# 7: The Density Matrix

- Page ID
- 5662

- 7.1: The Density Matrix
- A density matrix is a matrix that describes a quantum system in a mixed state, a statistical ensemble of several quantum states.

* Thumbnail: measured density matrix of a thermal state. Image used with permission (CC SA-BY 3.0 unported; measured density matrix of a thermal state).*

### Contributors

- Michael Fowler (Beams Professor, Department of Physics, University of Virginia)