedicterhardt5594]

I love your grammar.

[@kevinkowens]

I am so grateful to you sir for your contribution, your passion and love for physics and help for a physics major like myself to navigate such a beautiful and elegant subject. I wish there were more people like you in this world who are willing to give of themselves with the magnitude of Excellence that you bring. I just wanted to write a little note of thanks to you and I wish you the absolute best

[@kadamati284]

An amazing introduction! What i didn't understand in years is clear now within few minutes. I owe you a hundred coffee, Professor. Thanks.

[@st1cummings873]

Kvy

[@JonathanLangdale]

One of the best ways I have seen this explained. Nice job.

[@rsaleh8957]

Master class! How can you take something so complex (pun intended) and make it so real (also intended)? Pure magic. This video is must-see TV for us quantum nuts. The textual corrections are funny and make it even more compelling.

[@alliejoan5145]

This video made sooooo much sense. Thank you, you're an amazing teacher!

[@DrPhysicsA]

Thanks. All good wishes for your studies.

[@CNCichon]

thanks for teaching me even if i'm twelve

[@samarthsai9530]

Thanks a lot sir. Please explain to me that why we use matrices to represent something which is observable(What is the connection between them?).

[@rashahameed4937]

I from Iraq

[@thesoccer02life]

This is exactly what I needed. So many professors assume that at this level of material they can skip all of the basics and us students will know exactly what they're talking about and that we know all of the elementary math and physics behind it. Definitely not the case. I always have to go back and review the basics. YOU ARE AMAZING. Thank you

[@RawringAtYouNoobs]

Great video! I've been struggling to understand Dirac notation for a while. I never realised there was such fundamental mathematics behind it until now!

[@hansfijlstra5932]

What an excellent video! You are a genius in finding the optimal balance between explaining detail and concept. Only truly exceptional teachers have the skills of doing this. A lot of teachers can and should be replaced by this kind of high level video tutorials combined with good books. Would save a lot of money and time! Again excellent!

[@DKonigsbach]

This wonderful series of videos fills an important gap. There are other videos on KZbin that give you high level concepts with no mathematics. There are also videos on KZbin that give you a deeper understanding, showing the mathematics, which throw you into the deep end of the pool and expect you to sink or swim, as if you should have to prove your worthiness of learning this. But THIS series of videos gives you a deep understanding, including the mathematics, while trying to make sure that you WILL be able to follow it and WILL come out understanding it. This a great way of teaching!!! If you are coming to this subject without a lot of background, then these are the videos that you want.

[@wreza97]

7years, and this video is still the best! Thank you @DrphysicsA for doing what you did.

[@mathcritic]

What a fantastic video! No muss, no fuss, no quantum hype, just the facts. Nice job Dr P!

[@mehmetaliyagc2092]

I'm watching all your videos and also nearly all other people's Physics and Quantum videos in internet.You are the BEST ever.Sometimes you are admiring Prof. Susskind from Stanford but i watched also all of his videos.They are not even comparable to yours...I also ADVISE to people who stupidly criticise you here and try to show that they are clever and know sth.....''Please make your own videos and let us criticise you also..I wish they learn to appreciate and thank to this perfect teacher, at least for respect ''...Hope to see your new videos,amazing teacher,..thanks for all !

[@sina8883]

Thank you drphysics for these wonderful videos. They have really catalyzed and facilitated my interest in areas of physics which previously had seemed hopelessly out of reach. These were just the footstool I needed to bring them into reach for me. This is a great public service you have done and you have our gratitude.

[@paulbaker916]

It's taken me 6.5 years to find this video however I'm very, very glad I did. A brilliant no nonsense, personable, informative hour that even had subtle humour. As others have said; much of the nomenclature was familiar however within a very short space of time many vague concepts and thoughts began to gel. Looking forward to watching the rest of the series. It's work like this that makes KZbin great. Thanks for producing this.

[@wojpaw5362]

Thanks to your videos I passed my A-LEvels in maths and physics. Now you save life again in my 3rd year quantum mechanics module. You're amazing

[@sclair2854]

Thank you so much for the short review of matrices. A little revision at the start always helps me pick up the newer stuff easier.

