21. Nevertheless, the density matrix contains all the information necessary to calculate any measurable property of the mixed state. 22. In rough analogy, a POVM is to a PVM what a density matrix is to a pure state. 23. In this case, the diagonal components of the density matrix become negligible after introducing the thermal distribution function, 24. This demonstrates that, as expected, the reduced density matrix for an entangled pure ensemble is a mixed ensemble. 25. The density matrix can be shown to transform to the interaction picture in the same way as any other operator. 26. Using this concept, in conjunction with the density matrix he extended the classical concept of entropy into the quantum domain. 27. The Lindblad equation in quantum mechanics is a generalization of the master equation describing the time evolution of a density matrix . 28. That is, ? can have a definition somewhat broader than that of a density matrix ; the theorem still holds. 29. In the Heisenberg picture, the density matrix does not change with time, but the operators are time-dependent. 30. The trace-class operator " W " can be interpreted as the density matrix of a quantum state.
