「相互作用描像」の版間の差分

<!-- The [[density matrix]] can be shown to transform to the interaction picture in the same way as any other operator. In particular, let <math>\rho_I</math> and <math>\rho_S</math> be the density matrix in the interaction picture and the Schrödinger picture, respectively. If there is probability <math>p_n</math> to be in the physical state <math>|\psi_n\rang</math>, then --><math display="block">\begin{align} \rho_\mathrm I(t) &= \sum_n p_n(t) |\psi_{n,\mathrm I}(t)\rang \lang \psi_{n,\mathrm I}(t)|

{{Indent|<math>\rho_\mathrm I(t) = \sum_n p_n(t) |\psi_{n,\mathrm I}(t)\rang \lang \psi_{n,\mathrm I}(t)| &= \sum_n p_n(t) e^{i H_{0,\mathrm S} t / \hbar}|\psi_{n,\mathrm S}(t)\rang \lang \psi_{n,\mathrm S}(t)|e^{-i H_{0, \mathrm S} t / \hbar} \\
&= e^{i H_{0, \mathrm S} t / \hbar} \rho_\mathrm S(t) e^{-i H_{0, \mathrm S} t / \hbar}</math>}}