[@joeclaxton99]

I've spent years wandering about in the dark wishing I could find my way in to Quantum Mechanics and Quantum applications such as Quantum Computing whilst holding down my day job. Now, finally, I've found the door handle and the light switch. Thank you so much DrPhysicsA, very much appreciated!

[@yetian]

This is the clearest explanation of Dirac notation I've ever heard of. An awesome lesson!

[@neoutopiamessiah3]

Thank you so much for your thorough yet simple and step by step approach to something often made unnecessarily complex. Well done.

[@ngyufeng6205]

Amazing! Clear as a crystal and still understandable even for laymen. Great job! Thanks!

[@muddassirghoorun4322]

The best explanation i got so far... Thank you and keep up the amazing work!!

[@Patrick-cy2zh]

You should have a Nobel prize for being a great teacher. Even me, Patrick Star can understand this subject because of you!

[@veikko91]

Why am I seeing this only now and where have you been my whole life? Thanks for help!

[@SaschaTayefeh]

Thank you so much for all your effort explaining, recording and sharing with us!

[@lwskiner]

This is the first time I have heard a simple definition for eigenvalues and eigenvectors yet. That alone is worth the value of this presentation.

[@alanatlantistv]

I hope this channel wil stay on line forever. It's so good

[@Gismho]

Yet another excellent exposition of QM mathematics. Thank you!!! (This should be prescribed viewing for all budding physical science students.)

[@fractalized3]

Probably the best physics lesson i have ever had in my entire life. Thanks Prof. Bob

[@TubingSD]

Oh. My. God. This just cleared up about 236.284+E25 concepts about quantum mechanics that I have been trying to get through my thick skull for the last several years. And you did it in less than an hour. Wow.

[@mireksoja9063]

Super! You explain complex topics in a very clear way. How I wish to have a such a great professor like you when I took quantum mechanics courses many years ago!

[@canlished]

proud f u sir....Big salute....... Its about 15 years m studying quantum mechanics.. lot of books, articles, physicists..... but u made the Mathematical special functions a philosophical and realistic life... n those who trying to correct you have only one intention "ONE man SHOW". N these people when explains things to students always says "its complicated and weird" an they skip n hide big concepts behind these two words..!!!! but the thing is that "If you can't explain it simply, you don't understand it well enough. ---ALBERT EINSTEIN

[@imrozzahan7328]

Sir, you are a natural teacher like Stephen W. Hawking, you are simply great. Thanks a lot.

[@gilberteswann6142]

Fantastic lesson! This is so well explained that I've been able to follow myself! Thanks so much for teaching us. This is so kind and generous of you. Thanks!!! and please, don't stop!

[@yevonnaelandrew9553]

I really need a quick quantum introduction and I found these videos are really amazing. It helps me to learn further in my self-study journey in quantum things! Thank you.

[@sreeprakashneelakantan5051]

Even after six years, this explanation is undoubtedly the clearest 🙏

[@t3db0t97]

I'm only 26 minutes through but this is already the single best QM explanation I've yet found after about 5 months of reading and watching everything I can find. Your walkthrough of linear algebra is concise and useful, and when you got to H|a> = lambda |a>, the eigenvalue and eigenfunction, everything I've been struggling with suddenly snapped into place. Amazing. Now what Prof. Susskind's "Theoretical Minimum" is saying actually makes (more) sense to me! OK now on to the rest ;)

[@peterhall7972]

Now what Prof. Susskind's "Theoretical Minimum" is saying ; NOW actually makes (more) sense to me

[@pastorericardo]

I was a little bit lost reading "feynman lectures on physics pdf volume 3" , I got stuck in chapter 10, now thanks to this gentleman I am back on track!

[@roblouw1344]

One of the best lessons I have had in my life!

[@samtux762]

Paul Dirac was a genius to come up with this formalism. Dirac was smart. But Hilbert proposed this notation to Bohr much earlier. Bohr thought that Hilbert didn't understand the question...

