# Density matrices as polarization vectors

@article{Fano1995DensityMA, title={Density matrices as polarization vectors}, author={Ugo Fano}, journal={Rendiconti Lincei}, year={1995}, volume={6}, pages={123-130} }

The concept of a density matrix originated about 1930 in the process of adapting to quantum mechanics the statistical descriptions of classical phenomena. A new light was cast on this concept when Felix Bloch formulated his NMR equation, inclusive of dissipative terms: This equation, ostensibly the time-dependent Schrödinger equation for a spin’s density matrix, governs in fact the expectation values of evolving observables, namely, the components of the spin’s polarization vector. It serves…

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