Quantum Computation and Quantum Information, Michael A. Nielsen, Isaac L. Chuang, 2010 (Cambridge University Press)DOI: 10.1017/CBO9780511976667 - A comprehensive textbook foundational to quantum computing and information, covering density matrices, open quantum systems, and their applications.
Quantum Computation, John Preskill, 2021 (California Institute of Technology) - Highly regarded lecture notes providing a rigorous treatment of quantum mechanics and quantum information, including detailed discussions of density matrices and mixed states.
Machine Learning with Quantum Computers, Maria Schuld, Francesco Petruccione, 2021 (Springer International Publishing)DOI: 10.1007/978-3-030-83098-4 - A foundational textbook on quantum machine learning, illustrating how density matrix formalism is applied in QML, particularly for noise modeling and algorithm design.
Barren plateaus in quantum neural network training landscapes, Jarrod R. McClean, Sergio Boixo, Vadim N. Smelyanskiy, Ryan Babbush, and Hartmut Neven, 2018Nature Communications, Vol. 9DOI: 10.1038/s41467-018-07090-4 - A seminal paper introducing the concept of barren plateaus in variational quantum algorithms, where density matrix properties and information geometry play a role in understanding the vanishing gradients.