Measuring the universal scaling of many-body entanglement (Dr. P. Hauke)

A major obstacle, however, is the difficulty of observing many-body entanglement. We show that the quantum Fisher information, a witness for genuinely multipartite entanglement, is equivalent to routinely measured response functions such as the dynamical susceptibility. This equivalence is independent from microscopic details. Moreover, we derive the universal scaling of the quantum Fisher information, and illustrate it at three examples, the Mott-insulator–superfluid transition of hard-core bosons, and the Ising model in a transverse field with nearest-neighbor as well as infinitely-ranged interactions. Our work makes multipartite entanglement accessible to experiments studying quantum phase diagrams at nonzero temperatures, most importantly also in the context of solid-state samples.