[@CarolRiveraL]

I agree with all the comments! Explanation is quite clear, straight and clean. I don't get lose among that amount of concepts. Funny that most people struggle trying to teach these topics but you do it like a piece of cake. Thanks a lot!

[@fernandojimenezmotte2024]

Great class ! You made Quantum Mechanics basis , very understandable and very didactic Dr Physics !!!!

[@mattmackay76]

I so enjoy watching your physics videos. You are a phenomenal communicator and teacher. Im so glad you made these.

[@NandishPatelV]

How you made quantum mechanic so accessible is amazing!!! Keep it simple :) I look at the notation now and feel elated that I understand at least some of it. Thank you!!! I'm gradually accessing maths and physics at this quantum level ;)

[@danko6yg411]

Thank you DrPysicsA. You do a fantastic job in presenting somewhat difficult material with Dirac. You make it so clear

[@DrPhysicsA]

There's a very brief description at 19:00 in my video "Atomic Structure - A Level Physics"

[@lomertamahon1]

Paul Dirac never ceases to amaze me. He is the most underrated of all those connected with quantum mechanics. He IS quantum mechanics.

[@KingCrocoduck]

You're amazing.

[@heavennoes]

you have a good channel to.

[@michaelantzoulis8872]

Absolutely incredible lecture. Turned stuff that gave me headaches elsewhere into a piece of cake. Thank you so much!

[@ddopson]

You are a great teacher, and I hope that you come back to KZbin. I went through at least a dozen different videos from various channels, including several much more popular than this one, and this is the only one that did a good job of explaining the notation, which can be one of the most intimidating aspects of QM.

[@vincentp5616]

People Like You, Make KZbin A great Resource Thank you !

[@biohoo22]

You are an amazing lecturer. I am a biologist by profession; however, I wanted to learn more of the "hard sciences" on my own. Your lectures are clear, cogent and easy to follow. You do not simply present the tedious and cliched quantum physics examples like so many other videos and stop at the results (double slit experiment, photoelectric effect etc.)--you actually explain the mathematics in a way that does not go over the heads of the majority willing to learn. Thank you.

[@rigoluna1491]

This has been the most informative pen I've ever watched.

[@waqassaeed674]

My quest to understand dirac notation has finally ended. Lots of respect Sir.

[@silvithomas]

Dr.Physics thank you.for the most clear and beautiful lectures in KZbin

[@fredrickvanriler7986]

The smartest and most consummate Professor I’ve witnessed❗️

[@manchesterunited9576]

You are the best! Thank you for taking your time to share with us this wonderful knowledge!

[@razziade]

I wish KZbin was around when I studied physics! Students now are SOOOO lucky to have this. Do you need office hours these days? Instead of KZbin, we went through stacks of physics books looking for worked out examples that were similar to the problems we were trying to solve. Students of today, don’t take these videos for granted. I’ve seen a lot that have made me understand concepts that I could not grasp back when I went through college. Thanks for all your video DrPhysicsA!

[@PeterFreedMD]

Best explanation of matrices I've ever found on the web! Thank you so much!

[@banyantree]

Excellent video - it's gratifying to be able to follow along and understand what is happening. Like others I learned more in this hour then countless hours in other courses! THANKS!

[@lucasfortier3682]

Dude, i Love you. Greetings from a French PhD student in chemistry, trying to give lessons.

[@mhd112211]

wow, i'm sure glad i've fiound this video! no one has ever been able to explain this so well to me! thank you so much!

[@marycatherine4220]

Your lectures are incredible. Thank you so much!

[@currentmuvingi5936]

now there is no need for me to go to university if i will get good videos like this, i really liked it, keep the ball rolling Dr Physics.

[@HaiderKhanZ]

Please keep making these videos for QM, you're the best teacher on youtube for this stuff!!!

[@wilrohan2985]

Another excellent video Sir. Thank you. I really appreciate it!

[@guitaringjarmin]

Absolutely brilliant explanation. You are a hero sir

[@eamonnsiocain6454]

Succinct! Excellent! Thank you so very much! My concentration was in Maths, yet my focus was more towards Epistemology than Physics. Your video explained an application which I never had had the time to explore. Again, thank you.

