Uhlmann A. An Energy Dispersion Estimate (9K, LaTeX) ABSTRACT. Given the density operator $\varrho_1$ as an initial value of an Hamiltonian motion that evolves in a time interval $\Delta t$ to $\varrho_2$. Let $\Delta E$ be the energy dispersion (or energy uncertainty) of the motion. Then $\Delta t \, \Delta E$ can be estimated from below by comparing the length of the Hamiltonian curve with a geodesic joining the initial and the final density operator. The lengths are calculated in the Bures metric.