At some point you will have to learn about second quantization and all the stuff that can be done with it. I was alternately charmed and horrified by Feynman's Statistical Mechanics, and his Chapter on Annihilation and Creation Operators is good start on second quantization. (It's an old book, so some things are done more cleanly now, but it's Feynman, so you know it's going to be good.) After that, I suggest a serious book on Quantum Optics. I especially like Chiao and Garrison. And you need to learn Quantum Optics anyway, so that you can walk and breathe correctly. I think it's arduous and weird, but necessary.