[@NomNomReddit]

You explained what our lecturer's going to explain next week in 20 minutes, bravo

[@rmw3hair3]

The best explanation I've come across. Great man indeed

[@monsieurneversois861]

You're an amazing teacher ! Amazing ! God bless you !

[@jakevikoren]

Thank you so much for your time. Very well and clearly taught. I appreciate you! :D

[@EditB3ast]

I’ve been looking for this video forever, thank you DrPhysicsA

[@kamehamehaDdragon]

Great video, i am not a physiscs student but i got courious, and i think i learned quite a bit, its very intresting to see the usage of linear algebra in photon polarisation, im still thinking aboout it and trying to interlace the concepts i know. im looking foward to see the second part and see how this bad boi turns out!

[@pseudohominom]

Best explanation of this ever, especially you explaining why we sue probabilities by experiment.

[@awowoosas]

This is pretty awesome, man... Thanks so much for these videos, it helps me to know where to start on Quantum Mechanics. I was so puzzled on where to begin since Quantum Mechanics is so big of a topic on its own !! Once more, thanks for sharing your knowledge :)) I can't be more thankful. PS: I really enjoyed your explanations and your constant reminder on certain terms which makes it so much easier to understand for people with rudimentary to little foundation of high level Maths and QM.

[@MrHuno92]

Who dislikes these videos anyway? ... Every single concept needed to understand was explained.

[@charleschidsey2831]

Love your clear and concise explanations. You definitely earned my sub.

[@Frogcleaner]

exciting new series! exactly what i always wanted to know but never could get a grip on. thx again prof for all the excellent work.

[@QUECWA]

Dr PhysicsA I teach quantum physics and quantum computing and I can’t tell you enough how FANTASTIC you are!!!!!!!

[@philipswain4122]

A crystal clear explanation. Many thanks for posting.

[@stella-mariest.5546]

Such a great video! I am going to show it to all of my friends!!!

[@dougmccullough2144]

Really enjoy these videos! Your presentation is so clear, thanks!

[@jo5804]

Greetings from Ecuador, thanks for share your knowledges brilliantly.

[@williamschaefermeyer7007]

I've only taken enough math to get a bachelors in business and I was able to understand this video to the very end. Amazing explanation, especially considering it was 8 years ago now.

[@tallbillbassman]

Excellent stuff, beautifully presented. Just a bit worried about the way you multiply out the bra-kets to produce a probability amplitude, a result which is not squared and which you then square all in the same equation ending up with the real probability. Root 2 doesn't equal 2. Careful viewers won't be confused, so the error isn't fatal, but no one seems to have mentioned it. You could also take a leaf out of Susskind's book, by stating that the reason for choosing Ix> and Iy> as orthogonal is that they are mutually exclusive states. This helps later on when you come to look at spin-up and spin-down states for electrons, which as I'm sure you are aware are orthogonal states, not opposites. Thanks again. I really enjoyed this. Bill Dixon.

[@judedavis92]

Amazing. Please come back! I haven’t seen a video from you for a good few years now. But thanks for these videos. Amazing!

[@abouzarazarpira8840]

THANKKKKK YOOOUUUU DR. i love the way you teach and it was exactly what i needed.

[@rhlogic]

Wowser! You are the perfect professor! I mean it.

[@007myzorro]

AMAZING!!!!!!! unovercomeable. Never heard such a clear explanation about such a complex matter. It s Feynman himself !!!!! THANK YOU SOOOOOO MUCH sir.

[@joeyasro8785]

Clear and precise. Excellent presentation.

[@orthodium]

Nice encapsulation of a linear algebra course in little over an hour!

[@arunsharma-bv1wp]

I was badly searching for explanation on Dirac; Ket and Bra. I tried my level best to think of the significance. Why we do that? Why we use these notations? When you pointed out the question I was hopeful that may be I can get the answer. And here you are....I got it.. This looks reasonable..I appreciate..I am able to correlate it with now Spin Quantum States explained by Stern and Geralch ..I wish you will have answers for my future doubts..Thank you so much for priceless lecture.

[@darkvision20666]

Never seen this explained so clearly. Many thanks.