Crash course in density matrices

Hi everyone,

Jonathon Riddell here. Today we do a crash course of density matrices in quantum mechanics. This should be enough to get us started in statistical mechanics!

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Around the 7 minute mark my camera covers up a 4, but the density matrix is identical to the equation that appears at the 7m 45s mark!

Recommended textbooks:
Quantum mechanics:
Statistical mechanics:
Quantum information:

[themorrigan]

Thank you for this Ive been studying entanglement and density matrices are involved and Im happy to see this

[david]

I like this because it's minimal: it seems to say all the basics about density matrices in a clear way. However, for me that assessment must be balanced by the fact that I couldn't follow any of this, probably because I'm not familiar with it and have not worked out any algebraic problems using any of these operators. I do look forward to learning this stuff someday, as it's obviously a lot simpler than actually trying to use the Schrödinger equation directly to reason about QM systems. I'm a follower of the Bohm theory and I'd like to be able to actually follow its mathematics somehow, given the fact that I never learned QM in any of my undergraduate physics classes from the 1960s. In particular, I'd like to be able to apply Bohm not just to the double slit, but to Stern-Gerlach spin measurements, too. I think that would actually be a bit simpler.

[f_add_mebowshot]

thx for the nice explanation and greetings to your cat

[petrus]

can you make a video how to treat a time dependent hamiltonian in various fashions?

[mirphy]

very much interesting lectures. Please mention the name of book from where the lecture have been taken

[pois-securitypathshala]

PLease explain what every step means in physics? like why tr(rho square ) should be less than 1 for mixed states, etc

[billy-cgqq]

Lol, what are the prerequisites for taking this lesson? I don't understand a thing

[preethamkumar]

Wrong formula written in the thumbnail of the video

[ty]

Can’t give any intuition bro… … ? You reiterate text book formalism without context.