  We study the quantum spin dynamics of a frustrated XXZ model on a pyrochlore
lattice by using large-scale quantum Monte Carlo simulation and stochastic
analytic continuation. In the low-temperature quantum spin ice regime, we
observe signatures of coherent photon and spinon excitations in the dynamic
spin structure factor. As the temperature rises to the classical spin ice
regime, the photon disappears from the dynamic spin structure factor, whereas
the dynamics of the spinon remain coherent in a broad temperature window. Our
results provide experimentally relevant, quantitative information for the
ongoing pursuit of quantum spin ice materials.
