The density matrix refers to the quantum mechanical analogue to a phase space probability measure in the classical statistical mechanics.

It is a Hermitian positive-semidefinite matrix of trace one that describes the statistical state of a quantum system.

Hermitian matrix is defined as A=A^(dagger). Meaning that NxN matrix A is equal to it's transposed complex conjugate.

Trace is defined as adding all the terms on the diagonal.

Measurements in quantum physics helps us understand the density matrix of quantum-mechanical systems.

The Matrix

The Matrix Reloaded

The Matrix Revolutions

There are three Matrix movies: The Matrix, The Matrix Reloaded, and The Matrix Revolutions. There are also a series of short animated films called The Animatrix.

All movies on TopRater: toprater.com/en/movies/objects/2867535-the-matrix-1999