4. Spin One-half, Bras, Kets, and Operators

MIT 8.05 Quantum Physics II, Fall 2013
Instructor: Barton Zwiebach

In this lecture, the professor talked about spin one-half states and operators, properties of Pauli matrices and index notation, spin states in arbitrary direction, etc.

License: Creative Commons BY-NC-SA

[tripp]

this is insane the amount of detail he goes into. What a great resource. Thank you MIT and Dr Zwiebach

[muckrakerwm.]

This lecture by professor Zwiebach at MIT is very clear and to the point about Dirac notation for matrix mechanics in quantum mechanics. Do not believer the topic could be made any clearer. Great lecture. Learn a lot....

[kiara]

I fell asleep with another Youtube video and I woke up 20 min ago to this video. I don't know how I got here, just know now I have 20 min watching this dude and finally feel awoke enough to acknowledge it

[a.c.e]

For anyone interested, minute 45:00 is essentially the mathematical proof of how you can decompose ANY Hermitian operators into the pauli sigma operators, where in the video Sx is actually the Pauli-x gate, Sy is the Pauli-y gate, Sz is the Pauli-z gate and Identity is the identity/idle (id) gate. It's something that is immensely useful when working with Quantum Circuits and the entirety of Quantum Evolutions using unitaries and hamiltonians, and not really explained much in most books. Hope you like it!

[TheLocalSexOffender]

This is amazing, honestly helped so much with quantum mechanics course. Shows the difference a lecturer can make.

[jackbradley]

i love this guy. i originally didnt like his voice but ive began to love it. Ive never seen concepts explained so clearly and coherently. He also sounds like admiral general adam from the movie the dictator. Dont take this the wrong way as both these voices are legendary. Jokes aside thank you MIT for all these free lectures theyve changed my life and education.

[juliamay]

I can't thank you enough for these lectures. It's just that I can't understand my teacher sometimes and this channel comes to save my life.

[AnsImran]

Tears of joy in my eyes!
Thanks Barton Zweibach! You are the best!

I was really having a hard time solving a problem, related to (n . sigma), I knew the notation was shitty, but my professor insisted there was nothing shitty about it, and did not explain anything about the shit at all.
Thanks to Barton Zweibach, I now know all the shit about (n . sigma)!

[tondog]

Seems so trivial now. I wish I had this 20 years ago. Great lecture

[afifakimih]

very detail lectures yet every single word he explained are crystal clear...tnx & ❤ MIT, Tnx & ❤ Dr.Zwiebach.!!❤❤❤🇧🇩🇧🇩

[hongyuzhang]

55:18 shout out to the cameraman who actually pays attention 🎉

[Name-jwsj]

I see a lot of positive comment directed at professor Zwiebach, but the real all star is the camera person. The camera person did an excellent job.

[Boooommerang]

Thanks for this class, Professor! Really thanks. It was the best explanation I've seen in years! Congratulations

[maazadnan]

great work by the camera man 🎥; done a really great job in this video 👍🏻

[andreiasimov]

This lecture was awesome!!, I totally got some things neither my professors or books talked about in detailes. Thank you very much ;D

[岡安一壽]

I think that an electron has shift in coordinate (1/2π)msλ in r-direction. (ms:spin quantum number, λ:wave-length)
Accordingly, the angular momentum is
(De Broglie equation: p=h/λ)
And the magnetic moment is
(area)･(electric current)＝{πr (q/2m)L+2(q/2m)S.
Thus, we can know that the g-factor for spin angular momentum is equal to 2.
I'm sorry that I'm not good at English.

[jairodr]

He is from my university in Peru, in his career he used to get the highest and perfect marks

[tag_of_frank]

41:00 is the most hand-wavey thing I have ever heard -> "remove something to do with the identity because otherwise Si will commute with everything"

[ytsas]

Whoever transcribes this, the symbol at 35:30 to 35:40 is the Levi-Civita symbol.
55:30 - they're Pauli matrices, not poly or power matrices.

[quahntasy]

I find these lectures much better than the ones by alan adams.