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.

Scalable, coherent many-body systems can enable the realization of previously unexplored quantum phases and have a potential to exponentially speed up information processing. Here we report the cooling of a quantum simulator with ten thousand atoms and mass production of high-fidelity entangled pairs. In a two-dimensional plane, we cool Mott-insulator samples by immersing them into removable superfluid reservoirs, achieving an entropy per particle of 1.9−0.4+1.7×10−3kB. The atoms are then rearranged into a two-dimensional lattice free of defects. We further demonstrate a two-qubit gate with a fidelity of 0.993(1) for entangling 1250 atom pairs. Our results offer a setting for exploring low-energy many-body phases and could enable the creation of large-scale entanglement.

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