Without a Trace | Trace Adkins | Gym Class Heroes | class action | class | Class A | working class | DB Class 218 | Class War | British Rail Class 37 | Trace Bundy | Social class | British Rail Class 47 | Victorian Railways X class | GWR 3031 Class | Class D | British Rail Class 66 | World Class Championship Wrestling | Saved by the Bell: The New Class | Nimitz-class aircraft carrier | Middle Class Rut | Middle class | middle class | Mercedes-Benz G-Class | Master Class | master class | LNER Class A4 4468 Mallard | First class travel | Class Act | Class 66 |
A density matrix is a Hermitian, positive semi-definite matrix of trace one.