Quantum MechanicsThe Nitty-gritty

Have you yet been introduced to density matrices, mixed states, and classical probabilities in QM? Professor Reinhold Bertlmann has some lecture notes with a good introduction to the density matrix.

Density Matrices by Reinhold Bertlmann

Professor Frederic P. Schuller has a lecture series where he talks about Quantum Mechanics from a very precise, mathematical, point of view. Definition, theorem, proof.

Frederic Schuller teaches QM