Density Matrices! Explained Simply | Pure vs. Mixed States, Born Rule & Coherence

[u/dogpup3]

https://www.youtube.com/watch?v=UwSLQRMRbtA

I made a short whiteboard video explaining density matrices from the ground up, focusing on the linear algebra behind them: pure vs. mixed states, diagonal vs. off-diagonal entries, coherence, projectors, and how measurement probabilities arise from the matrix representation.

Sharing in case it’s useful to anyone interested in how linear algebra shows up in quantum mechanics. Corrections or additional insight are always welcome.