Intermediate-level QM book aimed on foundational issues

[carlosbgois]

Hey there! While considering going into foundational issues in QM (reading abou entanglement and Bell's theorems now), I realized I may need a better grasp of QM. I have studied both Griffiths' and Cohen-Tannoudji's (both volumes, excluding the appendices) books. I am not very confident in my understanding, though.

Thence I ask for book suggestions that would take me to higher level, while also pointing me towards the discussion of foundational issues, maybe quantum information theory also. My university uses Sakurai's book on the master's QM course, but I skimmed through it and it didn't seem to discuss a lot of more philosophical issues. I have found sparse recommendation of Ballentine's textbook, but got afraid it would be written defending his position on the matter in a biased way. Couldn't find many comments about his book around, neither anyone who read it.

If you please, then, I'd really appreciate any suggestions on which way to go, especially if you could explain me the why of your recommendation.

 

[Demystifier]

Ballentine is a great advanced book, except that it somewhat misinterprets issues related to collapse.
Another great book emphasizing foundations, at a lower level than Ballentine, is Schumacher and Westmoreland, Quantum Processess, Systems and Information.

 

[carlosbgois]

Your second suggestion, the one by Schumacher and Westmoreland, looks like exactly what I was looking for. Thank you! I am still interested in further suggestions, if anyone else would please.