Definition 1.1. A density matrix ρ is a matrix representing the density operator with the
conditions:
- The trace of ρ is 1.
- ρ is a positive-semidefinite matrix
References
[1] MIT OpenCourseWare, 8.371J Quantum Information Science, Spring 2006.
[2]Blum, Karl, Density Matrix Theory and Applications. 2nd edition Springer, 1996.
