Quantum coherence now measured in mechanical systems

Researchers have found evidence of genuine multipartite entanglement involving between 105 and 107 atoms within recent mechanical superposition states. Benjamin Yadin of Universität Siegen and Matteo Fadel of Peking University and ETH Zürich developed new measures, “extensive size” and “entangled size”, to quantify macroscopic quantum coherence, moving beyond previously less rigorous approaches. These measures, grounded in quantum information theory, allow for a transparent comparison of experiments ranging from micro-mechanical oscillators to diffracting molecules, and directly estimate coherence and entanglement from experimental data. The work demonstrates a method for assessing how well experiments probe the large-scale limits of quantum mechanics. Recent…